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1.
J Environ Manage ; 351: 119684, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38056324

RESUMO

The continuous increase in building energy consumption, and the increasing types and quantities of solid waste have seriously hindered the rapid development of social economy. Therefore, reducing building energy consumption while realizing the recycling of waste has become the mainstream topic of environmental protection construction in the new era. An alkali-activated ultra-light foamed insulation material (AFIM) for building walls was prepared using EPS particles as lightweight aggregates. The effects of EPS dosage, particle size, and gradation on the compressive strength, dry density, thermal conductivity, and volumetric water absorption of AFIM were studied. The results showed that while ensuring good mechanical properties of AFIM, EPS particles can significantly reduce the dry density, thermal conductivity, and volumetric water absorption of AFIM. Excitingly, the optimal thermal conductivity and dry density of AFIM were 0.0408 W/(m·K) and 127.03 kg/m3, respectively. The microscopic morphology results showed that there was good compatibility between EPS particles and AFIM slurry, and the interface transition zone (ITZ) between them was dense and without obvious cracks. In addition, the feasibility of AFIM was evaluated from four aspects: performance, energy consumption, carbon emissions, and life cycle cost (LCC). It was encouraged that the performance of AFIM was comparable to that of traditional insulation materials, and showed significant advantages in energy conservation, emission reduction and economic benefits compared to traditional insulatin materials.


Assuntos
Materiais de Construção , Resíduos Sólidos , Estudos de Viabilidade , Reciclagem , Água
2.
Ecotoxicol Environ Saf ; 233: 113324, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-35193030

RESUMO

This work investigated the distribution and chemical fingerprints of 24 metals in particulate matter (PM) deposited in nonoccupational human lungs. Metals in the pulmonary PM can be grouped by the mean concentration as > 5 × 103 µg/g (Al/Fe/Ca/Mg/Zn), 1-5 × 103 µg/g (Ti/Ba/Pb/Mn), 0.2-1 × 103 µg/g (Cu/Cr/As/V) and < 100 µg/g (Ni/Sn/Cd/Sb). Three parameters (LFL, LR, EFP) were defined to predict different metal leaching behaviors. The leaching factor (LFL) of metals was 10-60 for Pb/Sb/Cd/Co/Cu and decreased to 1-2 for Ni/Cr/Mg/Al/Fe. Metals showed a divergent extent of lung retention (LR), including high retention (LR>10, Al/Cd/Cr/Ba/Ni/Ti/Sn/V/Sb), moderate retention (2 

Assuntos
Metais Pesados , Material Particulado , Monitoramento Ambiental , Humanos , Pulmão/química , Metais/análise , Metais Pesados/análise , Material Particulado/análise
3.
Environ Geochem Health ; 44(3): 979-991, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34131853

RESUMO

The enrichment of heavy metals in air-borne particulate matters poses a great threat to health. In order to understand the mineralogical characteristics and sources of heavy metals in atmospheric particulate matter in coal mining cities, PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 µm), PM10 (particulate matter with an aerodynamic diameter less than 10 µm) and TSP (total suspended particulates) were sampled from Huainan city, China in December 2016 and May 2017. The contents of heavy metals in TSP are the highest, while those in PM2.5 are the lowest. Zn, Mn, and Pb are the main components of heavy metals in Huainan atmospheric particulates. Straw burning activities may result in relatively higher atmospheric particulate matter content in summer than that in winter. The proportion of mineral particles in the studied particulate matters was the highest (40.79%), followed by soot aggregates (35.55%) and coal fly ash (19.74%). The results of energy spectrum analysis show that the main component of soot aggregates is C, and other contents are contributed by elements such as O and Si. Coal fly ash mainly contains C, O, Si, and a small amount of Al and Na. As, Cd, and Hg are the most easily enriched heavy metals. Industrial emissions, traffic discharges, coal combustion and dust emissions were found to be the main sources of heavy metals in atmospheric particulates.


