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As known, the wire and arc additive manufacture technique can achieve stable process control, which is represented with periodic surface waviness, when using empirical methods or feedback control system. But it is usually a tedious work to further reduce it using trial and error method. The purpose of this paper is to unveil the formation mechanism of surface waviness and develop a method to diminish it.

Two forming mechanisms, wetting and spreading and remelting, are unveiled by cross-section observation. A discriminant is established to differentiate which mechanism is valid to dominate the forming process under the given process parameters.

Finally, a theoretical method is developed to optimize surface waviness, even forming a smooth surface by establishing a matching relation between heat input (line energy) and materials input (the ratio of wire feed speed to travel speed).

Formation mechanisms are revealed by observing cross-section morphology. A discriminant is established to differentiate which mechanism is valid to dominate the forming process under the given process parameters. A mathematical model is developed to optimize surface waviness, even forming a smooth surface through establishing a matching relation between heat input (line energy) and materials input (the ratio of wire feed speed to travel speed).

The purpose of this study is to improve the performance of AISI 430 stainless steel (430 SS) in increasing its oxidation resistance, suppressing coating spalling and cracking, sustaining appropriate conductivity and blocking Cr evaporation as an interconnect material for intermediate temperature solid oxide fuel cells; a protective co-contained coating is formed onto stainless steel via the surface alloying process and followed by thermal oxidation.

In this work, oxidation behavior of coated specimen is studied during isothermal and cyclic oxidation measurements. Moreover, the conductivity is also investigated by area specific resistance (ASR) measurement.

Co-contained spinel layer shows an outstanding performance in preventing oxidation and improving conductivity compared with uncoated specimens. The protective spinel coating also reduces the ASR for coated specimen (0.0576O cm²) as compared to the uncoated specimen (1.87296O cm²) after isothermal oxidation.

The probable mechanism of co-contained alloy converting into spinel and the spinel transfer electron is presented.

This paper aims to further develop stator permanent magnet (PM) type memory machines by providing generalized design guidelines for double-stator memory machines (DSMMs) with hybrid PMs. This paper discusses the design experience of DSMMs and presents a comparative study of radial magnetization (RM) and circumferential magnetization (CM) types.

It begins with an introduction to RM and CM operating principles and magnetization mechanisms. Then, a comparative study is conducted for one of the RM-DSMM rotor pole pairs, inner and outer stator clamping angles and low coercive force PMs thickness. Finally, the two machines’ finite element simulation performance is compared. The validity of the proposed machine structure is demonstrated.

In this paper, the double-stator structure is extended to parallel hybrid PM memory machines, and two novel DSMMs with RM and CM configurations are proposed. Two types of DSMMs have PMs and magnetizing windings on the inner stator and armature windings on the outer stator. The main difference between the two is the arrangement of PMs on the inner stator.

Conventional stator PM memory machines have geometrical space conflicts between the PM and armature windings. The proposed double-stator structure can alleviate these conflicts and increase the torque density accordingly. In addition, this paper contributes to comparing the arrangement of hybrid PMs for DSMMs.

The purpose of this paper is to find an omnidirectional robust gust response stabilization (GRS) scheme with anti-disturbance and state-limited features.

Disturbance observer and barrier Lyapunov techniques, which can, respectively, estimate the lumped disturbances of the dynamic system in real-time and ensure the middle states within some prescribed ranges according to some flight safety indexes.

In the existing literature, almost all of the GRS controllers are either only for the longitudinal dynamics or only for the latitudinal dynamics. Few studies have considered the gust response alleviation problem with omnidirectional wind disturbance and full aircraft model.

This paper proposes a fresh scheme to deal with a more holistic GRS problem; the disturbance observer based (DOB) barrier Lyapunov backstepping longitudinal controller has been put forward; DOB nonlinear dynamic inversion to handle the multi-input-multi-output lateral dynamics; and to closely connect the two loops of the latitudinal dynamics, a manipulating variable conversion method is proposed.

The purpose of this paper is to improve the surface electrical conductivity and corrosion resistance of AISI 430 stainless steel (430 SS) as bipolar plates for proton exchange membrane fuel cells (PEMFCs), a protective Nb-modified layer is formed onto stainless steel via the plasma surface diffusion alloying method. The effect of diffusion alloying time on electrochemical behavior and surface conductivity is evaluated.

In this work, the surface electrical conductivity and corrosion resistance of modified specimen are evaluated by the potentiodynamic and potentionstatic polarization tests. Moreover, the hydrophobicity is also investigated by contact angle measurement.

The Nb-modified 430 SS treated by 1.5 h (1.5Nb) presented a lower passivation current density, lower interfacial contact resistance and a higher hydrophobicity than other modified specimens. Moreover, the 1.5 Nb specimen presents a smoother surface than other modified specimens after potentionstatic polarization tests.

