2022 Vol. 55 No. 4
2022, 54(4): 1-6.
DOI: 10.6054/j.jscnun.2022051
Abstract：
Phase stability and frequency-dependent ferroelectric and dielectric properties of epitaxial Ba0.6Sr0.4TiO3 thin films under different misfit strains were investigated using a modified Landau-Devonshire phenomenological theory combined with Landau-Khalatnikov equation. The phase diagram analysis indicates that ferroelectric tetragonal (c), orthogonal (aa) and paraelectric phases are stable at room temperature and all phase transitions are of second order. The compressive misfit strain increases out-of-plane remnant polarization (Pr) and coercive field (Ec) in c phase while the tensile misfit strain augments in-plane Pr and Ec in aa phase at an electric field frequency of 0.1 kHz. Moreover, it is found that both polarization and coercive field increase with increasing frequency while the dielectric constant decreases rapidly first and then slowly. The maximum tunability decreases and the corresponding misfit strain gradually approaches zero, which is attributed to the enhancement of phase transition temperature (ΔTc). The further calculation results reveal that the shift of misfit strain, decrease in tunability and ΔTc are 0.017%, 10.6% and 7.3 ℃ respectively in the out-of-plane case, which are comparable to 0.019%, 9.7% and 7.7 ℃ respectively for the in-plane case.
Phase stability and frequency-dependent ferroelectric and dielectric properties of epitaxial Ba0.6Sr0.4TiO3 thin films under different misfit strains were investigated using a modified Landau-Devonshire phenomenological theory combined with Landau-Khalatnikov equation. The phase diagram analysis indicates that ferroelectric tetragonal (c), orthogonal (aa) and paraelectric phases are stable at room temperature and all phase transitions are of second order. The compressive misfit strain increases out-of-plane remnant polarization (Pr) and coercive field (Ec) in c phase while the tensile misfit strain augments in-plane Pr and Ec in aa phase at an electric field frequency of 0.1 kHz. Moreover, it is found that both polarization and coercive field increase with increasing frequency while the dielectric constant decreases rapidly first and then slowly. The maximum tunability decreases and the corresponding misfit strain gradually approaches zero, which is attributed to the enhancement of phase transition temperature (ΔTc). The further calculation results reveal that the shift of misfit strain, decrease in tunability and ΔTc are 0.017%, 10.6% and 7.3 ℃ respectively in the out-of-plane case, which are comparable to 0.019%, 9.7% and 7.7 ℃ respectively for the in-plane case.
2022, 54(4): 7-17.
DOI: 10.6054/j.jscnun.2022052
Abstract：
In order to evaluate the impact of various behaviors of drivers operating mobile phones on driving safety, 19 drivers were organized to wear an eye tracker to carry out indoor simulation driving test, and the fixation data of drivers during normal driving, hands-free call and voice message in two typical traffic conditions of free flow and crowded flow of urban expressway were collected respectively. The driver's visual field plane is divided and classified into six visual interest areas with the hierarchical clustering method combined with mechanical division. Using descriptive statistics and variance analysis, a set of sensitive indexes (information entropy of fixation area, fixation duration, vertical fixation deviation and coefficient of variation of pupil area) was established to measure the characteristics of fixation behavior. Finally, the entropy weight method was used to construct the weight system of four indicators and propose the concept of distraction load index, and the TOPSIS method was introduced to verify the evaluation effect of distraction load index on the degree of distraction. The results show that most drivers are in the cognitive distraction state during hands-free call operation and in the visual distraction state during voice message operation. Compared with normal driving, except that there is little impact on distraction load during hands-free call operation in the free flow scenario, other mobile phone operations have a significant impact on the drivers' fixation behavior, resulting in a general increase in distraction load index. In addition, in the crowded flow scenario, the distraction load increases sharply when performing voice message operation, and the driving risk is much higher than that of hands-free call.
In order to evaluate the impact of various behaviors of drivers operating mobile phones on driving safety, 19 drivers were organized to wear an eye tracker to carry out indoor simulation driving test, and the fixation data of drivers during normal driving, hands-free call and voice message in two typical traffic conditions of free flow and crowded flow of urban expressway were collected respectively. The driver's visual field plane is divided and classified into six visual interest areas with the hierarchical clustering method combined with mechanical division. Using descriptive statistics and variance analysis, a set of sensitive indexes (information entropy of fixation area, fixation duration, vertical fixation deviation and coefficient of variation of pupil area) was established to measure the characteristics of fixation behavior. Finally, the entropy weight method was used to construct the weight system of four indicators and propose the concept of distraction load index, and the TOPSIS method was introduced to verify the evaluation effect of distraction load index on the degree of distraction. The results show that most drivers are in the cognitive distraction state during hands-free call operation and in the visual distraction state during voice message operation. Compared with normal driving, except that there is little impact on distraction load during hands-free call operation in the free flow scenario, other mobile phone operations have a significant impact on the drivers' fixation behavior, resulting in a general increase in distraction load index. In addition, in the crowded flow scenario, the distraction load increases sharply when performing voice message operation, and the driving risk is much higher than that of hands-free call.