Assuntos
Poluentes Atmosféricos , Metais Pesados , Poluentes Atmosféricos/análise , China , Cidades , Monitoramento Ambiental , Metais Pesados/análise , Material Particulado/análise , Estações do Ano
4.
Biol Pharm Bull ; 41(4): 510-523, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29607923

RESUMO

Microscopic examination of crude drug components has been the traditional method to identify the origin of biological materials. For the identification of components in a given mixture via microscopy, standard reference photographs of fragments derived from different organs and tissues of individual species are required. In addition to these reference photographs, a highly observant eye is needed to compare the morphological characteristics observed under the microscope with those of the references and to then identify the origin of the materials. Therefore, if other indexes are available to be coupled with microscope examination, the accuracy of identification would be significantly improved. Here, we prepared standard reference photographs for microscopic examination to identify powdered and fragmented materials in the crude drug "Quanxie" derived from individual organs of dried scorpion (Buthus martensii KARSCH). Since a remarkable characteristic of scorpion bodies is that they fluoresce under UV light, two methods to identify "Quanxie" were established, including fluorescence fingerprint analysis and microscopic fluorescent luminance imaging analysis. In the former, at least 0.1 g of powered materials was used, which could be recovered after the measurement, and in the latter, only small amounts of powders were used for microscopic examinations. Both methods could distinguish powders of "Quanxie" from those of other micro-morphologically similar crude drugs, namely, "Chantui," "Sangpiaoxiao," and "Jiangcan." The combination of these methods should improve the swiftness and accuracy of "Quanxie" identification.


Assuntos
Misturas Complexas/análise , Escorpiões , Animais , Fluorescência , Microscopia de Fluorescência , Fenótipo , Pós , Escorpiões/anatomia & histologia
5.
Pak J Med Sci ; 32(6): 1522-1527, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-28083057

RESUMO

OBJECTIVE: To evaluate the effects of diet control and Metformin on placental morphology in gestational diabetes mellitus (GDM). METHODS: After written informed consent 62 GDMs were enrolled. According to WHO criteria, 30 cases of GDMs with blood sugar level <130 mg/dl, were assigned Group B (2000-2500Kcal/day and 30 minute walk thrice weekly were kept on diet control and 32 cases of GDM with blood sugar level >130 mg/dl, assigned Group C were kept on diet with tablet Metformin,(500mg TDS) Finally 25 normal pregnant females were kept in Group A as control. After delivery placentae were preserved and evaluated for morphology. RESULTS: Heavy placentae with abundant villous immaturity, chorangiosis and syncytial knots in group B and fibrinoid necrosis and calcification in group C were seen. In group B versus A placental and cord width while in Group C versus A only cord width in gross morphology showed significant results. In group B versus A villous immaturity, chorangiosis, infarction and syncytial knots in light microscopy were present; similarly in B versus C placental width, chorangiosis and syncytial knots showed significant results, while in C versus A results were non-significant. CONCLUSION: Metformin produced beneficial effects on placental morphology being comparable to normal control in contrast to diet group.

6.
Polymers (Basel) ; 16(3)2024 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-38337273

RESUMO

This study examines a versatile polymer known as polysurfactant, which is synthesized by co-polymerizing flexible acrylamide and sodium acrylate hydrocarbon chain. The polymer serves as a backbone and possesses active functional groups. Notably, the polysurfactant exhibits superior plugging and flooding abilities compared to conventional polymers. The primary objective of this paper is to investigate the properties and oil displacement characteristics of the polysurfactant through indoor physical simulation experiments. The results demonstrate that the multi-branched structure of the polysurfactant enhances its ability to associate, leading to the formation of a unique spatial network structure. The inclusion of multi-branched structures notably amplifies the association effect. The critical concentration for the association is estimated to be around 800 mg/L, at which juncture the polysurfactant exhibits a viscosity retention rate surpassing 90% subsequent to shearing. Furthermore, this spatial network structure exhibits self-recovery capabilities after experiencing shear failure and displaying strong viscosity and shear resistance. In addition, the concentration of the polysurfactant can control the hydrodynamic feature size, which shows its adaptability in regulation and oil-repelling functions at reservoir permeabilities ranging from 500 to 2000 × 10-3 µm2 with resistance coefficients ranging from 108 to 320. During the microscopic oil displacement process, the polysurfactant exerts a significant impact on mobility control, while the elastic pull clearly demonstrates a commendable viscoelastic oil displacement effect. The polysurfactant exhibits a specific degree of emulsification capability towards crude oil, leading to the emulsion exhibiting typical pseudoplastic fluid characteristics. The utilization of emulsification transportation and emulsification blockage contributes to the enhancement of oil recovery. As a result, the polysurfactant exhibits multifaceted capabilities, encompassing profile control, flooding, and plugging, owing to its unique structural characteristics. Through the implementation of a field test focused on flooding in the Daqing Oilfield, a significant enhancement in the recovery rate of 10.85% is observed, accompanied by a favorable input-output ratio of 1:3.86, thereby generating significant economic advantages.

