干燥后褐煤水分复吸性的试验研究

在实验室条件下考察了深度干燥和轻度干燥后的褐煤在高湿度环境和自然环境中的水分复吸性。结果表明:干燥后褐煤由于自身特点,具有较大的吸水能力,但受环境条件的影响比较显著,深度干燥后的褐煤水分复吸性较强,当干燥后褐煤处于不同的湿度环境下,或复吸水分或复失水分,但最终将会趋于某一稳定水分值。建议工业化干燥过程中,干燥后褐煤的含水量略大于内含水量,当处于正常自然环境中,干燥后褐煤不会发生显著的水分复吸现象,过度干燥既不经济也无必要。

褐煤腐植酸的抽提及其对褐煤吸水性能的影响

褐煤腐植酸含量高,腐植酸中含有多种活性基团,在工业、农业、畜牧业等领域有多种用途。褐煤直接燃烧利用率不大,因此在开发利用褐煤资源前对其进行腐植酸抽提是一种较好的提质方式。本文采用碱浸法对褐煤进行腐植酸的抽提,研究了煤样粒度、抽提条件等因素对腐植酸抽提率的影响,以及干燥的原煤、腐植酸抽提残煤和脱灰煤的水分复吸性能。结果表明:粒度在0.2mm以下的煤样,在超声波条件下抽提腐植酸效果较好;抽提残煤水分复吸率明显高于原煤,但将抽提残煤脱灰处理后,水分复吸率有明显下降,且与原煤脱灰后吸水性能相近,说明抽提残煤的吸水性与煤的孔隙率及表面的极性官能团有关,特别是碱浸法抽提腐植酸时生成的强吸水性羧酸盐类对抽提残煤吸水性有显著影响。

芒来煤矿褐煤改性提质试验研究

利用带式炉改性提质工艺,脱除影响芒来褐煤热值的水和部分含氧官能团,使褐煤的发热量组分富集,热值提升,达到中高热值燃料煤(≥20.9 MJ/kg)指标。

Magnetic and microwave absorbing properties of M-type barium ferrite/graphene oxide composite microwave absorber

In order to improve the absorbing properties of M- type barium ferrite absorbing materials, M-type barium ferrite/graphene oxide composites with different graphene oxide contents were synthesized by the sol-gel autocombustion method. X-ray diffraction （XRD）, a scanning electronic microscopy （ SEM ）, a physical properties measurement system （PPMS-9）, and a vector network analyzer were used to analyze their structure, surface morphology, magnetic and absorbing properties, respectively. The results show that the absorbing band of the composite absorbing material is widened and the absorbing strength is increased compared with the pure M-type barium ferrite. The sample with the content of doped graphene oxide of 3% has the minimum reflectivity at 10 to 18 GHz frequencies. Hence, the doped graphene oxide effectively improves the absorbing properties of M-type barium ferrite.

Effects of thermal oxidation on microwave-absorbing and mechanical properties of SiC_f/SiC composites with PyC interphase

The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.

Effects of Different Fertilization Treatments on Biological Activity of Reclaimed Soil

As per randomized block design, the research had different fertilizer treatments, and the organic matter, respiration, enzyme activity and microbial carbon and nitrogen in reclaimed soil were studied. Fertilization schemes were as follows： The treatment without fertilizers（CK）, the treatment with chemical fertilizers（C）, the treatment with chemical fertilizers and bacterial fertilizer（CB）, the treatment with organic fertilizer and chemical fertilizers（CM）, and the treatment with chemical fertilizers, organic fertilizer and bacterial fertilizer（CMB）. The results showed： Four fertilization treatments could improve the content of soil organic matter. CMB, CM and CB could significantly improve the soil respiration. Organic fertilizer and fertilizer could significantly improve soil enzyme activity, In different growth stages the CMB treatment had highest urease and phosphatase.The most significant in the treatment content of sucrose was CM. Organic fertilizer and microbial fertilizer can significantly improve the microbial carbon and nitrogen in soil. For the microbial biomass carbon, the CMB treatment increased by 11%-34% than CB treatment, and 35%-63% than C treatment. In terms of microbial nitrogen CMB, CM respectively increased by 31%-51% than CB treatment, and 52%-100% compared with C. In the process of land reclamation, we should combine the organic fertilizer, microbial fertilizer and inorganic fertilizer. Only in this way can soil biological activity be accelerated, soil microbial environment improved, and the ripening increased soil nutrient and soil cultivation be enhanced.