Abstract：
WO3/graphene nanocomposites were successfully prepared with the simple low-temperature chemical synthesis method and they showed excellent photo-activated toluene gas-sensing properties at room temperature. The results showed that the addition of graphene would reduce the size of WO3 lamella to about 300 nm and assemble it into a spherical structure. Graphene and WO3 would form a chemical bond in the composite, effectively reducing the concentration of oxygen vacancies in WO3. The photo-activated gas-sensing response of WO3/graphene composite to 100 mL/m3 toluene under blue light was 3.3 times higher than that of pure WO3. The material may have a good prospect for application in the explosive, flammable and toxic environment.
WO3/graphene nanocomposites were successfully prepared with the simple low-temperature chemical synthesis method and they showed excellent photo-activated toluene gas-sensing properties at room temperature. The results showed that the addition of graphene would reduce the size of WO3 lamella to about 300 nm and assemble it into a spherical structure. Graphene and WO3 would form a chemical bond in the composite, effectively reducing the concentration of oxygen vacancies in WO3. The photo-activated gas-sensing response of WO3/graphene composite to 100 mL/m3 toluene under blue light was 3.3 times higher than that of pure WO3. The material may have a good prospect for application in the explosive, flammable and toxic environment.
2022, 54(4): 25-31.
DOI: 10.6054/j.jscnun.2022054
Abstract：
In order to explore the adsorption mechanism of Mn(Ⅱ) on illite surfaces, the density functional theory (DFT) was used to simulate the adsorption of Mn(Ⅱ) on the (001) and (010) surfaces. The active site, adsorption configuration, charge and state density were studied, and the following conclusions were obtained. On the (001) surface, Mn(Ⅱ) was adsorbed preferentially on the hole of silicon oxygen ring and formed a covalent bond with the active oxygen OS1, with an adsorption energy of -262.55 kJ/mol. On the (010) surface, Mn(Ⅱ) formed 1 to 3 covalent bonds with OS from hydroxyl groups, and the adsorption energy increased with the increase of covalent bonds. The most stable adsorption configuration was Mn(Ⅱ) adsorbed on the holes between three ≡Al—OH groups, and the adsorption energy was -533.62 kJ/mol. There were covalent bond interactions and electrostatic interactions between Mn(Ⅱ) and the (001) and (010) surfaces. The adsorption energy of Mn(Ⅱ) on (001) surface was less than that on the (010) surface. The adsorption of Mn(Ⅱ) on the (001) surface was mainly electrostatic interaction and that on the (010) surface was mainly covalent interaction. The formation of the surface covalent bond between Mn(Ⅱ) and illite was mainly due to the interaction between the 4s orbital of Mn and the 2p orbital of OS. The results can provide a theoretical basis for the development of clay adsorption materials or the purification of contaminated soil.
In order to explore the adsorption mechanism of Mn(Ⅱ) on illite surfaces, the density functional theory (DFT) was used to simulate the adsorption of Mn(Ⅱ) on the (001) and (010) surfaces. The active site, adsorption configuration, charge and state density were studied, and the following conclusions were obtained. On the (001) surface, Mn(Ⅱ) was adsorbed preferentially on the hole of silicon oxygen ring and formed a covalent bond with the active oxygen OS1, with an adsorption energy of -262.55 kJ/mol. On the (010) surface, Mn(Ⅱ) formed 1 to 3 covalent bonds with OS from hydroxyl groups, and the adsorption energy increased with the increase of covalent bonds. The most stable adsorption configuration was Mn(Ⅱ) adsorbed on the holes between three ≡Al—OH groups, and the adsorption energy was -533.62 kJ/mol. There were covalent bond interactions and electrostatic interactions between Mn(Ⅱ) and the (001) and (010) surfaces. The adsorption energy of Mn(Ⅱ) on (001) surface was less than that on the (010) surface. The adsorption of Mn(Ⅱ) on the (001) surface was mainly electrostatic interaction and that on the (010) surface was mainly covalent interaction. The formation of the surface covalent bond between Mn(Ⅱ) and illite was mainly due to the interaction between the 4s orbital of Mn and the 2p orbital of OS. The results can provide a theoretical basis for the development of clay adsorption materials or the purification of contaminated soil.
2022, 54(4): 32-39.
