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Eddy current analysis is a key issue for large turbine generators. The finite-element method (FEM) is a computational tool for obtaining the electromagnetic characteristics of electrical machines. In this article, we propose a computer model of the eddy current losses of metal fasteners in the rotor slots of a large turbine generator. The electromagnetic properties of the rotor fasteners and the outer diameter of the rotor are taken as the input, and the eddy current loss of the rotor fasteners is taken as the output. A prediction model is constructed using the FEM and deep learning. The analysis results show that compared with the independent finite-element analysis, this method reduces the design cycle time and improves the design efficiency for a large-capacity turbine generator. Compared with other machine learning models, the error is smaller and the accuracy is higher. This method provides a new way to accurately predict the eddy current loss of a generator under complex nonlinear conditions.

A method combining the finite-element method (FEM) numerical calculation with machine learning is developed and used to calculate the eddy current losses of the rotor damping slot wedge of generator with different structures and electromagnetic properties. FEM simulation data is used as the input, and the stacking method is used to build the ensemble Gaussian process regression model for eddy current loss prediction to predict and analyse the calculation results. The error is tiny. The FEM results are highly consistent with the prediction data. As demonstrated by comparison experiments, the prediction accuracy of the stacking Gaussian process regression (SGPR) model is greater than that of other models. Therefore, the SGPR model provides a new auxiliary design method for large generators that can help improve generator design efficiency.

For large generators, accurate assessment for the resistance enhancement coefficient (REC) and thermal dissipation is of great significance. With the development of design and manufacturing technology for large generators, the different cross section of the upper and lower strand becomes an effective method to reduce the heat losses. In current electromagnetism design, the eddy current analysis does not take the strand structures into account. In this paper, the REC of strands with special structures of a 150MW turbo-generator is derived by an analytic algorithm. Besides that, a mathematical model of the stator slot is established and the heat losses distribution and REC of strands are calculated by finite element method (FEM). On this basis, the stator REC and thermal dissipation of a 1000MW power turbo-generator are investigated with hollow and solid strands. The calculated results match the experimental data. All of these could provide an important theoretical basis and reference for the design of stator windings in high-power generators.

A combination of fused deposition modeling printing with atomic layer deposition (ALD) of titania was designed to achieve templated biomineralization and terminal odontogenic differentiation of dental pulp stem cells on three-dimensional (3D) printed polylactic acid (PLA) scaffolds. In the absence of the ALD-deposited titania coating, we had previously shown that both plating efficiency and differentiation are adversely impacted when scaffolds are produced by 3D printing rather than traditional polymer molding. These differences were removed when both printed and molded structures were coated with ALD of titania, which improved the outcomes regardless of the manufacturing method. In this case, on all titania-coated substrates, the plating efficiency increased, copious mineral deposition was observed, and RT-PCR indicated a significant upregulation of osteocalcin, a gene associated with mineral deposition. The influence of additional coatings of collagen, gelatin, or fibronectin on the ALD titania-coated and uncoated PLA-printed and molded scaffolds was also investigated. Upregulation of the odontogenic late-stage differentiation sibling protein, dentin sialoprotein, was observed on the collagen ALD-titania-coated scaffolds and to a lesser extent on the gelatin ALD-titania-coated scaffolds.

The driving motor for the cooling medium in a high-temperature gas-cooled reactor is crucial for the coolant circulation in the reactor. This paper proposes a method for calculating the gas friction loss using Bernoulli's equation to study its effect on temperature rise in the motor. The ventilation network model of the motor was developed using the fluid network method, and a three-dimensional mathematical model of the stator was established by considering the relationships between the fluid velocity, temperature, and gas friction loss. The results of the ventilation system calculations were applied to the physical model as boundary conditions, and the distribution of the stator temperature was determined using the finite-volume method. The effect of the change in the stator ventilation structure on the gas friction loss distribution was studied. The calculated friction losses accorded well with the values obtained using the empirical formula for the gas friction loss.

The weldability is essential for the practical applications of conductive adhesion. In this paper we focused on the weldability through microstructure, bonding strength, and shear strength of welding spot with co-doping of metal material Al and oxide material ZnO. When Al and ZnO doped separately, it can be seen from the results that Al-doping would increase the volume resistivity and adhesion strength for welding spot, and a proper amount of ZnO-doping would decrease the volume resistivity and improve adhesion strength for welding spot. Co-doping with Al and ZnO could decrease volume resistivity and enhance adhesion strength of welding spot concurrently, and the typical properties were 1.119 × 10−4 Ω cm for volume resistivity, 34.84 MPa for shear strength, and 17.00 MPa for bonding strength with addition of 4 wt% Al and 7 wt% ZnO.

To research the temperature rise of the permanent magnet generator with demagnetization faults, a 1.5 MW permanent magnet synchronous generator (PMSG) with 32 poles and 4 branches in parallel and fractional slot is investigated. The three dimensional thermal-field finite element and mathematical models of PMSG with no and different demagnetizations in rotor permanent magnet were established. The heat sources used in the thermal-field were obtained by a two-dimensional (2D) electromagnetic field analysis. The temperature field of the PMSG rotor was calculated with no demagnetization, single piece of permanent magnet demagnetization and the adjacent two pieces of permanent magnet demagnetization, respectively. The temperature distributions with three different conditions were compared and the influences of permanent magnet demagnetization on the temperature were analyzed. Using the same method, the temperature distribution of a 400W-10 poles permanent magnet synchronous was analyzed. The calculated temperature results were compared with the test values, which verify the correctness of the calculation method. The thermal calculation model can be applied to the thermal analysis of the other PMSGs. The research can provide diagnostic analysis basis for the PMSG with demagnetization faults.

