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This paper presents a study on the influence of different rectifiers on a super-high-speed permanent magnet generator (SHSPMG), which is used in a micro-gas turbine distributed generation system. T...

As the core of the distributed generation system, the health status of high-speed permanent magnet generator (HSPMG) has attracted much attention. HSPMG is often used in military, rescue and other fields. When the open-circuit fault of HSPMG stator winding occurs, it will seriously affect the operation stability and power supply reliability. In this study, a 117 kW, 60,000 rpm HSPMG is taken as an example, and a 2D finite element model is established. The accuracy of the model is verified by comparing the calculated results with the experimental data. By the field-circuit coupling method, the magnetic field changes pre-and post-fault is analysed, and the mechanism of magnetic field spatial distribution changes post-fault is revealed. In addition, the changes in eddy current loss pre-and post-fault are analysed. The influence of the harmonic magnetic field and the rotating magnetic field produced by negative sequence current on eddy current loss is studied, and the dominant factors effecting eddy current loss post-fault are investigated. The study provides some useful conclusions for HSPMG fault analysis.

The fascinating research is the first book to study Chinese diaspora in museums; it comprises an introduction, four parts and a conclusion. The data was collected during the author’s field visits t...

Drought risk management can effectively reduce drought losses and improve drought resistance capability, of which drought risk assessment is the core issue. This study evaluated the agricultural drought risk in Huaibei Plain of Anhui Province in China by the approach of constructing drought loss risk curves and risk distribution maps. The results showed that: 1) The drought events that occurred in northern regions (Huaibei and Suzhou) were with the characteristics of high-frequency and low-intensity, while in southern regions (Huainan and Bengbu), the occurring characteristics were low-frequency, high-intensity, and long-duration. 2) Without irrigation, Fuyang was the high-risk region with more than 80% potential yield loss rate, while Huainan was the relatively low-risk area with a potential yield loss of 50%. 3) Irrigation had a significant effect on reducing drought risk loss, while the efficiency was influenced by the spatio-temporal distribution of precipitation. The irrigation scheme in study area still remains to be optimized based on the characteristics of precipitation and crop growth. This study established and practiced a quantitative framework for regional drought risk assessment by creating drought risk curves and risk maps, which have significant value in improving the regional agricultural drought risk management level.

The permanent magnet thickness (PMT) is an important parameter in the design of the permanent magnet machine, and it directly affects the air-gap magnetic field and performance of generator. In this paper, a 117-kW, 60,000-rpm, high-speed permanent magnet generator (HSPMG) is taken as an example, and a two-dimensional finite element model (FEM) is established. By comparing calculation result and test data, the accuracy of the model is verified. The air-gap flux density waveform is obtained by the FEM, and the waveform is decomposed by the Fourier transform principle. The nonlinear variation law of harmonic content with the increase in PMT is obtained, and the nonlinear variation mechanism of air-gap flux density is revealed. On this basis, the variation law of voltage and voltage regulation with the increase in PMT is given, and the PMT is optimized. In addition, the nonlinear variation law of the loss is determined. The research shows that the purpose of optimizing performance of HSPMG can be achieved by adjusting the PMT. The PMT is finally determined when the generator performance is optimal. The conclusions provide some reference for the research of HSPMG.

The primary problem brought by high speed is high-frequency loss. The loop current (LC) of inter-turn short-circuit fault causes serious distortion of the magnetic field in high speed permanent magnet generator (HSPMG), whose effects on the loss cannot be ignored. In order to reveal the influence mechanism of ITSC fault on the loss, the two-dimensional finite element model of the 117 kW, 60,000 rpm HSPMG is established. By comparing calculation results and test data, the accuracy of the model is verified. The distribution of the eddy current density is studied, and the fundamental reason for the sharp increase of eddy-current loss after fault is found. The core losses at different positions were obtained by segmenting stator core, and the variation mechanisms of core losses at different positions are revealed. The change of heat source distribution of stator core after fault is determined. The variation of winding copper loss after fault is analysed, and the influence degree of the LC on the fault phase and healthy phase copper loss is determined. In addition, because the temperature field is directly related to the loss, the research also laid a foundation for the next analysis of the temperature field.