DOI: 10.6054/j.jscnun.2022055
Abstract：
A carbazole derivative (HCTC) containing siloxy groups was synthesized using 4-hydroxycarbazole as the raw material. The structure was characterized with 1H NMR and MS, and the F- detection performance of the probe was studied. The results showed that HCTC could take advantage of the nucleophilicity of F- to specifically attack the silicon-oxygen bond, showing the characteristics of a chemically reactive fluorescent probe towards F-. Fluorescence test results showed that when F- was added, a new fluorescence emission peak appeared in the probe solution at the wavelength of 433 nm, accompanied by a slight red shift, while the addition of other common anions could not cause fluorescence enhancement. In addition, the detection limit of F- by HCTC was relatively low (0.21 μmol/L). Finally, the HCTC probe was prepared into a fluorescent test paper, which could detect F- in an aqueous solution containing a small amount of acetonitrile. HCTC can be a fluorescence-enhanced probe with high selectivity and sensitivity.
A carbazole derivative (HCTC) containing siloxy groups was synthesized using 4-hydroxycarbazole as the raw material. The structure was characterized with 1H NMR and MS, and the F- detection performance of the probe was studied. The results showed that HCTC could take advantage of the nucleophilicity of F- to specifically attack the silicon-oxygen bond, showing the characteristics of a chemically reactive fluorescent probe towards F-. Fluorescence test results showed that when F- was added, a new fluorescence emission peak appeared in the probe solution at the wavelength of 433 nm, accompanied by a slight red shift, while the addition of other common anions could not cause fluorescence enhancement. In addition, the detection limit of F- by HCTC was relatively low (0.21 μmol/L). Finally, the HCTC probe was prepared into a fluorescent test paper, which could detect F- in an aqueous solution containing a small amount of acetonitrile. HCTC can be a fluorescence-enhanced probe with high selectivity and sensitivity.
2022, 54(4): 40-47.
DOI: 10.6054/j.jscnun.2022056
Abstract：
TiO2-rGO composites were synthesized with the liquid phase deposition and calcination method. The as-prepared photocatalysts were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), specific surface and porosity analyzer (BET) and ultraviolet-visible diffuse reflectance spectrophotometer (UV-Vis DRS). The degradation performance of ozonation photocata-lyzed by TiO2-rGO was investigated using bisphenol A (BPA) as the model pollutant. The reaction mechanism was further explored through the active species trapping experiment. The results showed that anatase TiO2 nanoparticles about 20 nm in diameter had been successfully anchored on the surface of graphene. The sample obtained when 0.02 g graphite oxide was added in precursor solution exhibited the highest activity and BPA was completely mineralized within 45 min. The catalytic activity of TiO2-rGO still showed efficient performance after recycling for five consecutive runs. The catalytic activity of TiO2-rGO was enhanced owing to the improved separation efficiency of photo-generated charges through the introduction of rGO, which benefited the synergistic degradation of photocata-lysis and ozonation. In the reaction process, holes (h+) and hydroxyl radical (·OH)were the main active species and ·OH played a dominant role in BPA degradation.
TiO2-rGO composites were synthesized with the liquid phase deposition and calcination method. The as-prepared photocatalysts were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), specific surface and porosity analyzer (BET) and ultraviolet-visible diffuse reflectance spectrophotometer (UV-Vis DRS). The degradation performance of ozonation photocata-lyzed by TiO2-rGO was investigated using bisphenol A (BPA) as the model pollutant. The reaction mechanism was further explored through the active species trapping experiment. The results showed that anatase TiO2 nanoparticles about 20 nm in diameter had been successfully anchored on the surface of graphene. The sample obtained when 0.02 g graphite oxide was added in precursor solution exhibited the highest activity and BPA was completely mineralized within 45 min. The catalytic activity of TiO2-rGO still showed efficient performance after recycling for five consecutive runs. The catalytic activity of TiO2-rGO was enhanced owing to the improved separation efficiency of photo-generated charges through the introduction of rGO, which benefited the synergistic degradation of photocata-lysis and ozonation. In the reaction process, holes (h+) and hydroxyl radical (·OH)were the main active species and ·OH played a dominant role in BPA degradation.
2022, 54(4): 48-55.