Aiming at the problem of end structure heating caused by the excessive eddy current loss of large synchronous condensers used in ultra-high voltage (UHV) power transmission, combined with the actual operation characteristics of the synchronous condenser, a three-dimensional transient electromagnetic field physical model is established, and three schemes for adjusting the end structure of the condenser under rated condition are researched. The original structure has a copper shield and a steel clamping plate. Scheme 1 has no copper shield but has a steel clamping plate. Scheme 2 has no copper shield but has an aluminum clamping plate. By constructing a three-dimensional fluid–solid coupling heat transfer model in the end of the synchronous condenser, and giving the basic assumptions and boundary conditions, the eddy current loss of the structure calculated by the three schemes is applied to the end region of the synchronous condenser as the heat source, and the velocity distribution of the cooling medium and the temperature distribution of each structure under the three different schemes are obtained. In order to verify the rationality of the numerical analysis model and the effectiveness of the calculation method, the temperature of the inner edge of the copper shield in the end of the synchronous condenser is measured, and the temperature calculation results are consistent with the temperature measurement results, which provides a theoretical basis for the electromagnetic design, structural optimization, ventilation and cooling of the synchronous condenser.

In order to study the multiple restricted factors and parameters of the eddy current loss of generator end structures, both the multi-layer perceptron (MLP) and support vector regression (SVR) are used to study and predict the mechanism of the synergistic effect of metal shield conductivity, relative permeability of clamping plates and structural characteristics of eddy current losses. Based on the eddy current losses of generator end structures under different metal shielding thicknesses and electromagnetic properties, the calculation accuracy of the MLP and SVR is compared. The prediction method gives an effective means for the complex design of the end region of the generator, which reduces the effort of the designers. It also promotes the design efficiency of the electrical generator.

The starting and synchronization process of high-voltage permanent magnetic synchronous motors (HVPMSM) is a complex electromechanical transient problem. This paper proposes a multi-objective five-dimensional optimization method for starting characteristics of HVPMSM based on quadratic response surface models (QRSM) combined with Cuckoo search algorithm. Eighty-nine sets of transient finite element models were developed. To obtain starting current, starting time, starting torque and torque ripple, the transient process of HVPMSM is calculated with different cage bar width, cage bar depth, cage bar conductivity, and slot wedge conductivity. Steady-state and locked rotor experiments are conducted to verify the accuracy of the FEA. Then, the Cuckoo search method is employed to optimize design parameters achieved by the finite element models to obtain the minimum starting current, the maximum starting torque, the shortest starting time, and the minimum torque ripple, while maintaining high output performance and low cost. The results demonstrate that QRSM combined with Cuckoo search algorithm accurately describe the non-linear relationship between the structural characteristics, material properties and output performance of the HVPMSM. The best solutions are consistent with the results of the finite element analysis. In addition, the theoretical method is verified by experiments.

Electromagnetic and heat issues are more complex in the end region of a generator than in the line segment area. In this study, the electromagnetic field and related challenges are discussed. Stepped cores are considered in the performed calculations. Eddy-current losses variation mechanisms for structures in the end region and iron losses of end stepped cores are investigated under rated load condition, using space vectors. The effects of the end windings stretching out the end cores from the rotor and stator on the electromagnetic losses of the end structures studied in detail. The obtained results can be employed for developing large turbo-generators, and reveal a novel approach for reducing eddy currents and iron losses.

The electromagnetic and heat issue is the core of the key problems for large synchronous generators. This paper presents a new method to account for the rotary excitation field of a large synchronous generator using a new 3-D static frequency-domain finite element to solve the end magnetic field and electromagnetic losses via phase transformation. The solution time is significantly reduced. Both magnetic flux leakage and temperature testing of the end structures are conducted. There is good consistency between the theoretical simulation and the experimental results for both magnetic and thermal fields. The regularity of the magnetic and thermal field distributions is studied drawing on the electromagnetic and heat transfer theories.

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) can be improved by introducing appropriate additives into perovskite precursor solutions. However, the exact role and mechanism of additives are still unclear. In this study, self-designed cognition experiments were conducted to improve the hole extraction efficiency, as well as to deeply understand the working principle of additives. A common hole transport material, 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl) amino]-9,9′-spirobifluorene (spiro-OMeTAD), was used as an additive for bulk heterojunction PSCs (BHJ-PSCs). The results showed that the PCE of mesoporous BHJ-PSCs (M-BHJ-PSCs) was enhanced by more than 15% when an extremely low concentration of spiro-OMeTAD additive was added. However, the crystallization of the perovskite was hampered and the recombination risk increased when grain boundaries increased in the perovskite layer. Planar BHJ-PSCs were fabricated to further investigate the role of additives. In comparison with those in planar BHJ-PSCs, the hole extraction efficiency and diffusion length significantly improved in M-BHJ-PSCs due to the transport paths and relay effects caused by the spiro-OMeTAD additive. Subsequently, exact functions and a new working principle of additives in BHJ-PSCs were proposed. This study may extend the possibilities of designing highly efficient PSCs through the promotion of additive research and application.