7.
Materials (Basel) ; 17(7)2024 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-38612071

RESUMO

To promote the resource utilization of steel slag and improve the production process of steel slag in steelmaking plants, this research studied the characteristics of three different processed steel slags from four steelmaking plants. The physical and mechanical characteristics and volume stability of steel slags were analyzed through density, water absorption, and expansion tests. The main mineral phases, morphological characteristics, and thermal stability of the original steel slag and the steel slag after the expansion test are analyzed with X-ray diffractometer (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TG) tests. The results show that the composition of steel slag produced by different processes is similar. The main active substances of other processed steel slags are dicalcium silicate (C2S), tricalcium silicate (C3S), CaO, and MgO. After the expansion test, the main chemical products of steel slag are CaCO3, MgCO3, and calcium silicate hydrate (C-S-H). Noticeable mineral crystals appeared on the surface of the steel slag after the expansion test, presenting tetrahedral or cigar-like protrusions. The drum slag had the highest density and water stability. The drum slag had the lowest porosity and the densest microstructure surface, compared with steel slags that other methods produce. The thermal stability of steel slag treated by the hot splashing method was relatively higher than that of steel slag treated by the other two methods.

8.
Polymers (Basel) ; 15(5)2023 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-36904366

RESUMO

Dyed wood is prone to photoaging when exposed to UV irradiation which decreases its decorative effect and service life. Holocellulose, as the main component of dyed wood, has a photodegradation behavior which is still unclear. To investigate the effect of UV irradiation on chemical structure and microscopic morphology changes of dyed wood holocellulose, Maple birch (Betulacostata Trautv) dyed wood and holocellulose were exposed to UV accelerated aging treatment; the photoresponsivity includes crystallization, chemical structure, thermal stability, and microstructure were studied. Results showed that UV radiation has no significant effect on the lattice structure of dyed wood fibers. The wood crystal zone diffraction 2θ and layer spacing was basically unchanged. With the UV radiation time extension, the relative crystallinity of dyed wood and holocellulose showed a trend of increasing first and then decreasing, but the overall change was not significant. The relative crystallinity change range of the dyed wood was not more than 3%, and the dyed holocellulose was not more than 5%. UV radiation caused the molecular chain chemical bond in the non-crystalline region of dyed holocellulose to break, the fiber underwent photooxidation degradation, and the surface photoetching feature was prominent. Wood fiber morphology was damaged and destroyed, finally leading to the degradation and corrosion of the dyed wood. Studying the photodegradation of holocellulose is helpful to understand the photochromic mechanism of dyed wood, and, further, to improve its weather resistance.

