Zuopeng Li

Land-use change analysis in Yulin prefecture, northwestern China using remote sensing and GIS

Rapid land-use change has taken place in many arid and semi-arid regions of China such as Yulin prefecture over the last decade due to rehabilitation measures. In this paper, land-use change dynamics were investigated by the combined use of satellite remote sensing and geographical information systems (GIS). Our objectives were to determine land-use transition rates among land-use types in Yulin prefecture over 14 years from 1986-2000 and to quantify the changes of various landscape metrics using FRAGSTATS, the spatial pattern analysis program for Categorical Maps. Using 30-m resolution Landsat Thematic Mapper (TM) data from the Institute of Remote Sensing Application (IRSA) in China, we classified images into six land-use types: cropland, forestland, grassland, water, urban and/or built-up land, and barren land. Significant changes in land-use occurred within the area over the study period. The results show the significant decrease in barren land was mainly due to conversion to grassland. Cropland increased by 3.39%, associated with conversions from grassland and barren land. The landscape has become more continuous, clumped and more homogeneous. The study demonstrates that the integration of satellite remote sensing and GIS was an effective approach for analysing the direction, rate and spatial pattern of land-use change.

Clean Beckmann rearrangement of cyclohexanone oxime in caprolactam-based Brønsted acidic ionic liquids

The Beckmann rearrangement of cyclohexanone oxime to afford caprolactam in a novel caprolactam-based Bronsted acidic ionic liquid as catalyst and reaction medium proceeded with high conversion and selectivity at 100 °C. The occurrence of the Beckmann rearrangement of cyclohexanone oxime in such a Bronsted acidic IL was also confirmed with in situ FT-Raman observation. The key point is that the caprolactam product was one component of the ionic liquid, and a dynamic exchange between the resulting caprolactam product and the caprolactam from the ionic liquid is expected. Therefore, the strong chemical combination between the caprolactam product and the acidic ionic liquid was greatly decreased and the desired product in the solid was recovered through extraction with organic solvent after the reaction.

Controlling Iron‐Catalyzed Oxidation Reactions: From Non‐Selective Radical to Selective Non‐Radical Reactions

Among all elements widely distributed in nature, iron is probably the most versatile and important redox center for life and natural transformation processes. With respect to sustainable chemistry and following nature s principles, iron is the ideal metal for more environmentally benign catalyst generations in future because of availability, low toxicity, and price. Although iron plays wonderfully in nature, the difficulty to prevent non-selective radical reactions makes its usage on laboratory scale, but especially for industrial production, more difficult—except being directly used as Lewis acid. In order to apply iron catalysts for a specific reaction with sufficient selectivity and activity, so far the general concept is based on the design of a suitable ligand which is further on optimized. In recent years iron catalysis has become a “hot topic” and notable progress has been accomplished applying this approach. For instance, novel iron containing systems have been developed for hydroxylation, sulfide oxidation, cross-coupling reactions, heterolytic RO OH bond cleavage, hydroamination, allylic alkylation or amination, epoxidation, and alcohol oxidation. However, the intrinsic problem of nonselective radical side-reactions in the redox chemistry of iron has not been generally solved. This is especially evident for Fentonor Gif-type reactions, that is, Fe with H2O2, which constitute one of the most famous iron salt-dependent systems. Its high efficiency for oxidations of alkanes to ketones, benzene to phenol, and for environmental pollutant treatment has been extensively explored and has significant industrial potential. Notably, after more than a century of the first report, detailed investigations of the Fenton reaction still reveal two possible mechanisms, that is, the classical free radical mechanism and the oxygenated Fenton chemistry. Until today there is no concrete evidence to exclude each other completely, because both mechanisms have their own supporting evidence. In former reports, the importance of acids in Fenton chemistry has been studied, however a detailed study on the crucial function of pH variation on the catalyst activity and selectivity has been ignored. Earlier on, we discovered the pH dependency of the selectivity in osmium-catalyzed dihydroxylations of olefins applying oxygen as the terminal oxidant. Based on our recent experience in iron catalysis, we supposed that the proton concentration in the reaction system might be also important for Fe-dependant oxidation reactions. Indeed, studying the oxidation of benzyl alcohol to benzaldehyde as a typical model reaction, a remarkable influence of the pH is observed (Table 1).

Novel cyclic sulfonium-based ionic liquids: synthesis, characterization, and physicochemical properties.

