A two-step route was used to prepare SnO2/ZnO composite hetero-nanofibers. In the first step, hierarchical SnO2 nanofibers were synthesized by electrospinning; in the second step, ZnO nanospheres were fabricated in zinc acetate solution using water bath at 90 degrees C. The morphology, structure and composition of SnO2/ZnO composite hetero-nanofibers were characterized and analyzed by XRD, SEM, EDX, and XPS. SnO2 nanofibers in the composite materials keep hollow and hierarchical structure with 300 nm in diameter. The diameters of ZnO nanospheres grown on SnO2 nanofibers are 250-300 nm. Gas sensing properties of SnO2/ZnO composite hetero-nanofibers were tested using a static gas testing system. Gas sensing properties of pure SnO2 nanofibers and ZnO nanospheres were also studied to compare their gas sensing properties. The results show that SnO2/ZnO composite hetero-nanofiber gas sensors exhibit excellent sensing sensitivity, selectivity and long-tern stability for (0.5-100)x10(-6) acetone at 350 degrees C N-N homotype heterojunctions, existed in the joint between ZnO nanospheres and SnO2 particles in the SnO2/ZnO composite materials, change the potential barrier height. The absorption capacity of SnO2/ZnO composite materials increases greatly due to changes of the transport characteristics of electrons and holes, which results in the improvement of acetone sensing properties of SnO2/ZnO composite materials.

Three-dimensional hierarchical SnO2/ZnO hetero-nanofibers were fabricated by the electrospinning method followed with a low-temperature water bath treatment. These hierarchical hollow SnO2 nanofibers were assembled by the SnO2 nanoparticles through the electrospinning process and then the ZnO nanorods were grown vertically on the surface of SnO2 nanoparticles, forming the 3D nanostructure. The synthesized hollow SnO2/ZnO heterojunctions nanofibers were further employed to be a gas-sensing material for detection of volatile organic compound (VOC) species such as acetone vapor, which is proposed as a gas biomarker for diabetes. It shows that the heterojunction nanofibers-based sensor exhibited excellent sensing properties to acetone vapor. The sensor shows a good selectivity to acetone in the interfering gases of ethanol, ammonia, formaldehyde, toluene, and methanol. The enhanced sensing performance may be due to the fact that n-n 3D heterojunctions, existing at the interface between ZnO nanorods and SnO2 particles in the SnO2/ZnO nanocomposites, could prompt significant changes in potential barrier height when exposed to acetone vapor, and gas-sensing mechanisms were analyzed and explained by Schottky barrier changes in SnO2/ZnO 3D hetero-nanofibers.

Hierarchical structure In2O3 nanofibers were synthesized by traditional electrospinning technology. Then, In2O3 nanofibers were treated 30 min by using low-temperature RF oxygen plasma and hydrogen plasma, respectively. The morphology, structure, composition and element content of the In2O3 nanofibers modified by oxygen plasma and hydrogen plasma were characterized and analyzed by XRD, SEM, BET and XPS. After modification by plasma, the morphology, structure and element contents of the In2O3 nanofibers were significantly changed. Gas sensors were fabricated based on In2O3 nanofibers modified by oxygen plasma and hydrogen plasma, respectively. Gas sensing properties of modified In2O3 sensors were investigated by a static test system to a variety of VOC gases in the concentration range of 0.3-500 ppm. The test result shows that In2O3 gas sensor modified by oxygen plasma exhibits excellent acetone sensing properties, It indicates that surface adsorption properties of In2O3 nanofibers can be improved by surface modification technology using low-temperature RF plasma, so as to improve the gas sensing properties of sensors.

With the arrival of knowledge economy era and the shortening of product life cycle, information technology and the rapid development of e-commerce with each passing day, and customer gradually increasing expectations, the competition among enterprises are gradually entering the supply chain competition, Now enterprises have begun to realize that effective supply chain management, which would have to assess supply chain performance. However, most of the evaluation methods used in our country using expert analysis to evaluate the contractor's financial indicators to determine the final contractor. This method is not only too subjective, but also cuts off the correlation between the indicators. A quantitative management innovation classified performance model of supplier performance evaluation based on clustering and K-NN classification is proposed to classify suppliers. Then on the basis of above analysis, the contractor of misclassification is identified by the K-NN method. Finally, an evaluation and selection case is presented to verify the practicability and effectiveness of the model. The method not only overcomes the above shortcomings, but also reflects the contractor's comprehensive level objectively and fairly. The results show that it can provide an important reference for the fair and impartial evaluation of the project contractor as an important method for decision makers to select the contractor.