Removal of Cu(Ⅱ) from Aqueous Solution Using a Novel Crosslinked Alumina-Chitosan Hybrid Adsorbent

A novel biosorbent was developed by coating chitosan, a naturally and abundantly available biopolymer, on to activated alumina based on oil shale ash via crosslinking. The adsorbent was characterized by various techniques, such as Fourier transform infrared spectroscopy, scarming＇ elec.tron micros cop.y, the rmogravimetric-differentialthermal analysis, and X-ray photoelectron spectroscope. Batch isothermal equilibrium adsorption experiments were condcted to evaluate the adsorbent for the removal of Cu（Ⅱ） from wastewater. The effect of pH and agitation time on the adsorption capacity was also investigated, indicating that the optimum pH was 6.0. The equilibrium adsorp-tion data were correlated with Langmuir and Freundlich models. The maximum monolayer adsorption capacity of chitosan coated alumina sorbent as obtained from Langmuir adsorption isotherm was fotmd to be 315.46 mg.g-1 for Cu（Ⅱ）. The adsorbent loaded with Cu（Ⅱ） was readily regenerated using 0.1 mol.L-1 sodium hydroxide solution. All these indicated that chitosan coated alumina adsorbent not only have high adsorption activity, but also had good stability in the wastewater treatment process.

Preparation, characterization and salt-resistance of a coal based super absorbent composite

Potassium humate was extracted from brown coal. A novel super absorbent composite, poly （acrylic acid-co-acryla- mide）/potassium humate （PAA-AM/KHA）, was prepared by graft polymerization of acrylic acid, acrylamide and coal based potassium humate using N, N＇-methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator. The effects of reaction temperature, degree of neutralization of the poly （acrylic acid） and the amounts of crosslinker, initiator and potassium humate were investigated. Salt resistance tests were also carded out. The composite prepared under optimal conditions had a potassium bumate content of 10% and exhibited a water absorption of 770 g/g in distilled water, and 349, 286 and 41 gig in 0.5 mol/L KC1, MgC12 and A1CI3 solutions respectively. The results indicate that the salt resistance of PAA-AM/KHA was superior to that of poly （acrylic acid-co-acrylamide） because of the collaborative effect of functional groups of the coal based potassium humate. The PAA-AM/KHA micro powder was characterized by IR spectroscopy and the micrographic surface was characterized by scanning electron microscopy. Introduction of potassium humate into the poly （acrylic acid-co-acrylamide） structure creates a composite more suitable for use as a water-managing material in the renewal of arid and desert environments. The salt resisting property of the composite is improved, production costs are reduced and the growth stimulant effect is still present.

Effects of superabsorbent polymer particles on flexural properties and self-healing behavior of ECC

In order to improve the self-healing behavior and the recovery of mechanical properties of engineered cementitious composites(ECC),the approach of incorporating superabsorbent polymer(SAP)in mixtures is investigated.The rapid water penetration test and four-point bending test were conducted to evaluate the effects of self-healing on the water permeability and mechanical properties of pre-damaged ECC.The self-healing process and self-healing products were observed by the environment scanning electron microscope(ESEM)and energy dispersive X-ray spectroscopy(EDS).The experimental results show that all ECC mixtures exhibit excellent flexural capacity,meanwhile maintaining a crack width below 50μm.The incorporation of SAP particles in ECC can apparently improve the mechanical recovery of ECC mixtures after 10 healing curing cycles,such as flexural deformation and flexural stiffness.The flexural stiffness of ECC containing 4%SAP particles after self-healing can be recovered to 80%.The self-healing test results show that when the water permeability of ECC mixtures incorporating SAP particles is close to zero,only three healing cycles are needed.When ECC incorpora ting more SAP particles,the accelerated self-healing process can be finished in the first three cycles,and self-healing product is mixed Ca(OH)2/CaCO 3 with CaCO 3 being a major component in the later stage.It is,therefore,feasible to produce ECC materials incorporating SAP particles,while simultaneously maintaining higher material ductility and self-healing behavior.