A new series of ionic liquids composed of three cyclic sulfonium cations and four anions has been synthesized and characterized. Their physicochemical properties, including their spectroscopic characteristics, ion cluster behavior, surface properties, phase transitions, thermal stability, density, viscosity, refractive index, tribological properties, ion conductivity, and electrochemical window have been comprehensively studied. Eight of these salts are liquids at room temperature, at which some salts based on [NO(3)](-) and [NTf(2)](-) ions exhibit organic plastic crystal behaviors, and all the saccharin-based salts display relatively high refractive indices (1.442-1.594). In addition, some ionic liquids with the [NTf(2)](-) ion exhibit peculiar spectroscopic characteristics in FTIR and UV/Vis regions, whilst those salts based on the [DCA](-) ion show lower viscosities (34.2-62.6 mPa s at 20 degrees C) and much higher conductivities (7.6-17.6 mS cm(-1) at 20 degrees C) than most traditional 1,3-dialkylimidazolium salts.

Experimental system for the study of the directional thermal emission of natural surfaces

A new automatic experimental system was designed to improve the accuracy of multidirectional thermal infrared measurements. This experimental system mainly consists of two identical thermal cameras operating at 8–13 µm, one metal ring to keep the constant view area for different view angles and a goniometer, which is composed of: (1) a semicircular roadway of 2 m diameter to change the observation angle in the azimuth direction; (2) an elevator of 1 m height to adjust the measuring level to the target level; (3) a rotating arm equipped with one thermal camera for changing the observation angle in the zenith direction; and (4) a fixed arm equipped with another thermal camera to record at nadir the target temperature variation with time during the measurements. The system can be disassembled for easy transport and all of the data acquisition procedures are automatically monitored. For a given azimuth angle, the system needs about 2 minutes to make the directional measurements from about −70° to 70°, and for completing one hemispheric measurement it needs about 20 minutes if the multidirectional measurements are conducted by a step of 30° in the azimuth direction. The preliminary data acquired using our new system on bare soil and winter wheat are displayed and analysed. The results show that the angular variation of surface brightness temperature is measurable and presents some regular directional distribution and can be used quantitatively to study the directional thermal emission of the natural surfaces.

Dialkoxy functionalized quaternary ammonium ionic liquids as potential electrolytes and cellulose solvents

A series of new ionic liquids, based on dialkoxy-functionalized quaternary ammonium cations {side chains: 1 = CH3, 1O1 = CH3OCH2, 1O2 = CH3OC2H4, 2O2 = C2H5OC2H4; cations: [N11,1O1,1O2], [N11,1O1,2O2], [N11,1O2,1O2], [N11,1O2,2O2] and [N11,2O2,2O2]}, with BF4−, (CF3SO2)2N− (NTf2) and CH3CO2− (OAc) as counteranions, have been prepared and characterized. Their basic properties, such as spectroscopic characteristics, melting point, glass transition temperature, thermal stability, electrochemical window, density, refractive index, viscosity and conductivity, were measured and comparatively studied. The incorporation of two flexible alkoxy chains makes the quaternary ammonium salts highly qualified to be low-viscous and high-conductive room temperature ILs, and even some of them have significantly better fluidity than the popular imidazolium ILs with a similar molecular weight, e.g.[N11,1O1,2O2]BF4 (151 cP and 2.11 mS cm−1, Mw: 249) vs.[HMIm]BF4 (220 cP and 1.2 mS cm−1, Mw: 256) at 25 °C. The electrochemical windows of these ILs were evaluated up to 5.5 V. In addition, the dialkoxy OAc ILs were found to have excellent solvent power for cellulose under mild conditions, e.g. a solution of 18 wt% microcrystalline cellulose in [N11,2O2,2O2]OAc at 80 °C. By precipitation with water, the dissolved cellulose (I crystal structure) was regenerated as nanosized cellulose II particles with increased surface area and decreased crystallinity, determined by FE-SEM and XRD.

Temporal and spatial soil moisture change pattern detection in an agricultural area using multi‐temporal Radarsat ScanSAR data