9.
Materials (Basel) ; 16(19)2023 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-37834693

RESUMO

In order to advance the utilization rate of multi-source solid wastes in the Ningxia region of China, 16 groups of pavement base mixtures were designed with cement and fly ash (FA) as binders, steel slag (SS), silicon manganese slag (SMS), and recycled crushed stone (RCS) as composite aggregates. The evolution laws of mechanical and frost resistance properties of the mixture were investigated by unconfined compressive strength (UCS), indirect tensile strength (ITS), freeze-thaw (FT), and ultrasonic detection tests. Then, the strength formation mechanisms were revealed by microscopic characterization technology. The mathematical models between UCS-ITS, UCS-ultrasonic amplitude, FT cycles-UCS damage, and frost resistance coefficient-relative dynamic elastic modulus Er were established. The results show that cement content and curing age exhibited a positive effect on the mechanical strength and frost resistance of the mixture. When the replacement rate of SS was 60%, the mechanical strength and frost resistance were preferable. The R2 of the strength relationship models constructed was greater than 0.9, indicating high fitting accuracy. With the extension of the curing age, the cementitious products such as C-S-H (hydrated calcium silicate) and AFt (ettringite) developed entirely, and they were interlocked and cemented with each other, resulting in the micro-morphology developed from the three-dimensional network structure to the dense system. The macroscopic behavior incarnated that the mechanical strength and frost resistance of the mixture were significantly enhanced.

10.
Micromachines (Basel) ; 14(7)2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37512661

RESUMO

In advanced packaging technology, the micro bump has become an important means of chip stacking and wafer interconnection. The reliability of micro bumps, which plays an important role in mechanical support, electrical connection, signal transmission and heat dissipation, determines the quality of chip packaging. Surface morphological defects are one of the main factors affecting the reliability of micro bumps, which are closely related to materials and bonding process parameters. In this paper, the electrodeposition process of preparing gold bumps is simulated at the atomic scale using the Kinetic Monte Carlo method. The differences in surface morphology and roughness of the plated layer are studied from a microscopic perspective under different deposition parameters. The results show that the gold micro bumps prepared by electrodeposition have better surface quality under conditions of lower deposition voltage, lower ion concentration and higher plating temperature, which can provide significant guidance for engineering applications.

11.
J Colloid Interface Sci ; 645: 493-501, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37159991

RESUMO

Improving the performance of proton exchange membranes (PEMs) through the synthesis of sulfonated polymers with elaborate molecular structures has received extensive approval. However, the tedious synthetic process and consequently high costs restrain their possible substitution for Nafion, a classic PEM material. Herein, a series of semi-crystalline sulfonated poly(ether ketone)s with fluorene-based units were prepared via direct copolymerization of commercially available monomers and followed post-sulfonation, namely SPEK-FD-x, where × represents the molar ratio of the fluorene-containing monomer to the employed bisphenol monomers. The entire synthetic pathway was facile without involving hardly accessible materials. Subsequently, various properties of SPEK-FD-x membranes were investigated and further compared with Nafion 117. Due to the formation of the well-defined hydrophilic-hydrophobic microphase separation morphology and the reinforcement of the PEK crystalline regions, the SPEK-FD-x membranes exhibited outstanding proton conductivity, resistance for methanol permeation, as well as dimensional, thermal, oxidative, and mechanical stability. Among them, the overall behavior of the SPEK-FD-25 membrane was comparable to or even greater than that of Nafion 117, most importantly, it also performed decently in both H2/air fuel cells and direct methanol fuel cells. Therefore, with the straightforward synthesis and superior performance, the SPEK-FD-x membranes may serve as a promising alternative to Nafion.

12.
Environ Sci Pollut Res Int ; 30(43): 96660-96677, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37578582

RESUMO

To solve the disposal problems of carbide slag (CS), soda residue (SR), and red mud (RM) solid wastes, a new type of cemented paste backfill (CPB) was prepared with CS, SR, and RM solid wastes. The mixing proportion for the CPB was optimized by combining the Box‒Behnken design (BBD) response surface method and the satisfaction function method. The strength formation mechanism for the CPB was analyzed with physical and mechanical property tests, X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), etc. The safety of the CPB was evaluated with heavy metal leaching testing. The results showed that the 28-day unconfined compressive strength (UCS) of CPB first increased and then decreased with increasing CS/RM (0.2 ~ 0.6) and SR/RM (0.2 ~ 0.6); the optimum mixing ratios were CS/RM = 0.45 and SR/RM = 0.37, and the solid mass concentration was 64.75%; dense calcium silicate (aluminum) hydrate (C-S-H/C-A-S-H) bound to the solid particles of red mud and filled pores to provide early strength for the CPB, laminar interwoven Friedel's salt (Fs), ettringite and portlandite hydration products provided late strength for the CPB; and the leaching concentrations of five heavy metals (Fe, Mn, Cu, Zn, and Cr) in the solidified CPB were greatly reduced and far below the leaching limits specified in China's Quality Standard for Groundwater (GB/T 14848-2017).