Ship demolition is a significant source of marine pollution. Not recycled properly, toxic chemicals can be released and pose great dangers to both the environment and public health. By investigating over 22,500 scrapped vessels’ business records ranging between 2000 and 2019, we find how business owners in developed countries disguise ships’ true identity by registering them in developing regions with loose approaches to labor and environmental protection, thus creating a leeway to violate environmental justice. International treaties and regional regulations have failed to correct the problem. Neither the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal nor enhanced regional regulations from the European Commission are effective. We propose three reforms to make the shipping industry more sustainable.

The TiO 2 nanotube (TONT) based heterojunction photocatalyst was developed via the coupling of reduced graphene oxide (rGO) and SnO 2 :F film (FTO). Based on the characterization of Raman analysis, XRD, SEM, TEM, XPS and ESR, the crystal phase, morphology, heterojunction interfacial interaction and the photoinduced electron chemical environment of the samples are studied. In the photodegradation of methylene blue (MB) solution under UV irradiation, the rGO-TONT/FTO heterojunction photocatalyst exhibits the improved photocatalytic reaction rate, 3 times greater than that of pure TONT. The enhanced photocatalytic mechanism was discussed by PL. The effectively separate charge in heterojunction structure of rGO-TONT/FTO is responsible for the enhanced photocatalytic activity. Wherein, the abundant oxygen vacancies at TiO 2 surface and the chemically bonded interface in rGO-TONT heterojunction also contributes to the interfacial electron transfer. Besides, the introduction of rGO enhanced its optical absorption capacity.

Synchronizing out of phase may sometimes occur to a turbine generator due to the misoperation or failure of a synchronizing controller. There could be a large impulse current in stator windings during out of phase synchronizing. The impulse current could seriously damage the windings insulation, and the magnetic flux density might be easily supersaturated at the rotor pole surface, leading to stronger stress on the rotor tooth and damage the turbine generator. Aiming at studying the electromagnetic field when synchronizing out of phase occurs, a mathematical model of the transient electromagnetic field with field-circuit-grid coupled is established by taking a 150 MW air-cooled turbine generator for consideration. Impulse current in stator winding and supersaturation at the rotor pole surface are calculated respectively in different angles between the vector of the turbine generator electromotive force and voltage vector of power grid. According to the largest impulse current in stator windings at the 180° out-of-phase synchronization, the influence on the magnetic field distribution and saturation at the rotor pole surface of turbine generator stator resistance and the end region leakage inductances that vary in a certain range is studied. The results could provide theoretical basis for researching of electromagnetic field at out-of-phase synchronization of large turbine generator in the end zone.

Partially reduced graphene oxide functionalized with Fe nanoparticles alone or combined with Au and Pt nanoparticles is synthesized and characterized, and their effects on Polymer Electrolyte Membrane Fuel Cell (PEMFC) power output and carbon monoxide resistance are tested. Samples were prepared with various combinations of metal nanoparticles to create a cost-effective catalyst. Transmission and scanning electron microscopy revealed metal nanoparticles embedded on graphene sheets, some with magnetic susceptibility. PEMFC tests exhibited power output that was >180% of the control in a pure H2 gas feed and 250% of the control in a H2 gas feed with 1000 ppm of CO.

From microwave atomic clocks to light clocks, atomic or ionic clocks often rely on atom or ion trapping or manipulation technology. Trapping hydrogen (H) atoms in atomic storage bulbs (ASBs) is one of the key technologies of H atomic clocks. H atoms remain in an ASB for some time during which they undergo several relaxation processes (including spin-exchange collision relaxation, atom–wall collision relaxation, and magnetic-field inhomogeneity relaxation) and interact with the electromagnetic field within the resonant cavity in the TE011 mode, giving rise to continuous atomic transitions and self-oscillations. In this study, an optimal atomic storage time Tb for a H maser was determined by optimizing various collisional relaxation times of the atomic ensemble and reducing the width of the atomic resonance line through the continuously adjustable length and radius of the opening of an ASB at various atomic beam intensities ξ (which is the number of atoms in the atomic beam), namely, 3 × 1012 atoms/s, 4 × 1012 atoms/s, and 5 × 1012 atoms/s, while keeping the structural properties and physical conditions of the H maser unchanged. For ξ = 5 × 1012 atoms/s and Tb ≈ 0.8 s, a frequency stability of 0.95 × 10−15 could be achieved at 1000 s.

Constitutional dynamic chemistry (CDC), including both dynamic covalent chemistry and dynamic noncovalent chemistry, relies on reversible formation and breakage of bonds to achieve continuous changes in constitution by reorganization of components. In this regard, CDC is considered to be an efficient and appealing strategy for selective fabrication of surface nanostructures by virtue of dynamic diversity. Although constitutional dynamics of monolayered structures has been recently demonstrated at liquid/solid interfaces, most of molecular reorganization/reaction processes were thought to be irreversible under ultrahigh vacuum (UHV) conditions where CDC is therefore a challenge to be achieved. Here, we have successfully constructed a system that presents constitutional dynamics on a solid surface based on dynamic coordination chemistry, in which selective formation of metal-organic motifs is achieved under UHV conditions. The key to making this reversible switching successful is the molecule-substrate interaction as revealed by DFT calculations.

