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The dissolution–ionization–diffusion–deposition (DIDD) model was used for developing a corrosion–resistant stainless steel (SS) by the means of alloying and the guidelines for the process were proposed. The novel HP–13Cr–Cu SS was designed to resist corrosion in H 2 S–containing geothermal environment. The results indicated that the preferential deposition of CuS promoted the heterogeneous nucleation rate of Cr 2 O 3 , FeCr 2 O 3 , and FeS, which formed denser corrosion product layer. As a result, this alloy exhibited a low corrosion rate and a high sulfide stress cracking (SSC) resistance. The results were consistent with the theoretical calculation conducted by the DIDD model. • The DIDD model established the bridge between thermodynamics and kinetics of electrochemical corrosion. • The guidelines for designing corrosion–resistance stainless steel were proposed by means of micro–alloying. • A novel HP–13Cr–Cu SS was designed based on the DIDD model to resistant the H 2 S corrosion. • The testing results verified HP–13Cr–Cu SS gained the low corrosion rate and high SSC resistance. [ABSTRACT FROM AUTHOR]

In this paper, a voltage sensorless controller is developed for a two-switch single-phase rectifier that involves power factor correction and active pulsating power buffering without electrolytic capacitors. While a two-switch rectifier normally requires four sensed signals for control, only one current sensor is required in this proposal, thereby offering advantages such as low cost, high compactness, isolation between control and power circuits, and improved reliability. While the basic operating principle follows that of a conventional voltage sensorless controller for single-switch converters, several critical design considerations are the key to the success of the implementation which is explained in detail. The feasibilities of the controller are experimentally testified with a 100-W rectifier prototype regarding both steady state and dynamic performance. [ABSTRACT FROM AUTHOR]

Active pulsating power buffering (PPB) is an effective technique to reduce the energy storage requirement of a single-phase power-factor-correction (PFC) rectifier. Existing single-phase solutions with active PPB, however, generally suffer from high voltage stresses, leading to increased power losses as well as the need for high-voltage-rating semiconductor switches. Previous works have been focusing on two-level switching converter configurations, and thus have failed to address the high-voltage-stress problem. In this paper, a single-phase three-level flying-capacitor PFC rectifier with PPB-embedded switching is proposed. The flying capacitor not only clamps the voltage stresses of all power devices but also functions as a PPB capacitor. The operating principles, control methods, and design guidelines are detailed and the feasibility of the proposed converter is verified through a 48-W (48-V/1-A) hardware prototype. The proposed rectifier is shown to achieve nearly 50% reduction of the voltage stresses, 72% reduction of the buffering capacitor's volume, and 23.8% reduction of the magnetic core size, as compared to a state-of-the-art two-level solution recently proposed. This new approach of formulating single-phase PFC rectifiers with active PPB could dramatically boost the system's efficiency and power density whilst reducing cost. [ABSTRACT FROM AUTHOR]

A component-minimized and low-voltage-stress single-phase power factor correction rectifier without electrolytic capacitor is proposed in this paper. Component minimization is achieved by embedding an active pulsating-power-buffering (PPB) function within each switching period, such that typical add-on power electronic circuits for PPB are no longer needed. Additionally, with a three-level flying-capacitor configuration, the voltage stresses of switching devices can be reduced more than 50% as compared to existing solutions that are based on embedded PPB. The relationship between the inductance requirement and the patterns of the modulation carriers, and how it can be utilized to minimize the magnetics of the rectifier, is also discussed. A 110 W hardware prototype is designed and tested to demonstrate the feasibilities of the proposed rectifier. An input power factor of more than 0.97, peak efficiency of 95.1%, and an output voltage ripple of less than 4.3% across a wide load range have been experimentally obtained. [ABSTRACT FROM AUTHOR]