The Automobile Logistics Enterprises plays an important role in enhancing core competition strength of an enterprise ,improving added-value service, reducing cost of logistics and optimizing enterprise resources etc., but whether the above aims can be achieved depends on the ability and service of logistics vendors. It is of critical importance to the success of enterprise's outsourcing to choose an appropriate Automobile Logistics Enterprises vendor. While currently in China, the evaluating method we adopt are relay on analyzing the financial guideline of Automobile Logistics Enterprises evaluated by experts so as to ensure the final Automobile Logistics Enterprises. This method is not only too objective but also dissevers the connection between the biddings. Based on the construction of the index system for Automobile Logistics Enterprises classification, a method of classifying Automobile Logistics Enterprises is presented in this paper applying the cluster method of multivariate statistical analysis. It can be regarded as an important method for classifying Automobile Logistics Enterprises. Moreover, this method not only conquers the above drawbacks but also contributes to the selection of the Automobile Logistics Enterprises vendors on the basis of some objective information provided by this method.

In2O3/SnO2 composite hetero-nanofibers were synthesized by an electrospinning technique for detecting indoor volatile organic gases. The physical and chemical properties of In2O3/SnO2 hetero-nanofibers were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), Energy Dispersive X-Ray Spectroscopy (EDX), specific surface Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS). Gas sensing properties of In2O3/SnO2 composite hetero-nanofibers were measured with six kinds of indoor volatile organic gases in concentration range of 0.5~50 ppm at the operating temperature of 275 °C. The In2O3/SnO2 composite hetero-nanofibers sensor exhibited good formaldehyde sensing properties, which would be attributed to the formation of n-n homotype heterojunction in the In2O3/SnO2 composite hetero-nanofibers. Finally, the sensing mechanism of the In2O3/SnO2 composite hetero-nanofibers was analyzed based on the energy-band principle.

A four-sensor array with neural networks was developed to identify formaldehyde in three possible interfering volatile organic vapors, such as acetone, ethanol, and toluene. The sensor array consisted of four metal oxide-based gas sensors: two of them are commercial SnO2 sensors, other two sensors are made in our laboratory. The responses of the sensors to each gas and to the mixture of two or all of them were tested and evaluated. It was found that every sensor has response to these four kinds of gases, and the response value of each sensor to the mixture gases was lower than the simple added value of the responses to each gas. This phenomenon is due to the properties of gas and the sensing materials. For recognizing formaldehyde in the background of ethanol, acetone, and toluene in air, 108 gas samples were tested taking into account of possible practical concentrations. Among these samples, 91 samples were used for training the pattern recognition methods and 17 samples for testing the robustness. Three neural networks were used in this report, including back propagation neural network support vector machines (SVM) and extreme learning machine (ELM) with principal component analysis (PCA). The PCA helps to improve the accuracy of the ELM by preprocessing the sensor data, while the SVM method achieves the best accuracy. The ELM method indicates a better way to train the sensor array and to identify the particular gas species with very less training time and good accuracy.

La0.7Sr0.3FeO3 nanofibers with tunable hollow structures are prepared by a facile single capillary electrospinning and annealing process. The hollow nanofibers are characterized by thermogravimetry and differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen physisorption isotherms. The tunable hollow structures are controlled by adjusting the weight ratio of (La(NO3)3·6H2O + Sr(NO3)2 + Fe(NO3)3·9H2O)/PVP. With the increasing of nitrate/PVP ratio, the diameter and the shell thickness of hollow nanofibers increase. Formaldehyde gas sensing properties are carried out in the concentration range of 0.1–100 ppm at the operating temperature of 240 °C. The gas sensing mechanism is also discussed.

SnO2-ZnO composite nanofibers were synthesized by an electrospinning method in this study. The structural composition and morphology were characterized by X-ray diffraction, scanning electron microscopy and N2 physical adsorption. The results indicated that hollow hierarchical SnO2-ZnO composite nanofibers having mesopore structure formed after sintering at 600°C for 3h. The gas sensor prepared by the SnO2-ZnO composite nanofibers exhibited good selectivity to methanol in the presence of ethanol, acetone, formaldehyde, ammonia, toluene and benzene at the optimum operating temperature of 350°C. The response and recovery time to 10ppm methanol were about 20s and 40s, respectively. The growth mechanism of the hollow hierarchical nanofibers was discussed, as well as the methanol adsorption–desorption mechanism.