Large turbo-generators are an important energy conversion device in power stations. Once a failure occurs in the turbo-generator, it not only affects the reliability of the power system but also causes enormous economic losses. Nowadays, large air-cooled turbo-generators have developed. The safe and steady operation of turbo-generator is important for the electric power system. Leakage magnetic field is a potential hazard in end region of a turbo-generator. Leakage magnetic flux could cause eddy current to be induced in the metal component of end region, which leads to heat generation. In this paper, aiming at the complex end structure of turbo-generator, a three dimensional (3-D) mathematic model used for electromagnetic field calculation in end region of a 150-MW air-cooled turbo-generator is established. Finite element method is used to calculate the 3-D magnetic field in end region of a turbo-generator. Magnetic flux leakage testing is conducted under noload condition. It shows that there is a good agreement between the theoretical simulation and the experimental results. Eddy current loss of end parts is gained based on the electromagnetic induction theory.

The heat loss and cooling modes of a permanent magnet synchronous motor (PMSM) directly affect the its temperature rise. The accurate evaluation and prediction of stator winding temperature is of great significance to the safety and reliability of PMSMs. In order to study the influencing factors of stator winding temperature and prevent motor insulation ageing, insulation burning, permanent magnet demagnetization and other faults caused by high stator winding temperature, we propose a computer model for PMSM temperature prediction. Ambient temperature, coolant temperature, direct-axis voltage, quadrature-axis voltage, motor speed, torque, direct-axis current, quadrature-axis current, permanent magnet surface temperature, stator yoke temperature, and stator tooth temperature are taken as the input, while the stator winding temperature is taken as the output. A deep neural network (DNN) model for PMSM temperature prediction was constructed. The experimental results showed the prediction error of the model (MAE) was 0.1515, the RMSE was 0.2368, the goodness of fit (R2) was 0.9439 and the goodness of fit between the predicted data and the measured data was high. Through comparative experiments, the prediction accuracy of the DNN model proposed in this paper was determined to be better than other models. This model can effectively predict the temperature change of stator winding, provide technical support to temperature early warning systems and ensure safe operation of PMSMs.

There is an urgent demand for producing biodegradable polymer based composites with good thermal and/or electrical conductivity to mitigate the plastic pollution introduced by electronic waste. Here, we have designed and engineered a mechanically strong, melt processable, biodegradable polymer based nanocomposite with excellent thermal and electrical conductivity using filler dispersion principle and the work of adhesion ( W a ) as guides. In the design, graphene nano-platelets (GNPs) were dispersed into a highly ductile biodegradable polymer - poly (butylene adipate-co-butylene terephthalate) (PBAT). Blending with another biodegradable polymer, poly (lactic acid) (PLA) that has low affinity to GNPs, confined the dispersion of GNPs within PBAT matrix, thereby facilitating the formation of a percolated network. As a result, high thermal conductivity ( 3.15 W / m ⋅ K ) and electrical conductivity ( 338 S / m ) were achieved for the nanocomposite at 40 wt% of GNPs loading, and the mechanical performance remained strong even at such filler loading due to the strong interaction between GNPs and PBAT. This study provides a new strategy for effectively producing high thermally and/or electrically conductive polymer nanocomposites.

Good conductive treatment of curved-surface piezoelectric composites could prevent failure of curved transducers, which are the core devices of many wideband and high-frequency sonar systems. A series of ratio between epoxy resin and curing agent were tested to investigate conductive treatments of curved-surface piezoelectric composites. The curved-surface piezoelectric composite was first prepared. The sample whose epoxy resin to and curing agent ratio was 100:150 showed the largest welding spot strength in many areas, but its homogeneity was not as good as samples with epoxy resin to curing agent ratio of 100:100 or 100:200. With increases in curing agent, the volume resistivities decreased, and the homogeneity became better.

Proton exchange membrane fuel cells (PEMFCs) are one of the most promising energy solutions in meeting the soaring global energy demand and relieving the environmental concerns associated with greenhouse emissions. Cost and durability are two main obstacles hindering the successful commercialization of PEMFCs. Here, we propose a solution which could significantly enhance durability, reduce PGM catalyst, and increase tolerance to impure hydrogen sources thereby reducing cost and increasing convenience by allowing operation in ambient conditions. We show that applying a coating of 1 μg/cm2 of graphene oxide (GO) directly onto the Nafion membrane or electrodes enabled a 60% enhancement of the maximum power output to 0.78 or 0.76 W/cm2, using only a total of 0.15 mg/cm2 Pt catalyst. Durability tests were carried out complying with the DOE2020 protocols, indicating that the enhancement persisted even after 30k cycles, where the maximum power decrease was only 9%, as compared with 18% in the control sample, and the decrease in voltage at 1.5 A/cm2 was only 13%, as compared with 70% of the control sample. In addition, blending of 0.1% CO gas into the input H2 stream reduced the power by 72% in the control, while only 26% power reduction was observed in the coated PEMFCs. Also, electrochemical impedance spectroscopy (EIS) measurements exhibited a decrease in resistance of only 13%, while the active Pt surface area of the electrode with GO coating after 30k cycles was 17.5% higher than the control and the minimal DOE requirement.