DOI: 10.6054/j.jscnun.2022057
Abstract：
A serias of novel mesoporous carbon/silica composites (BC/SiO2) with abundant mesoporous structure were successfully prepared with the sol-gel self-assembly method, wherein triblock copolymer F127 was used as a template, tetraethoxysilane was used as an inorganic silicon precursor, and phenolic resin and triisopropyl borate were selected as C- and B- containing precursors. Meanwhile, the effect of the content of boron doped on the CO2 capture capacity of BC/SiO2 composites was investigated and the adsorption isotherms of CO2 were determined. The results were fitted and analyzed using three kinds of adsorption isotherms models (Langmuir, Freundlich and DSL models). These results demonstrated that the BC/SiO2 composites exhibited a spherical shape and had a high specific surface area and uniform pore distribution and a large amount of boron atoms was uniformly doped in the carbon framework of BC/SiO2 composite, which introduced the polar sites. The capability of capturing CO2 was not only related to the specific surface area of the composite material but also to the number of polar sites generated by doped boron. It was found that the adsorption CO2 molecules on BC/SiO2 composites presented two adsorption sites with different degrees and adsorption isotherms of CO2 were highly consistent with the DSL model.
A serias of novel mesoporous carbon/silica composites (BC/SiO2) with abundant mesoporous structure were successfully prepared with the sol-gel self-assembly method, wherein triblock copolymer F127 was used as a template, tetraethoxysilane was used as an inorganic silicon precursor, and phenolic resin and triisopropyl borate were selected as C- and B- containing precursors. Meanwhile, the effect of the content of boron doped on the CO2 capture capacity of BC/SiO2 composites was investigated and the adsorption isotherms of CO2 were determined. The results were fitted and analyzed using three kinds of adsorption isotherms models (Langmuir, Freundlich and DSL models). These results demonstrated that the BC/SiO2 composites exhibited a spherical shape and had a high specific surface area and uniform pore distribution and a large amount of boron atoms was uniformly doped in the carbon framework of BC/SiO2 composite, which introduced the polar sites. The capability of capturing CO2 was not only related to the specific surface area of the composite material but also to the number of polar sites generated by doped boron. It was found that the adsorption CO2 molecules on BC/SiO2 composites presented two adsorption sites with different degrees and adsorption isotherms of CO2 were highly consistent with the DSL model.
2022, 54(4): 56-64.
DOI: 10.6054/j.jscnun.2022058
Abstract：
Nano zero valent iron nanoparticles (GS-nZVI) were green-synthesized with pomegranate peel extract as the reducing agent and stabilizer. The physical and chemical properties of GS-nZVI product were characterized with scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscop (FTIR), X-ray photoelectron spectroscop (XPS) and Thermo-Gravimetric Analysis (TGA). The particle size and surface Zeta potential of the products were measured with the laser-scattering Zetasizer instrument. Based on the basic principle of chemical equilibrium, the effects of synthesis conditions such as reaction time, iron salt concentration and polyphenol concentration on the particle size and yield were discussed and the possible mechanism was proposed. The results showed that GS-nZVI synthesized from pomegranate peel extract had an amorphous structure and polyphenols in the extract not only reduced the ferritic salt (Fe2+) to Fe0 but also coated on the surface of nanoparticles as a stabilizer to improve the dispersion of the samples. The results proved that 120 min reaction time, 0.05 mol/L Fe2+ and 15 mg/mL polyphenol was the best preparation condition of GS-nZVI with the highest yield and the smallest particle size, and the mean particle size was 213 nm.
Nano zero valent iron nanoparticles (GS-nZVI) were green-synthesized with pomegranate peel extract as the reducing agent and stabilizer. The physical and chemical properties of GS-nZVI product were characterized with scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscop (FTIR), X-ray photoelectron spectroscop (XPS) and Thermo-Gravimetric Analysis (TGA). The particle size and surface Zeta potential of the products were measured with the laser-scattering Zetasizer instrument. Based on the basic principle of chemical equilibrium, the effects of synthesis conditions such as reaction time, iron salt concentration and polyphenol concentration on the particle size and yield were discussed and the possible mechanism was proposed. The results showed that GS-nZVI synthesized from pomegranate peel extract had an amorphous structure and polyphenols in the extract not only reduced the ferritic salt (Fe2+) to Fe0 but also coated on the surface of nanoparticles as a stabilizer to improve the dispersion of the samples. The results proved that 120 min reaction time, 0.05 mol/L Fe2+ and 15 mg/mL polyphenol was the best preparation condition of GS-nZVI with the highest yield and the smallest particle size, and the mean particle size was 213 nm.
2022, 54(4): 65-73.