SnO2 nanofibers were fabricated by electrospinning, using SnCl2·2H2O as the raw material.The influences of ZnO doping on the morphologies, structures, and compositions of the SnO2 nanofibers were studied by introducing different amounts of ZnO into the SnO2. The crystallography and microstructures of the synthesized SnO2/ZnO composite nanofibers with different molar ratios of Sn to Zn were investigated using thermogravimetric/differential thermal analysis(TG-DTA), X-ray diffraction(XRD),Fourier- transform infrared(FTIR) spectroscopy, scanning electron microscopy(SEM), and energy dispersive X- ray(EDX) spectroscopy. The obtained SnO2/ZnO composite nanofibers with different ZnO contents had hollow hierarchical structures composed of nanocrystals. Different amounts of ZnO gave different structures. The characterization results showed that the introduction of ZnO into SnO2 played an important role in the SnO2 nanofiber structure. The gas sensing properties of sensors based on different ZnO-doped SnO2 nanofibers were tested. The results indicated that the methanol-sensing performance of the sensor containing SnO2/ZnO in a molar ratio of 1:1 was better than those of the others. The sensing mechanisms of ZnO-doped SnO2 nanofibers were examined in detail. Possible reasons for the enhancedresponse of the SnO2/ZnO-based sensor with a molar ratio of 1:1 are substitutional doping of Zn into SnO2 ,the catalytic effect of ZnO addition, and the inhibitory effect of excess ZnO, as well as the heterojunction across the SnO2 and ZnO interface.

La0.7Sr0.3FeO3 materials with morphologies including nanoparticles, nanorods and nanowires were synthesized via a hydrothermal process assisted with different cetyltrimethyl ammonium bromide (CTAB) concentration. XRD, SEM and BET were used to characterize the morphology, composition and structural properties of the nanomaterials. The effect of CTAB concentration on morphology and growth mechanism of La0.7Sr0.3FeO3 was discussed. The gas sensing properties of La0.7Sr0.3FeO3 materials with different morphologies were also carried out in 0.1 similar to 100 ppm formaldehyde.

Pure and yttrium- (Y-) doped (1 at%, 3 at%, and 7 at%) ZnO nanorods were synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersiveX-ray spectroscopy (EDX). Comparing with pure ZnO nanorods, Y-doped ZnO exhibited improved acetone sensing properties. The response of 1 at% Y-doped ZnO nanorods to 100 ppm acetone is larger than that of pure ZnO nanorods. The response and recovery times of 1 at% Y-doped ZnO nanorods to 100 ppm acetone are about 30 s and 90 s, respectively. The gas sensor based on Y-doped ZnO nanorods showed good selectivity to acetone in the interfere gases of ammonia, benzene, formaldehyde, toluene, and methanol. The formation mechanism of the ZnO nanorods was briefly analyzed.

SnO2/In2O3 composite nanofibers were synthesized by using an electrospinning system with double jets, then, treated by oxygen plasma. The morphology and structure of treated composite nanofibers were analyzed by SEM and XRD. The treated composite nanofibers showed more irregular and rough. The porosity of the treated composite nanofibers was bigger than the one of untreated. The gas sensing properties of the composite nanofibers to formaldehyde were measured before and after materials treated by oxygen plasma. The treated composite nanofibers exhibit large response values. Cross-responses and humidity effection of the treated composite nanofibers sensor were tested. The sensing mechanism of the SnO2/In2O3 composite nanofibers gas sensor treated by oxygen plasma was briefly analyzed.

Multi-wall carbon nanotubes (MWCNTs)-doped polyaniline (PANI) nanopowders were prepared by chemical oxidation polymerization. Then, the MWCNTs-doped PANI nanopowders were modified by a radio frequency (RF) oxygen plasma source. The morphology and structure of modified MWCNTs-doped PANI nanorods were analyzed by SEM and FI-IR. Gas sensors were fabricated based on plasma modified MWCNTs-doped PANI nanorods to detect ammonia at room temperature. The response amplitude of the gas sensor based on modified MWCNTs-doped PANI nanorods was much higher than those of MWCNTs-doped PANI nanopowders and pure PANI nanopowders sensors, respectively, in ammonia concentration range of 10–150 ppm. Cross responses of modified MWCNTs-doped PANI nanorods sensor to ammonia, ethanol, formaldehyde, and toluene were tested. The sensor showed good selectivity and stability. The sensing mechanism of modified MWCNTs-doped PANI nanorods gas sensor was analyzed.