Active pulsating power buffering (PPB) function can effectively reduce the twice-line frequency energy storage requirement in a single-phase rectifier. Existing single-phase solutions with active PPB must utilize more than two active switches in their circuits. Compared with conventional single-active-switch solutions without active PPB (e.g., a boost power-factor-correction (PFC) rectifier), the cost of additional semiconductor switches and gate drive circuitry in an active PPB-based rectifier may not be justified for low-power applications. This paper presents a family of single-switch single-phase rectifier with active PPB. Taking advantage of the on-time and off-time of a single switch, the proposed rectifiers are formulated by merging two converters that are duty and frequency controlled. The steady-state characteristics of these converters are analyzed. A step-by-step design procedure is provided, and an active control method for limiting the maximum switching frequency for wide-load-range operation is presented. A 100-W prototype is built for the demonstration of the proposed single-switch rectifier concept. It is envisaged that this concept, when combined with other circuit formulation techniques, e.g., partial power processing, dc-voltage feedback, may lead to new derivatives of single-switch rectifiers with more advanced features. [ABSTRACT FROM AUTHOR]

Conventional hysteresis-modulation-based sliding-mode (SM) controller exhibits a varying switching frequency. Existing SM controllers for achieving constant-switching-frequency operation often have complicated structures and/or are less straightforward to design to meet different steady state, transient, and loading requirements. In this paper, a new direct SM voltage controller based on parabolic modulation (PM) is proposed and applied to a buck converter. The objective is to achieve constant-switching-frequency operation of a switching converter with simple control structure and good operating performance. Both theoretical study and experimental work on a buck converter show that the proposed PM-based SM control can achieve 1) constant switching frequency in the continuous-conduction mode (CCM) and quasi-constant switching frequency in the discontinuous-conduction mode (DCM) of operation, 2) inherent input-disturbances rejection and superior reference tracking performance, and 3) seamless mode transition between CCM and DCM. [ABSTRACT FROM PUBLISHER]

Starting with a brief review on the existing methods of impedance emulation, this paper addresses a general and systematic approach to programmable and reconfigurable emulation of power impedances. The proposed approach not only enables the impedance value to be programed, but also allows the characteristics (i.e., type) of the impedance to be reconfigured instantly during the operation. Based on the proposed control method, emulation of at least six types of emulated power impedances (EPI) can be easily attained. In particular, it is theoretically and practically demonstrated that the impedance characteristic can be emulated through a combination of different functions. The systematic derivation of these functions is explained. New techniques that compensate the circuit power losses are introduced. This general approach has been practically verified in several EPI. Both steady-state and dynamic performance of these EPI confirm the programmability and reconfigurability. It is envisaged that the proposed method can be applied to a range of functions, such as power filtering, energy storage, and even power conversion based on direct impedance control. [ABSTRACT FROM PUBLISHER]

Conventional single-phase power-factor-correction (PFC) rectifiers with active power decoupling capability typically require more than three active switches in their circuits. By exploring the concept of power-buffer cell, a new single-stage PFC rectifier with two active switches, one inductor and one small power-buffering capacitor is reported in this paper. The proposed converter can achieve high-power factor, wide output voltage range, and power decoupling function without using electrolytic capacitor. Additionally, an automatic power decoupling control scheme that is simple and easy to implement is proposed in this paper. The operating principle, control method, and design considerations of the proposed rectifier are also provided. A 100-W prototype with ac input voltage of 110 Vrms and a regulated dc output voltage ranging from 30 to 100 V has been successfully designed and practically tested. The experimental results show that with only a 15 μF power-buffering film capacitor, the proposed converter can achieve an input power factor of over 0.98, peak efficiency of 93.9%, and output voltage ripple of less than 3%, at 100-W output power. [ABSTRACT FROM PUBLISHER]