DOI: 10.6054/j.jscnun.2022059
Abstract：
In order to investigate the effect of replacing fish meal with low-phenol cottonseed meal (LCSM) on flesh quality, antioxidant capacity and related gene expression of golden pompano, 4 groups of LCSM-added feeds were prepared to replace 0% (LCSM0), 20% (LCSM20), 40% (LCSM40) and 60% (LCSM60) fish meal protein and golden pompano of 28.42±0.02 g were fed for 6 weeks. The results are as follows. First, there was no statistically significant difference in flesh hardness, elasticity, cohesion, glue viscosity and recovery between LCSM20 group and LCSM0 group (P>0.05), and the adhesion and chewiness of LCSM20 group decreased significantly (P < 0.05); the cohesion of LCSM40 group and LCSM60 group increased significantly (P < 0.05), and the other texture indexes decreased significantly (P < 0.05). Second, there was statistically significant difference in pH and cooking loss rate of LCSM20, LCSM40 and LCSM60 group compared with LCSM0 group (P < 0.05), and there was no statistically significant difference in flesh drip loss rate (P>0.05). Third, there was no statistically significant difference in mass fraction of collagen of LCSM20 and LCSM40 group compared with LCSM0 group(P>0.05). Fourth, the content of malondialdehyde (MDA) and the activity of glutathione peroxidase (GSH-Px) in LCSM20 group showed no change compared with LCSM0 group (P>0.05), but the SOD activity was down-regulated in LCSM20 group (P < 0.05). There was no statistically significant difference in MDA content between LCSM40 and LCSM60 group compared with LCSM0 group (P>0.05). The SOD activity and GSH-Px content were deceased in LCSM40 and LCSM60 group (P < 0.05). Fifth, there was no statistically significant difference in the transcription level of flesh quality-related genes (Decorin, MSTN, MyoG and CatL) in LCSM20 group compared with LCSM0 group (P>0.05). The COL1α1 and CatB gene transcription levels were significantly up-regulated (P < 0.05). The transcription levels of MSTN and COL1α1 genes in the LCSM40 and LCSM60 groups were significantly up-regulated compared with LCSM0 group (P < 0.05). In addition, the transcription levels of Decorin, MyoG, CatB and CatL genes in the LCSM40 group were no statistically significantly different from those in LCSM0 group (P>0.05); the Decorin gene transcription level in the LCSM60 group was significantly down-regulated compared with LCSM0 group (P < 0.05), the MyoG gene transcription level was no statistically significantly different from that in LCSM0 group, and CatB and CatL gene transcription levels were significantly up-regulated compared with LCSM0 group (P < 0.05). In summary, with the effect on flesh quality, antioxidant capacity and related gene expression as evaluation indicators, the optimal amount of LCSM addition in the golden pompano feed is 20%.
In order to investigate the effect of replacing fish meal with low-phenol cottonseed meal (LCSM) on flesh quality, antioxidant capacity and related gene expression of golden pompano, 4 groups of LCSM-added feeds were prepared to replace 0% (LCSM0), 20% (LCSM20), 40% (LCSM40) and 60% (LCSM60) fish meal protein and golden pompano of 28.42±0.02 g were fed for 6 weeks. The results are as follows. First, there was no statistically significant difference in flesh hardness, elasticity, cohesion, glue viscosity and recovery between LCSM20 group and LCSM0 group (P>0.05), and the adhesion and chewiness of LCSM20 group decreased significantly (P < 0.05); the cohesion of LCSM40 group and LCSM60 group increased significantly (P < 0.05), and the other texture indexes decreased significantly (P < 0.05). Second, there was statistically significant difference in pH and cooking loss rate of LCSM20, LCSM40 and LCSM60 group compared with LCSM0 group (P < 0.05), and there was no statistically significant difference in flesh drip loss rate (P>0.05). Third, there was no statistically significant difference in mass fraction of collagen of LCSM20 and LCSM40 group compared with LCSM0 group(P>0.05). Fourth, the content of malondialdehyde (MDA) and the activity of glutathione peroxidase (GSH-Px) in LCSM20 group showed no change compared with LCSM0 group (P>0.05), but the SOD activity was down-regulated in LCSM20 group (P < 0.05). There was no statistically significant difference in MDA content between LCSM40 and LCSM60 group compared with LCSM0 group (P>0.05). The SOD activity and GSH-Px content were deceased in LCSM40 and LCSM60 group (P < 0.05). Fifth, there was no statistically significant difference in the transcription level of flesh quality-related genes (Decorin, MSTN, MyoG and CatL) in LCSM20 group compared with LCSM0 group (P>0.05). The COL1α1 and CatB gene transcription levels were significantly up-regulated (P < 0.05). The transcription levels of MSTN and COL1α1 genes in the LCSM40 and LCSM60 groups were significantly up-regulated compared with LCSM0 group (P < 0.05). In addition, the transcription levels of Decorin, MyoG, CatB and CatL genes in the LCSM40 group were no statistically significantly different from those in LCSM0 group (P>0.05); the Decorin gene transcription level in the LCSM60 group was significantly down-regulated compared with LCSM0 group (P < 0.05), the MyoG gene transcription level was no statistically significantly different from that in LCSM0 group, and CatB and CatL gene transcription levels were significantly up-regulated compared with LCSM0 group (P < 0.05). In summary, with the effect on flesh quality, antioxidant capacity and related gene expression as evaluation indicators, the optimal amount of LCSM addition in the golden pompano feed is 20%.
