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Aircraft electrification is one of technological innovations to achieve the goal of CO2 emission reduction in civil aviation. In present research, we focus ourselves on an Electric Fuel Metering System (EFMS). Aircraft systems are commonly expected to make not only simplified configuration and improvement of controllability, but also safety and reliability. The electrification of fuel system also requires the similar approach. Therefore, a simple and reliable redundancy concept is a crucial challenge. In addition, stable and responsive controllability that does not affect engine operation is required, especially in fuel system, it is desired to achieve both accurate metering and short settling time without overshoot or undershoot. However, in such a system, the response is nonlinear due to the fuel flow circuit and the motor drive during current limiting. Systemizing a control design that takes these constraints into considerations and that satisfies the requirements over a large dynamic range, has not been discussed. This paper discusses a design methodology to achieve optimal fuel flow control in the EFMS with redundant electric fuel pumps, considering motor current limitation by current limiters. The flow control model is created by adding the flow command increment limiter estimated as equivalent to the current limiter. Using this model, the gain characteristic map is derived analytically. The control system is extended to an active-active control redundant system. The compensating action of that system ensures that if one of the fuel pumps suddenly shut down, the remaining fuel pumps will autonomously increase their flows to maintain the required flow for the engine fuel burn.

Doxorubicin (Dox), an anthracycline antibiotic, is an anticancer drug that inhibits DNA replication and cellular metabolic processes in cancer cells with high proliferative potential. However, Dox causes severe side effects, including myocardial damage and heart failure, but the molecular mechanism underlying Dox-induced myocardial injury remains uncertain. In the present study, we evaluated the effects of Dox on the mitochondrial quality control system and regulation of mitochondrial respiration and autophagy in an in vitro rat myoblast H9c2 cell culture model using western blotting, immunohistochemistry, the Seahorse XF24 system, and flow cytometry. Our results showed that Dox did not impair the initiation of autophagic flux or the functions of lysosomes; however, Dox affected the mitochondrial quality control system, leading to a fission-dominant morphology and impaired regulation of mitochondrial respiration, thereby increasing oxidative stress and inhibited progression of autophagy, particularly the fusion of autophagosomes with lysosomes. This inhibition caused a significant decrease in the formation of autolysosomes and was responsible for the accumulation of dysfunctional mitochondria and subsequent increase in oxidative stress, eventually leading to increased myocardial cell death.

This study reports a simple method for fabricating metallic nanocoil (NC) networks at low temperatures. The fabrication process is driven by the release of inhomogeneous intrinsic stress from thin metal coatings deposited on resin nanofibers. Plasma etching was employed to degrade the resin nanofibers, thereby releasing the stress and spontaneously bending the metal coating into a helical shape through a permanent deformation. To the best of our knowledge, this is the first study that uses plasma etching for inducing stress release to form 3D helical nanostructures. Herein, Ag NCs, which are sensitive to thermal damage, were successfully fabricated. The NCs have unique structures with symmetrical left- and right-handed helical segments. The coil diameter can be controlled by adjusting the plasma etching time and power output of the plasma discharge. The proposed method is versatile, controllable, and energy efficient. Most importantly, it can be conducted at low temperatures, which is crucial for fabricating NCs that are sensitive to thermal damage.

One-dimensional Ag nanostructure-based networks have garnered significant attention as next-generation transparent conductive materials. Ag nanofibers (NFs) with high aspect ratios decrease the number density required for percolation; hence, they form qualitatively superior transparent conductive films. This study reports a novel method for rapidly fabricating Ag NFs via Pt nanoparticle-assisted H2-free reduction of solid-state AgNO3. Our results first indicated that polymers can be a source of hydrogen gas in the presence of Pt nanoparticles; Ag NFs with aspect ratios above 105 were obtained herein by heating AgNO3-containing polymer NFs in a short period of time and in an open-air environment. Our method not only successfully reduced the amount of polymer residue often encountered in spun NFs but also created an effective self-supporting reduction system that does not require an external reducing gas supply. The obtained Ag NF networks were highly conductive and transparent. Moreover, the mechanism of Ag NF formation was investigated. We demonstrate that the proposed method exhibits a high potential for producing high yields of Ag NFs in a simple and rapid manner. Supplementary Information The online version contains supplementary material available at 10.1186/s11671-021-03549-4.