Tautomerization of nucleobases may induce base mismatches resulting in the abnormal disturbance of gene replication and expression, which has therefore attracted widespread interests in many disciplines. Metal atoms participating in a variety of important biological processes are found to be able to affect the nucleobase tautomerization as evidenced by many theoretical and spectroscopic studies. To get the real-space evidence and to unravel the underlying mechanism for the metal-induced tautomerization, especially from the keto form to the enol one, the interplay of high-resolution scanning tunneling microscopy imaging/manipulation and density functional theory (DFT) calculations has been employed. We present a process showing the Ni adatom-induced keto-enol tautomeric dehydrogenation of thymine molecules on Au(111). The key to making such a process feasible is the Ni atoms which greatly lower the energy barrier for the tautomerization from keto to enol form, which is rationalized by extensive DFT-based transition-state search calculations.

Although tautomerization may directly affect the chemical or biological properties of molecules, real-space investigation on the tautomeric behaviors of organic molecules in a larger area of molecular networks has been scarcely reported. In this paper, we choose guanine (G) molecule as a model system. From the interplay of high-resolution scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations, we have successfully achieved the tautomeric recognition, separation, and interconversion of G molecular networks (formed by two tautomeric forms G/9H and G/7H) with the aid of NaCl on the Au(111) surface in ultrahigh vacuum (UHV) conditions. Our results may serve as a prototypical system to provide important insights into tautomerization related issues, which should be intriguing to biochemistry, pharmaceutics, and other related fields.

A new approach has been proposed to evaluate the influence of the transverse edge effect of high-temperature superconducting (HTS) linear induction motor (LIM) in this paper. Taking a 3.5 kW single-sided HTS LIM for an example, the cross-flux density distributions were analyzed by analytical method. Based on results mentioned above, a new transverse coefficient was proposed to evaluate the influence of the transverse edge effect on the cross-flux density distribution. The influences of the motor configurations and parameters on the transverse coefficient were also investigated. The 3-D finite-element method was adopted to verify the accuracy of the presented analytical method.

Electrocatalysts for the oxygen reduction reaction (ORR) in acidic media are crucial in proton-exchange membrane (PEM) fuel cells and other electrochemical devices. Achieving ideal ORR activity and durability in acidic media remains a challenge. Here, we developed a new NFeCo-CNT/NC nanocomposite electrocatalyst from the highly available and recyclable plant biomass Typha orientalis using a readily scalable approach. The electrocatalyst exhibits excellent ORR activity, superior stability and tolerance to methanol poisoning effects in acidic media. The value of the onset potential and half-peak potential of the typical product is only 70 mV and 65 mV less than that of Pt/C, respectively. The NFeCo-CNT and NFeCo-NC in the nanocomposite have synergistically enhanced ORR activities. The catalyst may have practical applications in fuel cells. One of the important accomplishments of this work is the discovery that trace Fe3+ and Co2+ can synergistically catalyze the growth of the carbon nanotubes when melamine serves as the CNT precursor.

Developing an effective electrocatalyst for the oxygen reduction reaction is a momentous issue in fuel cells. In this paper, we successfully synthesized the N-doped TiO2 nanorods/graphene (N-TiO2/NG) nanocomposite, which comprise the N-doped TiO2 (N-TiO2) nanorods (40–60 nm diameter and 90–300 nm length) and self-assembled nitrogen-doped graphene (NG) networks. We found that the nanocomposite exhibits great oxygen reduction reaction (ORR) electrocatalytic performance and also shows long durability and methanol tolerance than that of the commercial 20% Pt/C catalyst. This new nanocomposite may also have potential applications in other fields, which are related to energy storage, gas sensors, photocatalysis, and so on.

Although the G-quartet structure has been extensively investigated due to its biological importance, the formation mechanism, in particular, the necessity of metal centers, of an isolated G-quartet on solid surfaces remains ambiguous. Here, by using scanning tunneling microscopy under well-controlled ultra-high-vacuum conditions and density functional theory calculations we have been able to clarify that besides the intraquartet hydrogen bonding a metal center is mandatory for the formation of an isolated G-quartet. Furthermore, by subtly perturbing the local coordination bonding schemes within the formed G-quartet complex via local nanoscale scanning tunneling microscopy manipulations, we succeed in modulating the d orbitals and the accompanying magnetic properties of the metal center. Our results demonstrate the feasibility of forming an isolated G-quartet complex on a solid surface and that the strategy of modulating electronic and magnetic properties of the metal center can be extended to other related systems such as molecular spintronics.