The dissolution-ionization-diffusion-deposition (DIDD) model is corrected by a cathodic process with the feature of complex equilibrium and deposition competition. CO 2 /H 2 S corrosion of steel is taken as an example to better understand whether the main factor controlling the corrosion is CO 2 , H 2 S or both. The preliminary assessment reveals that when the rate of nuclei is less than 10 % of the total, the corrosion is controlled by only one factor. Furthermore, the calculated results also have a good agreement with morphology and weight loss experiments. This study makes a significant contribution to promoting the application of DIDD model. • The DIDD model is corrected with a complex cathodic process and deposition competition. • When the FeCO 3 nuclei rate is less than 10 %, the corrosion is controlled by H 2 S. • When the FeS nuclei rate is less than 10 %, corrosion is controlled by CO 2 , otherwise controlled by both. • Taking CO 2 /H 2 S corrosion of 20 steel as an example to validate the corrected model. [ABSTRACT FROM AUTHOR]

Existing methods of incorporating an active filter into an AC/DC converter for eliminating electrolytic capacitors usually require extra power switches. This inevitably leads to an increased system cost and degraded energy efficiency. In this paper, a concept of active-filter integration for single-phase AC/DC converters is reported. The resultant converters can provide simultaneous functions of power factor correction, DC voltage regulation, and active power decoupling for mitigating the low-frequency DC voltage ripple, without an electrolytic capacitor and extra power switch. To complement the operation, two closed-loop voltage-ripple-based reference generation methods are developed for controlling the energy storage components to achieve active power decoupling. Both simulation and experiment have confirmed the eligibility of the proposed concept and control methods in a 210-W rectification system comprising an H-bridge converter with a half-bridge active filter. Interestingly, the end converters (Type I and Type II) can be readily available using a conventional H-bridge converter with minor hardware modification. A stable DC output with merely 1.1% ripple is realized with two 50-μF film capacitors. For the same ripple performance, a 900-μF capacitor is required in conventional converters without an active filter. Moreover, it is found out that the active-filter integration concept might even improve the efficiency performance of the end converters as compared with the original AC/DC converter without integration. [ABSTRACT FROM AUTHOR]

• The effect of temperature and CO 2 pressure on the stress corrosion cracking of HP-13Cr stainless steel was proposed. • The stress and strain concentration in pitting area was studied by finite element analysis. • A pitting-to-cracking model has been built to elucidating the initiation of stress corrosion cracking. • A "HTHP-SCC electrochemical system" was developed to conduct the electrochemistry measurement under applied stress. The stress corrosion cracking of HP-13Cr stainless steel in the geothermal environment was studied by experimental measurements and modeling calculations. The stress corrosion cracking susceptibility of HP-13Cr stainless steel increases with both temperature and CO 2 pressure, and shows a synergistic effect greater than the temperature or CO 2 pressure does singly. The fracture morphologies presented quasi-cleavage fracture characteristic in the geothermal environment. The stress corrosion cracking mechanism is dominated by the anodic process. The critical stress intensity factor for stress corrosion cracking was measured and the pitting-to-cracking process was clarified by a mechanism model. [ABSTRACT FROM AUTHOR]

• TG201 inhibitor contains Cu2+, and would acquire electrode prior to H+ to form Cu film in the process of acidizing. • The galvanic corrosion between HP-13Cr SS and Cu film could be neglected. • The failure mechanism resulted in the synergistic effect resulted from the Cu film among the process of well completion. • With the temperature and pressure increased, the corrosion rate and the synergistic effect would be enhanced obviously. TG-201 inhibitor could minimize corrosion of HP-13Cr SS in the process of live acid. Moreover, it accelerated the probability of serious corrosion of SS during the well completion. The failure mechanism of TG-201 inhibitor was investigated using surface analysis and electrochemical measurements. TG201 inhibitor contains amounts of Cu2+, which would acquire the electrons prior to H+ to form Cu film. The failure mechanism was due to the synergistic effect attributed to the Cu film. Cu film promoted the formation of the occluded cell and the changes of fluid state evoked by the increase in interfacial roughness during the well completion. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear controller is presented for regulating an emerging class of high power density, high power-conversion efficiency, and high reliability (H3) single-phase power converters featuring small buffering capacitors. The proposed controller combines the best features of input–output feedback linearization and an automatic-power-decoupling (APD) control strategy, and achieves enhanced dynamic performances as compared to existing solutions based on linear control techniques. By feedback linearization, the plant models of H3 single-phase converters are fully linearized and decoupled, and thus fast dynamics, large-signal asymptotic tracking, and global stability can be achieved with simple linear controllers. Additionally, the APD strategy further strengthens the robustness of the closed-loop system as active pulsating power buffering (of the instantaneous power difference between the ac-port and the dc-port of the converter) of basically any form can be achieved. With the proposed nonlinear controller, we are able to further exploit the potential and unlock several new features intrinsic in H3 single-phase converters, e.g., active voltage holdup function, allowing extended holdup time (comparable to existing products with large dc-link capacitors) with only a small energy storage. The general theory, design procedures, and practical considerations of the nonlinear controller are detailed. A 100-W hardware prototype is also built to demonstrate the advantages of the proposed solution. New opportunities of H3 single-phase power converters with the aid of the proposed nonlinear control are also suggested for future research. [ABSTRACT FROM AUTHOR]