Assuntos
Metais Pesados , Resíduos Sólidos , Metais Pesados/análise , Clima , Alumínio , Difração de Raios X
13.
ACS Appl Mater Interfaces ; 15(20): 24517-24527, 2023 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-37186810

RESUMO

Branched sulfonated polymers present considerable potential for application as proton exchange membranes, yet investigation of branched polymers containing sulfonated branched centers remains to be advanced. Herein, we report a series of polymers with ultradensely sulfonated branched centers, namely, B-x-SPAEKS, where x represents the degree of branching. In comparison with the analogous polymers bearing sulfonated branched arms, B-x-SPAEKS showed a reduced water affinity, resulting in less swelling and lower proton conductivity. The water uptake, swelling ratio (in-plane), and proton conductivity of B-10-SPAEKS at 80 °C were 52.2%, 57.7%, and 23.6% lower than their counterparts, respectively. However, further analysis revealed that B-x-SPAEKS featured significantly better proton conduction under the same water content due to the formation of larger hydrophilic clusters (∼10 nm) that promoted efficient proton transportation. B-12.5-SPAEKS exhibited a proton conductivity of 138.8 mS cm-1 and a swelling ratio (in-plane) of only 11.6% at 80 °C, both of which were superior to Nafion 117. In addition, a decent single-cell performance of B-12.5-SPAEKS was also achieved. Consequently, the decoration of sulfonic acid groups on the branched centers represents a very promising strategy, enabling outstanding proton conductivity and dimensional stability simultaneously even with low water content.

14.
Materials (Basel) ; 15(2)2022 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-35057303

RESUMO

To study the influence of nano-additives on the friction-wear characteristics of friction materials, the nano-sized silicon carbide particles which have excellent chemical and physical properties are considered to add in composite to form the modified friction material. The influence of the silicon carbide nanoparticles (SCN) on the friction-wear characteristics of copper-based friction materials (CBFM) is investigated via the SAE#2 (made in Hangzhou, China) clutch bench test with the applied pressure, rotating speed, and automatic transmission fluid (ATF) temperature taken into account. Moreover, the variations of friction torque and temperature are considered to evaluate the friction performance, and the variable coefficient is employed to describe the friction stability. The wear characteristics of friction materials are investigated by the disc changes in thickness and micro-morphology. The results show that the CBFM with SCN can provide a higher friction torque, which increased by 30% to 50% compared with CBFM. The variable coefficient of CBFM with SCN changes from 674 to 52 with the rotating speed raised from 600 rpm to 3000 rpm, which shows that the friction stability is relatively worse. Furthermore, the micromorphology shows that the CBFM with SCN has lower porosity and surface roughness, which increases the microscopic contact area and the coefficient of friction (COF). Simultaneously, the reduction in porosity also leads to a decrease in the cooling quality, bringing about a rapid temperature rise. Thus, the wear amount of CBFM with SCN increases significantly, especially for the friction disc in the axial middle position.