With increased turbogenerator capacity and electromagnetic load, overheating of the complex end parts has become one of the main problems affecting safe and stable turbogenerator operation. In this research, a flow network was built representing the structural and ventilation characteristics of a 330-MW turbogenerator. The fan inlet velocity and pressures (boundary conditions) of each end-region outlet were obtained by the flow network method. The 3-D transient electromagnetic field in the turbogenerator end was calculated, and the eddy current losses (heat sources) of the end parts were obtained by the finite-element method. To study the surface heat-transfer coefficient distribution on the stator-end winding surface, fluid and thermal mathematical and geometric models of the whole turbogenerator end region were given. Using the finite-volume method, the surface heat-transfer coefficient distribution on the complex 3-D stator-end winding surface, fluid-flow distribution, and temperature distribution of the end parts were investigated under rated-load conditions. The calculated temperature results match well with measured data. This research can provide a theoretical basis for calculating the heat-transfer coefficients of the outer surfaces of large turbogenerators.

The leading operation of large generators is an effective method to adjust the electric reactive power surplus, and the leading-power factor was restricted by the temperature rise of the end parts. In this paper, a three-dimensional (3-D) electromagnetic field of a 330-MW water-hydrogen-hydrogen-cooled turbogenerator in the end region was investigated, and the effect of end leakage magnetic flux on stator step packets was considered in the calculation process. The magnetic flux density distribution was analyzed, and the eddy current losses of metal parts in the end region and core losses of stator step packets were calculated under lagging and leading operations. The influences of the leading-power factor on the losses of end components were analyzed, which could provide a theoretical basis for the safety of the leading operation.

Nucleobase tautomerization might induce mismatch of base pairing. Metals, involved in many important biophysical processes, have been theoretically proven to be capable of affecting tautomeric equilibria and stabilities of different nucleobase tautomers. However, direct real-space evidence on demonstrating different nucleobase tautomers and further revealing the effect of metals on their tautomerization at surfaces has not been reported to date. From the interplay of high-resolution STM imaging and DFT calculations, we show for the first time that tautomerization of guanine from G/9H to G/7H is facilitated on Au(111) by heating, whereas such tautomerization process is effectively inhibited by introducing Ni atoms due to its preferential coordination at the N7 site of G/9H. These findings may help to elucidate possible influence of metals on nucleobase tautomerization and provide from a molecular level some theoretical basis on metal-based drug design.

Due to the complexity of the structures and magnetic field distribution in the end region of large turbogenerators, using a 330-MW water-hydrogen-hydrogen cooled turbogenerator as an example, the 3-D mathematical and geometry models of the nonlinear transient eddy current field were given. Taking the nonlinearity of the core material and the influences of noncontact between the copper screen and the clamping plate, as well as the shape of stator end windings into consideration, the 3-D transient electromagnetic field was calculated, and the losses of different metal parts were obtained by the finite-element method. The calculated power losses were applied to the thermal field as heat sources. Temperatures of the copper screen were gained. The calculated results of copper screen were well coincident with the test data. Hence, the calculated results are accurate, and the method of calculation is effective.

With the appearance of high-performance permanent magnet (PM) materials as well as the development of computer technology and nanotechnology and electricity machine theory, scholars have done a lot of research on the self-starting permanent magnet synchronous motor and have made many achievements. Although the starting permanent magnet synchronous motor has many advantages compared with the induction motor, there are also many problems. Since the self-starting motor needs to realise the self-starting and maintaining the synchronous speed operation, its rotor structure design is more complex. The rotor requires the starting winding and the magnets coexist, so there is 'space competition', especially the small motors with high power density. Nowadays, nano-materials are applied on a motor to improve its electromagnetic performance. In this paper, the electromagnetic performance of a PM motor with different metal nano-material bars is researched by finite element analysis (FEA). In this paper, the electromagnetic performance of a PM motor is researched when the rotor bars are with different sizes metal nano-palladium by FEA. The magnetic field distribution, the dynamic speed and torque variation and the eddy current losses are analysed respectively.

Graphene-based materials are promising for hydrogen production and storage. In this work, using density functional theory calculations, we explored how a hydroxyl group influences H 2 dissociation on graphene. Presence of the hydroxyl group makes the binding of H atom with graphene stronger, as the binding energy of H atom with the hydroxyl-modified graphene is higher than that with the pristine graphene. The para-site is the most favorable site for H 2 dissociation on both the pristine and hydroxyl-modified graphene. The energy barrier of H 2 dissociation at para-site on the pristine graphene is 3.10 eV whereas that on the hydroxyl-modified graphene is 2.46 eV, indicating a more facile H 2 dissociation on the hydroxyl-modified graphene.

Since the structure of a large capacity turbogenerator is complex in the end region, accurate calculation about the leakage magnetic field becomes a key factor in the design. In this paper, a 330-MW level turbogenerator is electromagnetically analyzed and investigated with different metal screens in the end region. Its nonlinear transient electromagnetic field and eddy current loss were calculated by using the time step finite-element method (FEM). The influences of metal screen materials on the electromagnetic field and eddy current loss were compared and analyzed. All of these will contribute to the turbogenerator engineering design. Using the loss gained by the magnetic field calculation as a heat source, the thermal field of the end region with a copper screen was calculated. Compared with the test data, the calculated temperature results match well with the measured data.