As a kind of emergency power supply in military field, the high-speed permanent magnet generator (HSPMG) has attracted wide attention to its healthy condition. The loop current (LC) of the inter-turn short-circuit (ITSC) fault seriously endangers the generator unit operation stability and power supply reliability. In order to study the influence of pulsating magnetic field produced by LC on the electromagnetic field, the two-dimensional finite element model (FEM) of the 117 kW, 60000 rpm HSPMG is established. By comparing calculation result and test data, the accuracy of the model is verified. The field-circuit coupling method is used to reveal the change mechanism of magnetic field symmetry when ITSC fault occurs. By comparing the spatial distribution of the air-gap flux density, the relationship among the spatial distribution of the air-gap flux density, the elliptical rotating magneto-motive force (MMF) and the current phase angle is determined. The variation of the amplitude of the air-gap flux density space harmonic under different fault degree is studied, and the fault characteristics of ITSC fault are obtained, which provides a reference for ITSC fault diagnosis and fault degree identification. In addition, the research also laid a theoretical foundation for the next analysis of the loss and temperature field.

Urban floods are a common urban disaster that threaten the economy and development of cities. Sponge cities can improve flood resistance ability and reduce floods by setting low-impact development measures (LID). Evaluating flood reduction benefits is the basic link in the construction of sponge cities. Therefore, it is of great significance to evaluate the benefits of sponge cities from the perspective of different rain patterns. In this study, we investigated the urban runoff of various rainfall patterns in Mianyang city using the Strom Water Management Model (SWMM). We employed 2–100-year return periods and three different temporal rainfall downscaling methods to evaluate rain patterns and simulate urban runoff in Mianyang, with and without the implementation of sponge city measures. After calibration, model performance was validated using multi-source data concerning flood peaks and inter-annual variations in flood magnitude. Notably, the effects of peak rainfall patterns on historical floods were generally greater than the effects of synthetic rainfalls generated by temporal downscaling. Compared to the rainfall patterns of historical flood events, the flood protection capacities of sponge cities can be easily overestimated when using the synthetic rainfall patterns generated by temporal downscaling. Overall, an earlier flood peak was associated with better flood sponge city protection capacity. In this context, the results obtained in this study provide useful reference information about the impact of rainfall pattern on urban flood control by LID, and can be used for sponge city design in other part of China.

As an emergency power supply, the reliability of high-speed permanent magnet generator (HSPMG) must be guaranteed. However, affected by armature reaction, the variation of power factor will cause the changes of the loss and temperature field, which leads to the risk of permanent magnet (PM) demagnetization. In addition, regulating power factor is also the most effective way to improve the utilization of power resources. It is particularly important to select a reasonable power factor. In this paper, the influences of power factor on losses, especially on sleeve and PM eddy current loss, are determined by field-circuit coupling method. The variation mechanism of the loss is revealed. Furthermore, based on the losses study, a 3D model for calculating temperature field is established by applying hydrodynamics and heat transfer theory. The temperature distributions under different power factors are studied, and the sensitivity of temperature to power factor is determined. The power factor at the PM working temperature limit is found. The research not only assists generator designers to select power factor, but also provides early warning for PM high temperature demagnetization to improve HSPMG reliability.

In an agricultural drought risk system, crop drought loss sensitivity evaluation is a fundamental link for quantitative agricultural drought loss risk assessment. Summer maize growth processes under various drought patterns were simulated using the Cropping System Model (CSM)-CERES-maize, which was calibrated and validated based on pit experiments conducted in the Huaibei Plain during 2016 and 2017 seasons. Then S-shaped maize drought loss sensitivity curve was built for fitting the relationship between drought hazard index intensity at a given stage and the corresponding dry matter accumulation and grain yield loss rate, respectively. Drought stress reduced summer maize evapotranspiration, dry matter, and yield accumulation, and the reductions increased with the drought intensity at each stage. Moreover, the losses caused by drought at different stages were significantly different. When maize plants were exposed to a severe water deficit at the jointing stage, the dry matter and grain yield formation were greatly affected. Therefore, maize growth was more sensitive to drought stress at the jointing stage when the stress was serious. Furthermore, when plants encountered a relatively slight drought during the seedling or jointing stage, which represented as a lower soil water deficit intensity, the grain yield loss rates approached the maximum for the sensitivity curves of these two stages. Therefore, summer maize tolerance to water deficit at the seedling and jointing stages were weak, and yield formation was more sensitive to water deficit during these two stages when the deficit was relatively slight.