15.
Materials (Basel) ; 15(8)2022 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-35454484

RESUMO

The hydration process and compressive strength and flexural strength development of sulphate-resistant Portland cement (SRPC) curing at 20 °C, 40 °C, 50 °C, and 60 °C were studied. In addition, MIP, XRD, SEM, and a thermodynamic simulation (using Gibbs Energy Minimization Software (GEMS)) were used to study the pore structure, the types, contents, and transformations of hydration products, and the changes in the internal micro-morphology. The results indicate that, compared with normal-temperature curing (20 °C), the early compressive strength (1, 3, and 7 d) of SRPC cured at 40~60 °C increased by 10.1~57.4%, and the flexural strength increased by 1.8~21.3%. However, high-temperature curing was unfavorable for the development of compressive strength and flexural strength in the later period (28~90 d), as they were reduced by 1.5~14.6% and 1.1~25.5%, respectively. With the increase in the curing temperature and curing age, the internal pores of the SRPC changed from small pores to large pores, and the number of harmful pores (>50 nm) increased significantly. In addition, the pore structure was further coarsened after curing at 60 °C for 90 d, and the number of multiple harmful pores (>200 nm) increased by 17.9%. High-temperature curing had no effect on the types of hydration products of the SRPC but accelerated the formation rate of hydration products. The production of the hydration products C-S-H increased by 13.5%, 18.6%, and 22.8% after curing at 40, 50, and 60 °C for 3 d, respectively. The stability of ettringite (AFt) reduced under high-temperature curing, and its diffraction peak was not observed in the XRD patterns. When the curing temperature was higher than 50 °C, AFt began to transform into monosulfate, which consumed more tricalcium aluminate hydrate and inhibited the formation of "delayed ettringite". Under high-temperature curing, the compactness of the internal microstructure of the SRPC decreased, and the distribution of hydration products was not uniform, which affected the growth in its strength during the later period.

16.
Materials (Basel) ; 15(22)2022 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-36431380

RESUMO

As a common building insulation material, foamed concrete has been widely used in engineering practice. However, the contradiction between compressive strength and thermal conductivity has become the main problem limiting the development and application of foamed concrete. Therefore, high-performance foam concrete (HPFC) with high compressive strength and low thermal conductivity was prepared by using graphene oxide (GO), fly ash, and polypropylene (PP) fiber as the main admixtures, and taking compressive strength, thermal conductivity, and microstructure as the main indices. Scanning electron microscopy, X-ray diffraction (XRD), and thermogravimetry-differential scanning calorimetry (TG-DSC) were employed to examine the mechanisms of HPFC. The results showed that when the content of fly ash was 25-35 wt%, PP fiber was 0.2-0.4 wt%, and GO was 0.02-0.03 wt%, the FC's compressive strength increased by up to 38%, and its thermal conductivity reduced by up to 3.4%. Fly ash improved the FC's performance mainly through filling, pozzolanic activity, and slurry fluidity. PP fiber enhanced the performance of FC mainly through bridging cracks and skeletal effects. The addition of GO had no significant impact on the type, quantity, or hydration reaction rate of the hydration products in these cement-based materials, and mainly improved the FC's microstructural compactness through template action and crack resistance, thereby improving its performance.

17.
J Histotechnol ; 45(2): 85-91, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-34787535

RESUMO

Cryopreserving tissues for histology requires the use of coolants to buffer the sample from liquid nitrogen (LN2) and to control the rate of temperature decline. Several coolants sharing similar physical characteristics are available on the market; however, commonly used coolants are variably flammable and/or toxic and pose risks to personnel and facilities. The purpose of this study was to compare the performance of three commercially available coolants: hexane, 2-methylbutane (2 M), and 1-methoxyheptafluoropropane (N7000). Fresh mouse tissues were frozen by each method, for their ability to preserve microscopic architecture and to protect RNA from degradation were evaluated and compared to tissue characteristics obtained by direct immersion in LN2. Our results show that for most tissues, the N7000 freezing coolant provides equal or improved preservation of microscopic architecture. While snap-freezing tissues in LN2 provides superior RNA protection, no significant differences in RNA quality were seen between tissues frozen in hexane, 2 M, and N7000.


Assuntos
Criopreservação , Hexanos , Animais , Criopreservação/métodos , Congelamento , Camundongos , RNA , Temperatura
18.
Materials (Basel) ; 14(8)2021 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-33923633

RESUMO

The type and fineness of a filler significantly affect the performance of an asphalt mixture. There is a lack of specific research on the effects of filler fineness and dust from aggregates on the properties of epoxy asphalt (EA) mixtures. The effects of aggregate dust and mineral powder on the properties of an EA mixture were evaluated. These filler were tested to determine their fineness, specific surface area and mineral composition. The effects of these fillers on the EA mastic sample and mixture were evaluated. The morphology of the EA mastic samples was analyzed using scanning electron microscopy (SEM). The effects of the fillers on the Marshall stability, tensile strength and fatigue performance of the EA mixture were evaluated. The dust from the aggregates exhibited an even particle size distribution, and its average particle size was approximately 20% of that of the mineral powder. The SEM microanalysis showed that the EA mastic sample containing relatively fine dust formed a tight and dense interfacial bonding structure with the aggregate. The EA mixture sample containing filler composed of dust from aggregate had a significantly higher strength and longer fatigue life than that of the EA sample containing filler composed of mineral powder.