2022, 54(4): 74-81.
DOI: 10.6054/j.jscnun.2022060
Abstract：
Autophagy plays an important role in plant growth and development, but the relationship between autophagy and seed germination is not clear. Gene expression analysis, western blotting assay and seed germination rate assay were performed to explore the effect of autophagy on the germination of Arabidopsis thaliana seeds. The main experimental results are as follows. The expression of autophagy genes was significantly up-regulated and ATG8 proteins were gradually accumulated during seed germination, indicating that autophagy was activated in the process. Autophagy inhibitor 3-methyladenine (3-MA) could significantly inhibit seed germination of wild-type Arabidopsis thaliana, and in the normal condition, autophagy mutants had a slower seed germination rate than wild-type Arabidopsis thaliana, indicating that the autophagy pathway was involved in seed germination but not indispensable.
Autophagy plays an important role in plant growth and development, but the relationship between autophagy and seed germination is not clear. Gene expression analysis, western blotting assay and seed germination rate assay were performed to explore the effect of autophagy on the germination of Arabidopsis thaliana seeds. The main experimental results are as follows. The expression of autophagy genes was significantly up-regulated and ATG8 proteins were gradually accumulated during seed germination, indicating that autophagy was activated in the process. Autophagy inhibitor 3-methyladenine (3-MA) could significantly inhibit seed germination of wild-type Arabidopsis thaliana, and in the normal condition, autophagy mutants had a slower seed germination rate than wild-type Arabidopsis thaliana, indicating that the autophagy pathway was involved in seed germination but not indispensable.
2022, 54(4): 82-88.
DOI: 10.6054/j.jscnun.2022061
Abstract：
A link-to-link transition sampling method utilizing the historic data of link-to-link transition probability to obtain the multiple optimal routes between the given origin and destination in a road network (method of link-to-link transition probability for multiple optimal routes) was proposed to avoid the need of calculating the link travel times. Firstly, the link-to-link transition probabilities were calculated with travel data of time and region division. The impacts of traffic conditions were taken into account according to time division. And the problems of the large number of starting points and ending points and the insufficient data of specific point pairs in the road network were avoided by replacing the given starting point and ending point with the traffic zone. And multiple optimal routes were calculated with route sampling based on the link-to-link transition probability. The proposed method demonstrated the advantages of no need to calculate the link travel time, low requirement of data and easy implementation. A case study showed that the optimal routes obtained with the proposed method are much in accordance with the actual optimal routes. The size of traffic zones has minor impacts on the results, and the division of periods can effectively reflect the traffic conditions.
A link-to-link transition sampling method utilizing the historic data of link-to-link transition probability to obtain the multiple optimal routes between the given origin and destination in a road network (method of link-to-link transition probability for multiple optimal routes) was proposed to avoid the need of calculating the link travel times. Firstly, the link-to-link transition probabilities were calculated with travel data of time and region division. The impacts of traffic conditions were taken into account according to time division. And the problems of the large number of starting points and ending points and the insufficient data of specific point pairs in the road network were avoided by replacing the given starting point and ending point with the traffic zone. And multiple optimal routes were calculated with route sampling based on the link-to-link transition probability. The proposed method demonstrated the advantages of no need to calculate the link travel time, low requirement of data and easy implementation. A case study showed that the optimal routes obtained with the proposed method are much in accordance with the actual optimal routes. The size of traffic zones has minor impacts on the results, and the division of periods can effectively reflect the traffic conditions.
2022, 54(4): 89-100.
DOI: 10.6054/j.jscnun.2022062
Abstract：
The growth range, interannual biomass and biological carbon storage of Sonneratia apetala on Qi'ao Island from 1999 to 2019 was quantitatively calculated on the basis of multi-period remote sensing images and field-measured sample data to research the effect of fast carbon fixation of Sonneratia apetala and the reasons for the changes were analyzed. The biomass inversion model of the study area was obtained: B=75.906-6.144×SR-10.728×Variance, where P < 0.01, R2=0.700. As the results show, the area of Sonneratia apetala in 1999, 2003, 2009, 2013 and 2019 were 0, 29.520, 114.245, 140.280 and 332.399 hm2 respectively; the carbon stocks in 1999, 2003, 2009, 2013 and 2019 were 0, 4 872.74, 15 051.14, 25 892.55, 55 969.24 t respectively; the carbon sequestration rates from 1999 to 2003, 2003 to 2009, 2009 to 2013 and 2013 to 2019 are 3.66, 7.55, 19.48, 28.06 t/(hm2·a) respectively; and the carbon density per unit area of Sonneratia apetala has increased by 168.38 t/hm2 in the past 20 years. Compared with other mangrove species and subtropical broad-leaved forests at the same latitude, Sonneratia apetala is an ideal mangrove plant with faster carbon sequestration rate and greater carbon storage and can be used to restore bare land coasts.