Physical and Hydrodynamic Properties of Spherical Cellulose-Titanium Dioxide Composite Matrix for Expanded Bed Adsorption

Expanded bed adsorption (EBA) has been widely used in industrial downstream bioprocessing. Solid matrix is the principal pillar supporting the successful application of EBA. A novel spherical cellulose-titanium dioxide composite matrix was prepared through the method of water-in-oil suspension thermal regeneration. Its typical physical properties were wet density 1.18g.cm-3, diameters in the range of 100-300um, porosity 85.5%, and water content 72.3%. Expansion characteristics and liquid mixing performance of the matrix in expanded bed were investigated using water and 10% (by mass) glycerol solution as mobile phases. The results indicate that the custom-assembled matrix has a stable flow hydrodynamics and exhibits the same degree of liquid-phase mixing or column efficiency as the commercially available Streamline adsorbent.

Characterization and adsorption behaviors of a novel synthesized mesoporous silica coated carbon composite

A novel mesoporous silica coated carbon composite(denoted SEG) with hierarchical pore structure has been successfully prepared in an aqueous solution that contains triblock copolymer template, aluminum chloride, siliceous source and expanded graphite. Textural property and morphology of the SEG composite were characterized by the combination of X-ray diffraction, N_2 adsorption–desorption, scanning electron microscopy,transmission electron microscopy and Fourier transform infrared measurements. Results show that mesoporous silica is steadily and uniformly grown on the surface of the graphite slices and the thickness of the silica layer can be finely tuned according to the silica/C molar ratio in the initial reaction solution. This newly synthesized SEG composite shows greatly increased adsorption capacity to methylene blue than the pristine expanded graphite in the batch tests. Both Langmuir and Frendlich models were further used to evaluate the adsorption isotherms of methylene blue over expanded graphite and SEG samples with different silica contents. Finally, pseudosecond-order model was used to describe the kinetics of methylene blue over expanded graphite and the silica-carbon composites.

Synthesis and evaluation of carbon nanotubes composite adsorbent for CO2 capture： a comparative study of CO2 adsorption capacity of single-walled and multi-walled carbon nanotubes

As a preliminary investigation towards obtaining carbon nanotube composite adsorbent for CO2 capture, in this study CO2 adsorption performance of three commercial carbon nanotubes （CNTs） one single-walled carbon nanotubes （SWCNTs）, and two （2） different multi-walled carbon nanotubes （referred to as A-MWCNTs and B-MWCNTs） were evaluated and compared. The purpose of this study was to compare the different types of CNTs and select the best to serve as the solid anchor in the development of a hydrophobic composite adsorbent material for CO2 capture. The N2 physi- sorption of the CNTs was conducted to determine their surface area, pore volume and pore size. In addition, morphology and purity of the CNTs were checked with Transmission Electron Microscopy and Raman Spectroscopy, respectively. The CO2 adsorption capacity of the CNTs was evaluated using Thermo-gravimetric analysis （TGA） at 1.1 bar, at operating temperature ranged from 25 to 55 ~C and at different CO2 feed flow rates, in order to evaluate the effects of these variables on the CO2 adsorption capacity. The results of CO2 adsorption with the TGA show that CO2 adsorption capacity for both SWCNTs and MWCNTs was the highest at 25 ~C. Changing the CO2 flowrates had no significant effect on the adsorption capacity of MWCNTs, but decreasing the CO2 flow rate resulted in the enhancement of the CO2 adsorption capacity of SWCNTs. Overall, it was found that the SWCNTs displayed the highest CO2 adsorption capacity （29.97 gCO2/kg ad- sorbent） when compared to the MWCNTs （12.09 gCO2/kg adsorbent）, indicating a 150% increase in adsorption capacity over MWCNTs.