19.
Sci Justice ; 61(4): 435-442, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34172133

RESUMO

With continuous innovations in laser printing technology, the number of cases of falsification using laser printers is increasing annually. Difficulties in identifying printing alternations, especially laser-printed alternations by the same printer are increasing. Effectively, repeated printing on the same page by the same printer means the original toner on the document was fused repeatedly. Thus, this study mainly investigates the effects of second fusing on the microscopic morphology of toner to examine whether documents have been tampered with. To detect the influence of fusing on the microscopic morphology of toner, 170 documents printed by 17 different models of laser printers from 5 brands were studied. It was found that, according to microscopic observations, the micrographs of toner may become brighter, darker or both with repetition of the fusing process. By calculating the average gray value of the micrographs of toner, it was found that, in some laser printers, the gray value of the thermoplastic accumulation area will increase after a second fusing, and the gray value of the toner particle dispersion area will decrease. In conclusion, by comparing the micrographs of toner from suspicious and reliable contents on the same page or in the same document, together with the measurement and analysis of average gray values, it is possible to examine the once- and twice-fused document contents, and further determine whether the document has been altered.


Assuntos
Lasers , Humanos
20.
Environ Sci Pollut Res Int ; 28(1): 564-573, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32815015

RESUMO

This study aims to reveal the evolutionary process of particles during the diesel exhaust transport process and to further understand the effects of diesel exhaust transport distance (DET) on a particulate microstructure. Specifically, the micromorphological, particle size distribution, and aggregate characteristics of particles as well as the variation of the structural characteristics of elementary carbon particles (ECPs) as DET changed were examined using an engine exhaust particle size spectrometer, a high-resolution transmission electron microscopy system, and a small-angle X-ray scattering system. The results show the following: As DET increased, the chains gradually lengthened, the extent of accumulation and stacking increased, and a number of clusters gradually rose. The average particle diameter increased from 23.1 nm at 0 m to 92.7 nm at 3 m. In addition, as DET increased, the number of accumulation-mode particles, the number of folded, curved carbon layers in the inner core of carbon particles, and the disorderliness of carbon layers in the outer shell of carbon particles all increased. Moreover, the boundary between the inner core and the outer shell became increasingly obscure. As DET increased, there was a gradual decrease in the difference in electron density between particles, and the fractal dimensionality of the distribution, average cross-sectional size, radius of gyration, and axial length of pores were, respectively, 33.3%, 40%, 38.2%, and 50.3% less at 3 m than at 0 m. Besides that, the number of small (< 3 nm) pores gradually increased, and the number of large (> 10 nm) pores gradually decreased. Overall, as DET increased, pore size and number decreased. There was a gradual increase in the number of folded and curved carbon layers in the inner core of ECPs and an increase in the disorderliness of carbon layers in their outer shell as DET increased. Furthermore, the boundary between the inner core and the outer shell became increasingly obscure as DET increased. The crystallite size of ECPs decreased from 1.365 nm at 0 m to 1.098 nm at 3 m. This suggests that the number of continuously arranged carbon atoms decreased, the arrangement of carbon atoms was more disorderly, and the degree of graphitization decreased. As DET increased, there was a gradual increase in the interlayer spacing and curvature of ECPs. This suggests that increasing DET led to a more disorderly distribution of electron orbitals inside the carbon layers, less electron resonance stability in the carbon layers, greater oxidative activity of ECPs, and greater inherent oxidative capacity of particles.


Assuntos
Material Particulado , Emissões de Veículos , Estudos Transversais , Poeira , Tamanho da Partícula , Emissões de Veículos/análise
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