The growth range, interannual biomass and biological carbon storage of Sonneratia apetala on Qi'ao Island from 1999 to 2019 was quantitatively calculated on the basis of multi-period remote sensing images and field-measured sample data to research the effect of fast carbon fixation of Sonneratia apetala and the reasons for the changes were analyzed. The biomass inversion model of the study area was obtained: B=75.906-6.144×SR-10.728×Variance, where P < 0.01, R2=0.700. As the results show, the area of Sonneratia apetala in 1999, 2003, 2009, 2013 and 2019 were 0, 29.520, 114.245, 140.280 and 332.399 hm2 respectively; the carbon stocks in 1999, 2003, 2009, 2013 and 2019 were 0, 4 872.74, 15 051.14, 25 892.55, 55 969.24 t respectively; the carbon sequestration rates from 1999 to 2003, 2003 to 2009, 2009 to 2013 and 2013 to 2019 are 3.66, 7.55, 19.48, 28.06 t/(hm2·a) respectively; and the carbon density per unit area of Sonneratia apetala has increased by 168.38 t/hm2 in the past 20 years. Compared with other mangrove species and subtropical broad-leaved forests at the same latitude, Sonneratia apetala is an ideal mangrove plant with faster carbon sequestration rate and greater carbon storage and can be used to restore bare land coasts.
2022, 54(4): 101-108.
DOI: 10.6054/j.jscnun.2022063
Abstract：
As the method for spectral estimation of Markov process makes use of nonnegativity-preserving step, the spectral estimator does not necessarily satisfy low-rank condition. Motivated by this, a low-rank spectral estimation algorithm (LRSEA) is proposed. First of all, the local Lipschitzian type error bound of the rank-constrained state transition matrix set is established, and an approximate projection matrix that satisfies the error bound inequality is given. Then, using the approximate projection matrix to modify the spectral estimation method, the LRSEA is proposed, and the statistical error bound for the proposed estimation method is provided. Numerical comparisons on the synthetic data with empirical estimator and spectral estimator show that the LRSEA has the lowest estimation error. Finally, the LRSEA together with k-means algorithm is used to analyze the dataset of Manhattan taxi trips.
As the method for spectral estimation of Markov process makes use of nonnegativity-preserving step, the spectral estimator does not necessarily satisfy low-rank condition. Motivated by this, a low-rank spectral estimation algorithm (LRSEA) is proposed. First of all, the local Lipschitzian type error bound of the rank-constrained state transition matrix set is established, and an approximate projection matrix that satisfies the error bound inequality is given. Then, using the approximate projection matrix to modify the spectral estimation method, the LRSEA is proposed, and the statistical error bound for the proposed estimation method is provided. Numerical comparisons on the synthetic data with empirical estimator and spectral estimator show that the LRSEA has the lowest estimation error. Finally, the LRSEA together with k-means algorithm is used to analyze the dataset of Manhattan taxi trips.
2022, 54(4): 109-112.
DOI: 10.6054/j.jscnun.2022064
Abstract：
The properties of the set of points where Elton's theorem does not hold are given. By constructing cylinder sets in symbolic space, it is proved that for a contractive IFS with probabilities and a continuous function g sa-tisfying that ∫Xg dν1≠∫Xg dν2, where ν1 and ν2 are any two different invariant measures of the IFS, the zero measure invariant set composed of points where Elton's theorem does not hold is either empty or carries full Hausdorff dimension and topological entropy.
The properties of the set of points where Elton's theorem does not hold are given. By constructing cylinder sets in symbolic space, it is proved that for a contractive IFS with probabilities and a continuous function g sa-tisfying that ∫Xg dν1≠∫Xg dν2, where ν1 and ν2 are any two different invariant measures of the IFS, the zero measure invariant set composed of points where Elton's theorem does not hold is either empty or carries full Hausdorff dimension and topological entropy.
2022, 54(4): 113-120.