Drought loss risk curves can quantitatively assess regional drought and indicate the mechanism of drought hazards. In this study, the drought events were identified using the run theory based on Standard Precipitation Index (SPI) and Composite meteorological drought Index (CI) separately calculated by daily weather data during 1955–2012. The frequency of drought events was calculated by using the Copula function. The yield loss of soybeans under different irrigation levels in dry years was simulated by DSSAT-CROPGRO-soybean model. Finally, the regional drought risk for soybeans in Bengbu city was analyzed by constructing a series of relationship curves among the drought frequency, soybean drought loss, and the irrigation level. The results indicated that (1) both the SPI and CI were applicable to identifying drought events in the selected city, but SPI was more sensitive in identifying short-term drought events, and CI was more reliable in recognizing medium-term drought events. (2) The frequency of drought events during the target crop's growing period and the corresponding yield loss rate satisfied the semi-logarithmic function, and the average values of their determinant coefficients were 0.68 and 0.74 based on SPI and CI, respectively. (3) Irrigation could significantly reduce soybean yield loss in non-extreme drought events. Therefore, drought loss risk curves can reflect regional drought risk more quantitatively and facilitate the assessment and management of regional drought risk.

It is significant to develop new sorbents with high affinity and good selectivity for uranium extraction from aqueous solution. We herein developed a new type of sorbent based on SBA-15 with covalently attached positive charge and phosphate group for uranium extraction. High selectivity and fast kinetics for uranium (VI) sorption can be achieved by the functional material, which may be originated from the cooperative effect of positive charges: the negative uranium complex would be attracted by electrostatic interaction, while the other metal cations were repelled. The functional materials could be efficiently regenerated and reused with high sorption efficiency after five cycles. This work may provide a new approach for efficient sorption of uranium from aqueous solution.

To quantitatively access the effects of drought stress during different growth stages of soybean on development process and yield, a pot-culture experiment was conducted in China&rsquo, s Huaibei Plain with different irrigation treatments over two seasons (2015 and 2016). Two drought stress levels (mild and severe) were applied at four growth stages for the experiment (S: seedling stage, B: branching stage, FPS: flowering and pod-setting stage, and PF: pod-filling stage). The effects of drought stress at different stages on growth and yield were evaluated and compared. Results of this two-year study showed that all growth and yield parameters were significantly affected by the water deficit during the sensitive FPS. Compared to the full irrigation treatment, severe drought stress during FPS caused a 22% loss of final plant height, 61% loss of the leaf area per plant (LAP), and 67% loss of final aboveground dry matter (ADM). Yield components also declined dramatically with water deficits during FPS and PF. Significant seed yield losses of 73&ndash, 82% per plant were observed in the plants exposed to drought stress during FPS, and were also associated with the highest nonviable pod percentage of 13%. The greatest losses in 100-seed weight (42&ndash, 48%) were observed under drought stress during PF. A rising trend in response to increasing soil water deficit (SWD) was observed for LAP, yield, and ADM losses. The slope (k) values of these fitting curves varied at different treatments, the highest value of k (7.37 and 8.47 in two years, respectively) was also observed in the sensitive FPS.

It is significant for environment and human health to develop new materials for the sorption of radioactive technetium. We report herein a novel method to synthesize surface ion-imprinted magnetic microspheres for efficient capture of technetium ions. Specifically, perrhenate anion as the structural surrogate for pertechnetate anion, was employed as template to prepare ion-imprinted magnetic microsphere by “one-pot” radical polymerization and quaternization. The sorption behavior is closely related with the surface chemical composition: the more nitrogen content, the higher sorption efficiency. The sorption is an exothermic spontaneous sorption process and kinetically followed pseudo-second-order model. A sorption capacity of 62.8 mg of Re/g could be achieved at 298.15 K and pH = 6. Compared with non-imprinted composites, imprinted microspheres showed higher selectivity, faster kinetics, and larger sorption capacity of perrhenate ions. This work may provide a promising approach for the efficient sorption of pertechnetate.