Monitoring the characteristics of spatially and temporally distributed soil moisture is important to the study of hydrology and climatology for understanding and calculating the surface water balance. The major difficulties in retrieving soil moisture with Synthetic Aperture Radar (SAR) measurements are due to the effects of surface roughness and vegetation cover. In this study we demonstrate a technique to estimate the relative soil moisture change by using multi‐temporal C band HH polarized Radarsat ScanSAR data. This technique includes two components. The first is to minimize the effects of surface roughness by using two microwave radar measurements with different incidence angles for estimation of the relative soil moisture change defined as the ratio between two soil volumetric moistures. This was done by the development of a semi‐empirical backscattering model using a database that simulated the Advanced Integral Equation Model for a wide range of soil moisture and surface roughness conditions to characterize the surface roughness effects at different incidence angles. The second is to reduce the effects of vegetation cover on radar measurements by using a semi‐empirical vegetation model and the measurements obtained from the optical sensors (Landsat TM and AVHRR). The vegetation correction was performed based on a first‐order semi‐empirical backscattering vegetation model with the vegetation water content information obtained from the optical sensors as the input. For the validation of this newly developed technique, we compared experimental data obtained from the Southern Great Plain Soil Moisture Experiment in 1997 (SGP97) with our estimations. Comparison with the ground soil moisture measurements showed a good agreement for predication of the relative soil moisture change, in terms of ratio, with a Root Mean Square Error (RMSE) of 1.14. The spatially distributed maps of the relative soil moisture change derived from Radarsat data were also compared with those derived from the airborne passive microwave radiometer ESTAR. The maps of the spatial characteristics of the relative soil moisture change showed comparable results.

Retrieval of land surface bidirectional reflectivity in the mid-infrared from MODIS channels 22 and 23

This paper proposes a method to retrieve the land surface bidirectional reflectivity ρb in the mid‐infrared (MIR) from MODIS channels 22 and 23. A split‐window‐like algorithm was developed to determine the MIR ground brightness temperature without the contribution of the solar direct beam from ground brightness temperatures measured at two adjacent MIR channels. Comparing the actual values of ρb with those estimated using our proposed method, the root mean square error (RMSE) was determined to be 0.0022 for the solar zenith angle (SZA) at nadir. Similar results were obtained for other SZAs, indicating that the proposed method can retrieve ρb accurately. A detailed sensitivity analysis found that the effects of instrumental noise, variations in water vapour content in the atmosphere, and reasonable variations in horizontal visibility on the retrieval of ρb were negligible and an error of 1 K on the ground brightness temperature caused by the inaccuracy of atmospheric corrections can lead to a maximum error of 0.034 on the retrieved ρb. We compared the use of radiosonde data and European Centre for Median‐range Weather Forecast (ECMWF) atmospheric data to perform atmospheric corrections. The results show that atmospheric corrections can be performed with ECMWF data instead of radiosonde data without losing the accuracy of the retrieved ρb. MODIS land surface temperature/emissivity product MOD11B1 data were also used to validate . Comparison of estimated respectively with the proposed method and with MOD11B1 data showed that the RMSE is less than 1 K for cloud‐free skies.

Effect of body size and larval experience on mate preference in Helicoverpa armigera (Hübner) (Lep., Noctuidae)

Abstract:  We studied the mating selection in the cotton bollworm, Helicoverpa armigera (Hübner), in relation to body size and larval diet in the laboratory. When provided with an artificial diet at larval stage, weight, body and forewing length did not affect the probability of a male/female moth being selected for mating, but the abdominal width of selected female moths was significantly wider than that of non‐selected female moths. 30 female moths were dissected and number of eggs was counted after mating, and there was a correlation between the abdominal width and egg number. There was also significant difference of weight loss between selected and non‐selected male/female moths after the mating. The effect of operational sex ratio on mating latency and copulation duration were tested, and the result indicated that mating latency of male selection was significantly longer than that of female selection, but the difference of copulation duration was not significant. Cotton, corn and peanut plants were provided to larvae to test the effect of larval host plant experience on mate choice. When cotton‐ and peanut‐fed moth severed as potential partners, both female and male of cotton‐fed moths significantly preferred cotton‐ to peanut‐fed moths for mating. The possible reasons for mate preference based on larval host plant experience may account for host plants attributes on sex pheromone variation and sexual maturity. These findings may impact Bacillus thuringiensis resistance management.

Multi‐layer perceptron neural network based algorithm for estimating precipitable water vapour from MODIS NIR data

This Letter presents a multi‐layer perceptron neural network (MLP‐NN) based algorithm to quantitatively determine precipitable water vapour (PWV) directly from near infrared (NIR) radiance measured by the Moderate Resolution Imaging Spectroradiometer (MODIS). First, the background of the MLP‐NN based algorithm is discussed briefly. Then, the radiance of MODIS NIR channels simulated through a radiative transfer model with a set of input variables covering a broad range of surface reflectance and water vapour content are used to train MLP‐NN. Finally, PWV values derived by the MLP‐NN based algorithm are compared with radiosonde observations and a root mean squared error of 5.2 kg m−2 is found from this comparison.