A silicon-based micro-structure gas sensor for detecting formaldehyde was successfully fabricated and the sensing material was synthesized via a method of combining the traditional hydrothermal synthesis with subsequent heat treatment. Finite element analysis software of ANSYS was used to analyze the temperature distribution on the SiO2/Si substrate with heating electrodes and signal electrodes on the same plane with the aim of reducing the complexity of micro-machining process. Meanwhile, in order to obtain lower power consumption, two different structures of the SiO2/Si substrates with and without back etched were simulated, respectively. The simulation results showed that in the same heat rate and convection conditions, the back-etched SiO2/Si substrate had higher temperature, more uniform temperature distribution, and lower energy consumption. The Zn2SnO4/SnO2 cubes were obtained by annealing the as-synthesized precursors of ZnSn(OH)6 at 700 °C for 3 h. Thermal gravimetric and differential thermal analyzer, X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were analyzed to characterize the phase structure, composition, morphology, and elemental atomic ratio of Zn2SnO4/SnO2. The gas sensing properties of Zn2SnO4/SnO2 were tested, which showed that the gas sensor based on Zn2SnO4/SnO2 exhibited excellent formaldehyde sensing performance.

SnO2/In2O3 hetero-nanofibers composite was synthesized by using a modified electrospinning system with double jets of positive and negative polarity electric fields. The SnO2/In2O3 hetero-nanofibers with a netted structure composed of SnO2 and In2O3 nanofibers were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Both SnO2 and In2O3 nanofibers were hierarchical structures with many nanocrystallites. The SnO2 and In2O3 showed very different nanocrystallites sizes in the SnO2/In2O3 hetero-nanofibers composite. A gas sensor was fabricated based on SnO2/In2O3 hetero-nanofibers composite. The operating temperature of the gas sensor was 375°C. The response value of the gas sensor based on SnO2/In2O3 hetero-nanofibers was higher than the ones of SnO2 nanofibers and In2O3 nanofibers sensors, respectively, in formaldehyde concentration range of 0.5–50ppm. Cross-responses of SnO2/In2O3 hetero-nanofibers sensor to formaldehyde, ethanol, ammonia, acetone, toluene and methanol were tested. The response value of the SnO2/In2O3 hetero-nanofibers sensor decreased when the relative humidity increased. The sensing mechanism of the SnO2/In2O3 hetero-nanofibers gas sensor was briefly analyzed.

Indium oxide (In2O3) was synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The In2O3 had a flower-like hierarchical nanostructure and was composed of tiny near-spherical crystals with a diameter of approximately 20 nm. When In2O3 was mixed with CdO in a 1:1 molar ratio, it was found that the resulting In2O3/CdO composite showed an interesting grape-like porous microstructure following calcinations at elevated temperatures. A gas sensor using this In2O3/CdO composite as the sensing material showed higher sensitivity to different concentration of formaldehyde than the gas sensor based on pure flower-like In2O3 nanomaterials. The In2P3/CdO-based sensors showed a high sensitivity to a concentration of 0.05x10(-6) formaldehyde at the optimized operating temperature of 410 degrees C and a good level of selectivity over other possible interference gases such as ethanol, toluene, acetone, methanol, and ammonia. The gas sensing mechanism of In2O3/CdO sensor has been discussed in detail.

ZrO2:TiO2 hetero-nanofibers composite was synthesized via electrospinning with double jets based on positive and negative polarity electric fields. The hetero-nanofibers were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). ZrO2:TiO2 composite shows a netted hetero-nanofibers structure with interleaving of two different diameters nanofibers. Humidity sensors were fabricated based on ZrO2:TiO2 hetero-nanofibers. The impendence of the sensor changed four orders of magnitude from 105 to 101 kΩ in relative humidity (RH) range of 11–97% at 25 °C. The max humidity hysteresis was around 5% RH, and the response and recovery times were less than 5 s and 20 s, respectively. The properties of impendence vs. RH at different temperatures were discussed. Overall, the humidity sensor of ZrO2:TiO2 hetero-nanofibers exhibited good sensing characteristics. The humidity sensing mechanism was analyzed via dielectric loss and equivalent circuit.