Characteristics of Phosphorous Adsorption and Desorption by Organo-Mineral Colloidal Complexes of Purple Paddy Soils

The kinetic characteristics of P adsorption and desorption by organo-mineral colloidal complexes (OMC)were studied using acid, calcareous and neutral purple paddy soils taken from Chongqing and Sichuan, China.The results showed that the P adsorption capacity of the organo-mineral colloidal complexes differed with the soil types, being higher for the acid and calcareous purple soils than for the neutral purple soils. Partial removal of the organic matter increased the adsorption capacity of the colloidal complexes. A very significant positive correlation was found between the amounts of P desorbed from OMC and the P saturation degrees.The P adsorption reaction was quick at the early stage and slowed later. The raise of temperature increased P adsorption capacity and P adsorption rate of the colloidal complexes. The adsorption processes could be described by the Elovich equation.

Synthesis of magnetically modified palygorskite composite for immobilization of Candida sp. 99–125 lipase via adsorption

Magnetically modified palygorskite composites were synthesized with γ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac- tion, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99-125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5 mg· g^-1 support and enzyme activity of 2631.6 U· （g support）^-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusabilitV compared with free lipase.

Clinical Observation on 46 Cases of Infantile Repeated Respiratory Tract Infection Treated by Mild-Moxibustion over Acupoints on Back

Repeated respiratory tract infection is a frequently-occurring disease during childhood. At present, western medicine doctors generally adopt anti-infectives and immunomodulators to treat the disease, while traditional Chinese medicine doctors mainly administer decoction of Chinese herbs. The authors treated 46 cases of repeated respiratory tract infection from March 1990 to April 1996 by applying mild-moxibustion over points on the back with satisfactory therapeutic results. A report follows.Clinical Data All the 86 cases were outpatients in our hospital with duration of common cold for over 10 days and characterized by relapse of respiratory tract infection. There were over 7-time relapse of respiratory tract infection on each case within a year. Eighty-six cases were randomly divided into treatment group (46 cases) and control group (40 cases). Of the 46 cases in the treatment group, 22 were boys and 24 girls. 17 cases (36.9%) were 6 months to 4 years old, 18 (39.1%) 4 to 6 years, and 11 (23.9%) 6 to 12 years. Among the 40 cases in the control group, 19 cases were boys and 21 girls.

Collision performance of bitubular tubes with diaphragms

A numerical study of bitubular tubes with diaphragms compared with single and bitubular tubes subjected to dynamic axial impact force was presented. At first, the energy absorption response of the composite structure under axial loading was analyzed by finite element simulation. The results show that the efficiency of energy absorption can be improved by introducing diaphragms to the double-walled columns. Then, the effect of the amount and location of diaphragms, the shape and the size of the inner tubes, and the thickness of the composite structures were also studied numerically. The collision performance of the composite structure is affected by the deformation of diaphragms, as well as the interaction of outer and inner tube. The non-uniform distribution of diaphragms can improve the energy absorption efficiency of structures for a constant number of diaphragms. The specific energy absorption of the hexagonal inner tube is the highest, followed by the circular, octagonal and square ones.

Infrared emissivity and microwave absorbing property of epoxy-polyurethane/annealed carbonyl iron composites coatings

The microwave absorption property and infrared emissivity have been investigated for the single-layer coating made of the epoxy-polyurethane resin and carbonyl iron powders with variation of annealing treatment. Microwave-absorbing property was investigated by measuring the complex permittivity and complex permeability of the absorber in the frequency range from 2 to 18 GHz. Infrared emissivity value was measured using IR-2 Infrared Emissometer in the wavelength range of 8-14 μm. After annealing, the Fe （110） peak became sharp, and the crystallization improved significantly. Annealing treatment could reduce the sttrface energy of powders, improve compatibility between fillers and adhesives, and result in increase of the density of the coating. The lowest value of infrared emissivity （0.419） was obtained from the coating made of the carbonyl iron powder annealed at 700℃ for 1 h. With the variation of the annealing temperature, the magnetic and dielectric properties of the carbonyl iron particle were changed. The maximum reflection loss decreased and the matching frequency shifted to lower frequency with increasing the annealing temperature of carbonyl iron particles, which coincided with the variation of the complex permeability and permittivity according to the annealing temperature. Magnetic loss factor and dielectric loss factor of carbonyl iron particles were improved with increasing the annealing temperature in the 2-18 GHz range.