DOI: 10.6054/j.jscnun.2022065
Abstract：
Normal EEG signals are susceptible to contamination by various EEG artifacts, resulting in low signal-to-noise ratios. In order to improve the signal-to-noise ratio of EEG signals, a metric-based few-shot learning method was used to detect EEG artifacts. A few-shot learning model named EEG Artifact Prototype Network (EAPNet) based on a prototype network was proposed to detect artifacts in EEG signals. The model was able to learn a nonlinear mapping from EEG features to the target space, calculate the distance of each class prototype representation and classify them according the distance. In addition, the EAPNet model required only a small number of examples of each new class to train the model to achieve accurate recognition of artifact signals. Artifact recognition experiments were conducted in the public EEG artifact dataset TUAR (TUH EEG Artifact Corpus). The EAPNet model is compared with 2 deep learning models (EEGNet, Fully Connected Neural Network (FNN)) and 7 machine learning models (Gaussian NB, Random Forest (RF), Logistic Regression (LR), Lasso Regression (Lasso), Support Vector Machine (SVM), Ridge Regression (Ridge) and Nearest Neighbor Algorithms (KNN)) in a comparative experiment. The experimental results showed that the EAPNet model was an efficient artifact detection method, with a detection accuracy of 69.44%, 77.21% and 80.01% for 2-way K-shot(K=1, 5, 10) tasks respectively. Among all the compared models, the EAPNet model had the highest recognition accuracy.
Normal EEG signals are susceptible to contamination by various EEG artifacts, resulting in low signal-to-noise ratios. In order to improve the signal-to-noise ratio of EEG signals, a metric-based few-shot learning method was used to detect EEG artifacts. A few-shot learning model named EEG Artifact Prototype Network (EAPNet) based on a prototype network was proposed to detect artifacts in EEG signals. The model was able to learn a nonlinear mapping from EEG features to the target space, calculate the distance of each class prototype representation and classify them according the distance. In addition, the EAPNet model required only a small number of examples of each new class to train the model to achieve accurate recognition of artifact signals. Artifact recognition experiments were conducted in the public EEG artifact dataset TUAR (TUH EEG Artifact Corpus). The EAPNet model is compared with 2 deep learning models (EEGNet, Fully Connected Neural Network (FNN)) and 7 machine learning models (Gaussian NB, Random Forest (RF), Logistic Regression (LR), Lasso Regression (Lasso), Support Vector Machine (SVM), Ridge Regression (Ridge) and Nearest Neighbor Algorithms (KNN)) in a comparative experiment. The experimental results showed that the EAPNet model was an efficient artifact detection method, with a detection accuracy of 69.44%, 77.21% and 80.01% for 2-way K-shot(K=1, 5, 10) tasks respectively. Among all the compared models, the EAPNet model had the highest recognition accuracy.
2022, 54(4): 121-128.
DOI: 10.6054/j.jscnun.2022066
Abstract：
An efficient two-party ECDSA threshold scheme is proposed to fix the problems of existing threshold ECDSA schemes, e.g., some signature protocols having too much computation overhead or too many interaction rounds, leading to low signature efficiency, and some signature protocols having OT (oblivious transfer) to replace the Paillier homomorphic encryption technology, increasing the communication cost by thousands of times. The scheme divides the signature private key into two parts to be kept by two parties respectively. Using the homomorphic encryption technology, each collaborative signature requires both users to participate in the signature process at the same time. In addition, the signature phase is divided into the offline precomputation phase and the online signature phase. Most of the computation is completed in advance in the offline precomputation phase. The online signature phase is efficient and fast, which improves the signature efficiency. The correctness analysis and security proof of the scheme are given, and the two ECDSA schemes proposed by Lindell and this current scheme are compared in terms of theoretical analysis. The results show that the scheme avoids the expensive homomorphic operation in the online signature phase and has the advantages of high signature efficiency, low communication cost, less interaction rounds and higher practicability.
An efficient two-party ECDSA threshold scheme is proposed to fix the problems of existing threshold ECDSA schemes, e.g., some signature protocols having too much computation overhead or too many interaction rounds, leading to low signature efficiency, and some signature protocols having OT (oblivious transfer) to replace the Paillier homomorphic encryption technology, increasing the communication cost by thousands of times. The scheme divides the signature private key into two parts to be kept by two parties respectively. Using the homomorphic encryption technology, each collaborative signature requires both users to participate in the signature process at the same time. In addition, the signature phase is divided into the offline precomputation phase and the online signature phase. Most of the computation is completed in advance in the offline precomputation phase. The online signature phase is efficient and fast, which improves the signature efficiency. The correctness analysis and security proof of the scheme are given, and the two ECDSA schemes proposed by Lindell and this current scheme are compared in terms of theoretical analysis. The results show that the scheme avoids the expensive homomorphic operation in the online signature phase and has the advantages of high signature efficiency, low communication cost, less interaction rounds and higher practicability.