Traditional control strategy for a power decoupling circuit typically involves a dedicate ripple power control loop, which makes it hard to achieve satisfied transient performance. Meanwhile, traditional single-phase ac–dc converters achieve active power decoupling function with extra power switches, which inevitably increased the cost of the system. In this paper, a controller based on automatic power decoupling concept is proposed for a dependent power decoupling circuit with no extra switches. Compared with the existing methods, the system controlled by the proposed controller has superior transient performance with simplified controller's structure. The controller parameter's design procedures will also be illustrated step by step with the help of the bode diagram. In comparison with traditional control methods, simulations and experiments verify the feasibility of the proposed control methods on the dependent power decoupling circuit. [ABSTRACT FROM AUTHOR]

Highlights • The amorphous corrosion scales formed on the surface of HP-13Cr stainless steel in extremely aggressive environment. • Cr(OH) 3 precipitation contributed to the increase of scales thickness and inhibited the precipitation of FeCO 3. • As the temperature and pressure increased, the corrosion scales changed from monolayer to double layer, and then transformed into single layer. • The corrosion scales exhibited p-type semiconductivity, and density and diffusion coefficient of acceptor increase with the increasing of temperature and pressure. Abstract The nature of corrosion scales formed on HP-13Cr stainless steel (HP-13Cr SS) in the extremely aggressive environment was investigated by means of microstructure characterization and high-temperature-high-pressure electrochemical measurements. The results of these studies indicated that the precipitation of Cr(OH) 3 is the dominating factor affecting on the formation of corrosion scales, and its effect can be categorized based on two compromising aspects. On the one hand, Cr(OH) 3 precipitation contributed to the increase of scales thickness. On the other hand, it inhibited the precipitation of FeCO 3 due to the hydrolysis of Cr3+. Because of these reasons, the corrosion scales undergo significant microstructural changes, i.e., from monolayer (95 °C/2.8 MPa) to bilayer (120 °C/3.2 MPa and 150 °C/3.6 MPa), then to single layer (180 °C/3.8 MPa). Therefore, the corrosion-resistance performance of corrosion scales decreased with increasing temperature and CO 2 pressure, wherein the decreasing pitting potential and repassivation potential accompanied with the increasing density and diffusivity of acceptor in the scales. [ABSTRACT FROM AUTHOR]