The effect of diffusion alloying time on electrochemical behavior, surface conductivity and hydrophobicity of modified specimen is evaluated. The probable anti-corrosion mechanism of Nb-modified specimen in simulated acid PEMFC cathode environment is presented.

The purpose of this study is to investigate the corrosion resistance of superalloys subjected to ultrasonic impact treatment (UIT). The passive film growth on the superalloys’ surface is analyzed to illustrate the corrosion mechanism.

Electrochemical tests were used to investigated the corrosion resistance of GH4738 superalloys with different UIT densities. The microstructure was compared before and after the corrosion tests. The passive film characterization was described by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) tests.

The compressive residual stress and corrosion resistance of the specimens significantly increased after UIT. The order of corrosion resistance is related to the UIT densities, i.e. 1.96 s/mm² > 1.71 s/mm² > 0.98 s/mm² > as-cast. The predominant constituents of the passive films are TiO₂, Cr₂O₃, MoO₃ and NiO. The passive film on the specimen with 1.96 s/mm² UIT density has the highest volume fraction of Cr₂O₃ and MoO₃, which is the main reason for its superior corrosion resistance.

This study provides quantitative corrosion data for GH4738 superalloys treated by ultrasonic impact. The corrosion mechanism is explained by the passive film’s characterization.

This study aims to investigate the corrosion resistance and electrochemical dissolution behavior of superalloys treated by different oxidation treatments.

Ni-based superalloys were subjected to oxidation treatment at 1000 °C for 10 h, 1150 °C for 10 h and 1200 °C for 20 h. The microstructure, electrochemical dissolution behavior, elemental distribution, as well as compactness and composition of the oxide layer, were studied.

The results show that both the thickness and the granular oxide size of the oxide layer on Ni-based superalloys increase with longer oxidation times and higher temperatures. The electrochemical dissolution efficiency of Ni-based superalloys decreases with increasing oxidation time and temperature. The reduced electrochemical dissolution efficiency observed in Ni-based superalloys oxidation-treated at 1200 °C for 20 h is primarily attributed to the thicker oxide layer, which contains the highest Cr oxide content.

The findings contribute to the advancement of recycling and utilization of Ni-based superalloy scrap.

Quantum-dot Cellular Automata (QCA) is a new nano-scale transistor-less computing model. To address the scaling limitations of complementary-metal-oxide-semiconductor technology, QCA seeks to produce general computation with better results in terms of size, switching speed, energy and fault-tolerant at the nano-scale. Currently, binary information is interpreted in this technology, relying on the distribution of the arrangement of electrons in chemical molecules. Using the coplanar topology in the design of a fault-tolerant digital comparator can improve the comparator’s performance. This paper aims to present the coplanar design of a fault-tolerant digital comparator based on the majority and inverter gate in the QCA.

As the digital comparator is one of the essential digital circuits, in the present study, a new fault-tolerant architecture is proposed for a digital comparator based on QCA. The proposed coplanar design is realized using coplanar inverters and majority gates. The QCADesigner 2.0.3 simulator is used to simulate the suggested new fault-tolerant coplanar digital comparator.

Four elements, including cell misalignment, cell missing, extra cell and cell dislocation, are evaluated and analyzed in QCADesigner 2.0.3. The outcomes of the study demonstrate that the logical function of the built circuit is accurate. In the presence of a single missed defect, this fault-tolerant digital comparator architecture will achieve 100% fault tolerance. Also, this comparator is above 90% fault-tolerant under single-cell displacement faults and is above 95% fault-tolerant under single-cell missing defects.

A novel structure for the fault-tolerant digital comparator in the QCA technology was proposed used by coplanar majority and inverter. Also, the performance metrics and obtained results establish that the coplanar design can be used in the QCA circuits to produce optimized and fault-tolerant circuits.

The purpose of this paper is to provide an understanding of principal preparation and training in China by providing a background discussion of principal preparation in a number of countries. As an illustration, it provides an overview of the curriculum used in the initial preparation of school principals at Beijing Normal University.

The paper draws mainly on writing and research from China, Australia and the USA to explore principal preparation and training in China.

In addition to providing a rich description of principal preparation in China, the paper's main findings comprise seven key challenges that confront China as it endeavours to provide quality principal preparation. These challenges include China's diversity and uneven social, cultural and educational development; limited resources in some regions throughout China; the place and importance of study tours for principal preparation; the teaching approach used to train principals; the process used for assessing principal learning during their training programs; the limited transfer of learning from the classroom to the school environment; and the timing of training for principals.

Each of the challenges arising here raises important practical implications for developers of principal training programs.

The paper paints a picture of principal preparation in China and raises a number of issues and challenges with which it continues to grapple. Of note is that China is not alone in facing some of these ongoing concerns.