Low velocity impact response and energy absorption behavior on glass fibre reinforced epoxy composites

A study was undertaken to determine the effects of several key geometry influencing factors on the impact response and energy absorption behavior of the glass fibre reinforced epoxy composites at low and intermediate energies.The energy-balance model was employed for characterising the energy absorption behavior and it depends strongly on the plate diameter and thickness.In addition,the damage vs.energy and force maps is effective in monitoring damage growth within the composite panel.The response of the composite laminate configurations characterized by different stacking sequences subjected to low velocity impacts with different impact energies have also been studied to estimate the damage initiation of composites.

Complex Permittivity and Microwave Absorbing Property of Si_3N_4-SiC Composite Ceramic

Si3N4-SiC composite ceramics were fabricated by chemical vapor infiltration using porous Si3Na ceramic as preform. The average grain size of SiC was 30 nm. Relationship between SiC content and relative complex permittivity of Si3Na-SiC within the frequency range of 8.2-12.4 GHz （X-band） was investigated. The average real part of relative complex permittivity ε′ of Si3N4-SiC increased from 3.7 to 14.9 and the relative imaginary part ε″ increased from 0.017 to 13.4 when the content of SiC increased from 0 to 10 vol.%. The Si3N4-SiC ceramic with 3 vol.% SiC achieved a reflection loss below -10 dB （90% absorption） at 8.0-11.4 GHz, and the minimum value was -27.1 dB at 9.8 GHz when the sample thickness was 2.5 mm. The excellent microwave absorbing abilities of Si3N4-SiC ceramic were attributed to the interfacial polarization at interface between Si3N4 and SiC and at grain boundary between SiC nanocrystals.

Factors associated with a SARS-CoV-2 recurrence after hospital discharge among patients with COVID-19:systematic review and meta-analysis

Background:The proportion of recurrences after discharge among patients with coronavirus disease 2019(COVID-19)was reported to be between 9.1%and 31.0%.Little is known about this issue,however,so we performed a meta-analysis to summarize the demographical,clinical,and laboratorial characteristics of non-recurrence and recurrence groups.Methods:Comprehensive searches were conducted using eight electronic databases.Data re-garding the demographic,clinical,and laboratorial characteristics of both recurrence and non-recurrence groups were extracted,and quantitative and qualitative analyses were conducted.Results:Ten studies involving 2071 COVID-19 cases were included in this analysis.The proportion of recurrence cases involving patients with COVID-19 was 17.65%(between 12.38%and 25.16%)while older patients were more likely to experience recurrence(weighted mean difference(WMD)=1.67,range between 0.08 and 3.26).The time from discharge to recurrence was 13.38 d(between 12.08 and 14.69 d).Patients were categorized as having moderate severity(odds ratio(OR)=2.69,range between 1.30 and 5.58),while those with clinical symptoms including cough(OR=5.52,range between 3.18 and 9.60),sputum production(OR=5.10,range between 2.60 and 9.97),headache(OR=3.57,range between 1.36 and 9.35),and diz-ziness(OR=3.17,range between 1.12 and 8.96)were more likely to be associated with recurrence.Patients pre-senting with bilateral pulmonary infiltration and decreased leucocyte,platelet,and CD4+T counts were at risk of COVID-19 recurrence(OR=1.71,range between 1.07 and 2.75;WMD=?1.06,range between?1.55 and?0.57,WMD=?40.39,range between?80.20 and?0.48,and WMD=?55.26,range between?105.92 and?4.60,respectively).Conclusions:The main factors associated with the recurrence of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)after hospital discharge were older age,moderate severity,bilateral pulmonary infiltration,laboratory findings including decreased leucocytes,platelets,and CD4+T counts,and clinical symptoms including cough,sputum production,headache,and dizziness.These factors can be considered warning indicators for the recurrence of SARS-CoV-2 and might help the development of specific management strategies.