• A 45-degree elbow results in a region of low velocity, high pressure and high turbulence energy. • The change in the flow state leads to the condensation of water vapor. • The synergistic effect of electrochemical corrosion and stress corrosion evokes the incident. • Changing the structure will reduce the condensation of vapor can improve the life of pipeline. A bursting incident occurred in a 45-degree elbow of a natural gas gathering pipeline in an oilfield. The failure analysis was performed by means of corrosion morphology observation, corrosion products analysis, and computational fluid dynamics (CFD) simulations. The results showed that a radical change in the fluid state at the 45-degree elbow due to its climbing structure and formation a region of low flow velocity, high pressure and high turbulence kinetic energy, which promoted the condensation of water vapor containing CO 2. Then the corrosive water droplets flowed back under the action of gravity and accumulated at the junction between the elbow and horizontal pipeline. In such a corrosive medium, electrochemical corrosion was preferred for 20 steel. In addition, the junction of the horizontal pipe and the inclined pipe exhibits higher structural stress concentration, resulting in increased corrosion thinning. Finally, the failure of the pipeline can be attributed to the synergistic effect of electrochemical corrosion and stress accelerated corrosion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe 3 O 4 @AP-Au NPs reduced spermatogenic cells apoptotic indexes and prostate weight gain. • Fe 3 O 4 @AP-Au NPs improved the sperm percentage with total motility, normal morphology, and progressive motility and Johnsen's and Miller's criteria. • The particles are almost homo-morphic and are sized between 30 and 50 nm. In the current years, conjugated bio-nanomaterials involving magnetic core are interested as promising platform in modern generation biological composites for the treatment of several types of inflammations such as epididymo-orchitis. In this regard, we described a novel Au NPs supported apple pectin (AP) modified magnetic Fe 3 O 4 nanoparticles as a novel nano-biocomposite (Fe 3 O 4 @AP-Au NPs). The post-synthetically modified biogenic material was analyzed in details over a number of physicochemical methods like, Fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), elemental mapping, X-ray diffraction (XRD) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). In the in vivo part, we divided 80 Wistar rats into five following groups (n = 16 per group): a. Control-intact group, b. Vehicle group, c. Fe 3 O 4 @AP-Au NPs group, d. epididymo-orchitis group, and e. epididymo-orchitis/ Fe 3 O 4 @AP-Au NPs group. We assessed relative sex organs weight, body weight, germ cell apoptosis, Johnson's criteria, sperm parameters, and germ cell layers number. Acute epididymo-orchitis raised the prostate relative weight and seminal vesicles and apoptotic indexes of spermatogenic cells, also decreased the quality of sperm such as sperm concentration, normal sperm percentage, and total motility and Johnsen's and Miller's scores. Fe 3 O 4 @AP-Au NPs group reduced spermatogenic cells apoptotic indexes and prostate weight gain and improved the sperm percentage with total motility, normal morphology, and progressive motility and Johnsen's and Miller's criteria. [ABSTRACT FROM AUTHOR]

• The corrosion rate of 308L SS decreased first and then increased after the thermal-aged, thermal-aged and irradiated process. • The thermal-aged 308L SS performed a compacter and thicker passive film with the much more stable compounds. • After the thermal-aged and irradiated process, the thickness of the passive film decreased and the unstable NiOOH formed. Effect of thermal aging and irradiation on the corrosion behavior of 308L stainless steel (SS) in simulated pressurized water reactor (PWR) environment was investigated by using electrochemical techniques and surface analysis. The results delineated that the corrosion susceptibility of 308L SS decreased first and then increased obviously after the thermal-aged, thermal-aged and irradiated process, respectively. It can be attribute to variation of the microstructure and composition of the passive film. Compared with the 308L SS, the thermal-aged ones performed a compacter passive film characteristic with oxide Cr 2 O 3 , Fe 2 O 3 and hydroxide Ni(OH) 3. Whereas, after the thermal-aged and irradiated process, the thickness of the passive film decreased obviously and the hydroxide Ni(OH) 3 transform to the unstable NiOOH. As a result, performing higher corrosion susceptibility once more. [ABSTRACT FROM AUTHOR]

The influence of rare earth element (RE) Y on the microstructure and corrosion behavior of extruded AZ91 Mg alloy was surveyed via morphology characterization and corrosion performance measurements. The results indicate the corrosion resistance of the transversal section of AZ91 Mg alloy containing Y was improved compared with AZ91 Mg alloy without Y. The corrosion resistance of the longitudinal section of AZ91 Mg alloy with Y was lower than that of AZ91 Mg alloy without Y. The change of corrosion resistance can be attributed to the dispersion and volume fraction of the second phase, the effect of cathodic reduction rate, and the refined second phase. [ABSTRACT FROM AUTHOR]