Botanical pesticides play increasingly important roles in the control of agricultural pests. In this study, the insecticidal effects, specifically the repellent action and contact toxicity, of the essential oil extracted from Chinese chive (EOC) against Plutella xylostella larvae were confirmed. The mechanisms of repellent's action were studied using electroantennograms (EAGs), and the effects on glutathione S-transferase (GST), carboxylesterase (CarE), and acetyl cholinesterase were investigated after EOC treatments. The EOC affected the EAG results and inhibited the activities of GST and CarE in treated P. xylostella larvae, which could explain its insecticidal effects. And, four pyrazines showed greater repellent activities than that of the EOC, which was confirmed as the main active compounds of EOC.

Template cations have been extensively employed in the formation, stabilization and regulation of structural polymorphism of G-quadruplex structures in vitro. However, the direct addition of salts onto solid surfaces, especially under ultra-high-vacuum (UHV) conditions, to explore the feasibility and universality of the formation of G-quartet complexes in a solventless environment has not been reported. By combining UHV-STM imaging and DFT calculations, we have shown that three different G-quartet-M (M: Na/K/Ca) complexes can be obtained on Au(111) using alkali and alkaline earth salts as reactants. We have also identified the driving forces (intra-quartet hydrogen bonding and electrostatic ionic bonding) for the formation of these complexes and quantified the interactions involved. Our results demonstrate a novel route to fabricate G-quartet-related complexes on solid surfaces, providing an alternative feasible way to bring metal elements to surfaces for constructing metal–organic systems.

Scanning tunneling microscopy (STM) manipulation techniques have proven to be a powerful method for advanced nanofabrication of artificial molecular architectures on surfaces. With increasing complexity of the studied systems, STM manipulations are then extended to more complicated structural motifs. Previously, the dissociation and construction of various motifs have been achieved, but only in a single direction. In this report, the controllable scission and seamless stitching of metal–organic clusters have been successfully achieved through STM manipulations. The system presented here includes two sorts of hierarchical interactions where coordination bonds hold the metal–organic elementary motifs while hydrogen bonds among elementary motifs are directly involved in bond breakage and re-formation. The key to making this reversible switching successful is the hydrogen bonding, which is comparatively facile to be broken for controllable scission, and, on the other hand, the directional characteristic of hydrogen bonding makes precise stitching feasible.

The first quantitative and statistical evaluation of cirrus mammatus clouds based on wavelet analysis of remote sensing data is made by analyzing the University of Utah Facility for Atmospheric Remote Sensing (FARS) 10-yr high-cloud dataset. First, a case study of cirrus mammata combining a high-resolution lidar system and a W-band Doppler radar is presented, yielding an assessment of the thermodynamic environment and dynamic mechanisms. Then, 25 cirrus mammatus cases selected from the FARS lidar dataset are used to disclose their characteristic environmental conditions, and vertical and length scales. The results show that cirrus mammata occur in the transition zone from moist (cloudy) to dry air layers with weak wind shear, which suggests that cloud-induced thermal structures play a key role in their formation. Their maximum vertical and horizontal length scales vary from 0.3 to 1.1 km and 0.5 to 8.0 km, respectively. It is also found that small-scale structures develop between the large-scale protuberances. The spectral slopes of the lidar-returned power and mean radar Doppler velocity data extracted from the cirrus cloud-base region further indicate the presence of developed three-dimensional, locally isotropic, homogeneous turbulence generated by buoyancy. Finally, comparisons of anvil and cirrus mammata are made. Although both are generated in a similar environment, cirrus mammata generally do not form fallout fronts like their anvil counterparts, and so do not have their smooth and beautiful outlines.

From the interplay of high-resolution scanning tunneling microscopy (STM) imaging/manipulation and density functional theory (DFT) calculations, we have shown that the spontaneous formation of an organometallic complex by copper–alkene interactions can be successfully achieved, where the specific molecular adsorption geometry is revealed to be the key for facilitating such interaction.

To resolve the problem of reclaiming residual heat of the flue gas for thermal organic media furnace with coal as fuel, a technique project of reclaiming residual heat of the flue gas using heat pipe technology is put forward, and the technology of heat exchanger network is optimized. 1.25MPa steam produced by the heat pipe steam generator reclaiming residual heat of the flue gas can supply supplement steam of the rapid installation steam boiler, and the boiler operation time can be reduced and the energy can be saved. The heat pipe air pre-heater further recycles residual heat of the flue gas, preheating up the air from the normal temperature to 130°C or so, as heating furnace's oxidizing air. And the efficiency of heating furnace can be improved. The project application example indicated that the economic benefit of the system of reclaiming residual heat of the flue gas using heat pipe technology is the more remarkable than that of the traditional tube-shell air pre-heater.