The development of sorbent for uranium seawater extraction is critical for guaranteeing future uranium resources for nuclear energy. An amidoxime-based cationically charged fibrous sorbent is reported here for potential uranium extraction from seawater. Specially, poly(1-vinylimidazole) was grafted onto polypropylene nonwoven fabric under γ-ray irradiation and was followed by quaternization and amidoximation to give the fibrous sorbent. The sorption could reach equilibrium with a capacity of 119.76 mg U/g within 50 h at pH 8.0 and 298.15 K. Compared with the uncharged sorbent, the cationic sorbent showed faster kinetics, higher selectivity, and larger capacity for uranium extraction. This work indicates that the cationically charged poly(amidoxime)-grafted nonwoven fabric may be a potential promising sorbent to extract uranium from seawater.

Interaction between peptide and lipid membrane plays a major role in biological activity of membrane-active peptide. We describe here a new biocompatible polymeric assembly to support membrane peptide. Specifically, chitosan-graft-poly(sulfobetaine methacrylate) (CS-g-PSBMA) was synthesized for alamethicin assembly by controlled polymerization under γ-ray irradiation. The graft copolymer could self-assemble into micelles in distilled water for supporting alamethicin. The assembly of alamethicin with CS-g-PSBMA micelles in aqueous solutions was related with the ratio of alamethicin/CS-g-PSBMA: the more alamethicin, the smaller sizes of the hybrid complex. Moreover, alamethicin penetrated into the hydrophobic cores of CS-g-PSBMA micelles while displayed secondary helical conformation in the complex. The results indicate that CS-g-PSBMA assemblies can be used to support membrane peptide.

It is of strategic and ecological importance to capture uranium(VI) from aqueous solutions. A novel strategy is reported herein to synthesize bifunctional polymeric microspheres for efficient uranium removal from aqueous solution. Specifically, positively charged microspheres with amidoxime groups were prepared by emulsion polymerization. The high selectivity and fast kinetics for uranium(VI) can be achieved by the microspheres via the synergistic interaction of positive charge and coordinating ligand. The negative uranium tricarbonate complex would be adsorbed to the positively charged microspheres by coulombic interaction without interference of other metal cations, and the coordination may occur with amidoxime groups via ligand exchange. It is calculated that nearly 36% of the adsorbed uranium(VI) is due to coulombic interactions of the positive charge while 64% is due to coordination of amidoxime groups. To the best of our knowledge, this is the first report on colloidal particles with positive charges and ligand groups for uranium(VI) uptake from aqueous solution.

The colloidal particles with switchable surfaces (i.e. smart surfaces) have attracted great attention for numerous potential industrial applications. We report here a novel approach for the fabrication of polymeric particles with smart surfaces by emulsion polymerization using “giant” surfactant. Specifically, the “giant” surfactant was obtained by incorporating poly(4-vinylpyridine) chains onto the one bulb of snowman-shaped polystyrene particles, and then used as emulsifier for the emulsion polymerization at pH = 2.00. The nearly monodisperse waxberry-like polystyrene particles were prepared with dual-size roughness surfaces, and the particulate film exhibited reversibly pH-switchable superhydrophobic property due to the pH-sensitivity of P4VP chains and the surface topology. This property enabled the particles could be used to effectively sequester hazardous anions from the wastewater.

We report a novel chitosan derivative, chitosan-ionic liquid (CS-IL) conjugation for anion adsorption. Specifically, CS-IL conjugation was synthesized through the reaction of amino groups of chitosan with carboxylic groups of 1-carboxybutyl-3-methylimidazolium chloride. Due to the amphiphilic structure, CS-IL conjugation could self-assemble into nanoparticles in distilled water. This novel chitosan derivative revealed good anion adsorption performance, and the adsorption capacity of Cr2O7(2-) and PF6(-) was 0.422 mmol/g and 0.840 mmol/g, respectively. The adsorption of Cr2O7(2-) and PF6(-) could be improved at low pH, which was ascribed to the adsorption of protonated NH2 on chitosan. Importantly, the chitosan derivative would aggregate in the water after the adsorption and could be easily separated. The properties enable CS-IL conjugation to be used as a novel anion adsorbent for wastewater treatment.