Various types of defect may be formed in girth welds of long-distance pipeline in the process of welding. They are hidden dangers to pipeline transportation safety. Currently, ultrasonic phased array instrument is commonly adopted for quick automatic positioning and quantitative analysis of flaws in the girth weld after welding. But as for qualitative analysis – flaw classification, traditional manual identification method is still used. By traditional method, human-made error is easily introduced and classification result is depended on the detection experiences of the inspecting person. To overcome these deficiencies, a new method combined second generation wavelet transform (SGWT) with Radial Basis Function neural network (RBFN) is proposed in this paper, realizing automatic flaw classification and reducing human factors impaction. SGWT is ideally matched local characteristics of the flaw signal, improving both the computational speed and flaw classification efficiency. Then, based on the “energy-status” feature extraction method and the above SGWT analysis, feature eigenvectors of the flaw signals are extracted, training the following RBFN. And then when the feature of any flaw is extracted, it can be recognized by the network. The output of the network is the type of the input flaw signal, realizing automatic flaw classification. Finally, an ultrasonic phased array inspection system is described. The system is integrated with automatic flaw detection and classification. Experiments are tested on a long-distance pipeline girth weld block with artificial defects in it. The results validate that the proposed method is efficient, which is helpful to increasing inspection speed and reliability of flaw inspection for long-distance pipeline girth welds.Copyright © 2008 by ASME

Static pressure method and dynamic pressure method were commonly used in pipeline leak detection. Advantages and disadvantages of the two methods were analyzed and a dynamic pressure sensor was designed for long-range oil and gas transmission pipeline. In order to improve its performance, experiments of circuit simulation was carried out on the main part of the sensor. Application experiments show that the dynamic pressure sensor is more suitable for pipeline leak detection on occasion that internal pressure changes rapidly, and contribute to increase positioning accuracy.

A new distributed optical fiber pipeline leakage pre-warning system based on the principle of Mach-Zehnder optical fiber interferometer and the method of its signal analysis are proposed in this paper. In this pre-warning system, an optical cable is laid in parallel with the pipeline in the same ditch and three single mode optical fibers in the optical cable build up the distributed micro-vibrant measuring sensor. Leakage and other abnormal events can be detected by the sensor in real-time and can be identified by using an “energy-pattern” method based on the wavelet packet analysis. The position of the leak point can be obtained by calculating the value of time delay of the two measuring signals through a correlation algorithm. This system detects various oil and gas pipeline leakages, and is especially suited for micro-leakage. At the end of this paper, experimental data obtained on oil field and the result of the signal analysis are presented. The data and the result of the signal analysis show that the measuring sensitivity and location precision of detecting leakage are improved when this technology is adopted, and abnormal events can be efficiently identified.

Due to large repair workload and cost, the detection of coating has a great guidance to a major overhaul of buried pipelines. Direct current voltage gradient (DCVG) and close interval potential survey (CIPS) techniques have already been widely used in this area and the theories are introduced in this paper. Based on the above two detection principles, a set of detection instrument for coating defects of buried pipelines is developed, and the detailed hardware and software designs of the instrument is also provided. In this instrument, pipe/soil potential is used to detect coating defects and IR drop (the product of soil current and resistance) is eliminated during potential measurement using instantaneous CP (cathode protection) current cut method. The detection results saved in Flash can be displayed on LCD of the instrument or transferred to the computer for graph plotting. Through the field application examples, it is indicated that the device designed in this article has a very high precision in defects positioning and a broad prospect of application.Copyright © 2006 by ASME

[1] The Cross-Track Infrared Sounder (CrIS) is a Fourier Transform Michelson interferometer instrument launched on board the Suomi National Polar-Orbiting Partnership (Suomi NPP) satellite on 28 October 2011. CrIS provides measurements of Earth view interferograms in three infrared spectral bands at 30 cross-track positions, each with a 3 × 3 array of field of views. The CrIS ground processing software transforms the measured interferograms into calibrated and geolocated spectra in the form of Sensor Data Records (SDRs) that cover spectral bands from 650 to 1095 cm−1, 1210 to 1750 cm−1, and 2155 to 2550 cm−1 with spectral resolutions of 0.625 cm−1, 1.25 cm−1, and 2.5 cm−1, respectively. During the time since launch a team of subject matter experts from government, academia, and industry has been engaged in postlaunch CrIS calibration and validation activities. The CrIS SDR product is defined by three validation stages: Beta, Provisional, and Validated. The product reached Beta and Provisional validation stages on 19 April 2012 and 31 January 2013, respectively. For Beta and Provisional SDR data, the estimated absolute spectral calibration uncertainty is less than 3 ppm in the long-wave and midwave bands, and the estimated 3 sigma radiometric uncertainty for all Earth scenes is less than 0.3 K in the long-wave band and less than 0.2 K in the midwave and short-wave bands. The geolocation uncertainty for near nadir pixels is less than 0.4 km in the cross-track and in-track directions.

Aiming at providing a theoretical basis for the 1000-MW giant fully air-cooled hydrogenerator, which is being studied and developed currently, this paper established a coupling calculation model of 3-D fluid and temperature field based on the actual structure and size of a 250-MW fully air-cooled fanless hydrogenerator. Fluid dynamics control equations, and corresponding boundary conditions in the solved region were given. The additional losses from electromagnetic field calculation were applied to the coupling model as heat sources. Using a computational fluid dynamics approach, the flow distribution of cooling air and the temperature distribution of rotor structures were obtained. It focused on the axial and radial variation rules of the flow condition of cooling air between adjacent poles. Meanwhile, it conducted a detailed research study on the variation rule of the heat-transfer coefficients of pole shoes and damping bars. Temperature calculated value of exciting windings was coincident well with the measured value. The calculated error between the two values meets the engineering requirement, thus verifying both applicability and accuracy of the solution method this paper presents.