Ag nanostructure-based surface-enhanced Raman scattering (SERS) substrates tend to be oxidized and corroded by sulfides owing to their large specific surface area, resulting in severe deterioration. Contrastingly, micrometer-sized Ag structures are more chemically stable. Nevertheless, no reports exist on the utilization of Ag microstructures as SERS substrates, as they lack hot spots. Herein, for the first time, SERS is observed in helical Ag structures with coil diameters and pitches of the micrometer order. The geometry-dominated anisotropic SERS effect is investigated by controlling the shape of Ag microcoils. A new model is proposed to elucidate the mechanism of hot spot formation in Ag microcoils. The results of this study should aid efforts to develop improved SERS substrates.

Recently, we detected length-dependent electromigration (EM) behavior in Sn-58Bi (SB) solder and revealed the existence of Bi back-flow, which retards EM-induced Bi segregation and is dependent on solder length. The cause of the back-flow is attributed to an oxide layer formed on the SB solder. At present, underfill (UF) material is commonly used in flip-chip packaging as filler between chip and substrate to surround solder bumps. In this study, we quantitatively investigated the effect of UF material as a passivation layer on EM in SB solder strips. EM tests on SB solder strips with length of 50 μm, 100 μm, and 150 μm were conducted simultaneously. Some samples were coated with commercial thermosetting epoxy UF material, which acted as a passivation layer on the Cu–SB–Cu interconnections. The value of the critical product for SB solder was estimated to be 38 A/cm to 43 A/cm at 353 K to 373 K without UF coating and 59 A/cm at 373 K with UF coating. The UF material acting as a passivation layer suppressed EM-induced Bi segregation and increased the threshold current density by 37% to 55%. However, at very high current density, this effect became very slight. In addition, Bi atoms can diffuse to the anode side through the Sn phase, hence addition of microelements to the Sn phase to form obstacles, such as intermetallic compounds, may retard Bi segregation in SB solder.

Helical-structured metallic nanocoils (NCs) may have special interactions with electromagnetic waves and hence attract considerable attention. Although several fabrication methods for metallic NCs have been reported, it is still challenging to obtain a network of well-shaped metallic NCs. This paper reports a novel and simple approach to fabricate metallic NC network. We show that well-shaped Pt NCs with symmetrical left- and right-handed segments can be formed through a spontaneous progress of mechanical deformation. The mechanisms of the driving force for the self-organization, formation of helical chirality balance, and shape control are demonstrated.

On the basis of a developed test structure, electromigration (EM) tests of Sn58Bi solder strips with lengths of 50 μm, 100 μm, and 150 μm were simultaneously conducted at a current density of 27 kA/cm2 at 373 K. Length-dependent EM behavior was detected, and the mechanism is discussed. Bi atoms were segregated to the anode side more easily as the strip length increased, which resulted in the formation of a thicker Bi-rich layer or Sn-Bi mixed hillocks. The results reveal the existence of back flow that depends on the solder joint length. The back flow is most likely caused by an oxide layer formed on the Sn58Bi solder. By measuring the thicknesses of the Bi-rich layers, the Bi drift velocities were obtained. The critical length of the solder joint and the critical product of the length and the current density were estimated to be 16 μm and 43 A/cm, respectively. This observation will assist design of advanced electronic devices to anticipate EM reliability.

This study investigates the electromigration (EM) behaviors and effects of the addition elements on the formation of a Bi-rich layer in Sn58Bi-based solders including Sn58Bi (SB), Sn58Bi0.5Ag (SBA) and Sn58Bi0.5Ag0.1Cu0.07Ni0.01Ge (SBACNG) solders. The EM tests were conducted at a relatively high temperature of 373 K and at a current density of 30 kA/cm2. Although the dominant diffusing atom was Bi, hillocks were formed from Sn more easily than from Bi. The electrical resistance increased in the solder during the current stressing, and the dominant factor was attributed to the formation of a Bi-rich layer. SBACNG solder showed the highest resistance to the formation of a Bi-rich layer, followed by SBA, and then SB solder. The possible addition elements enhancing the resistance of SBACNG solder are Ag, Ni and Ge. The effects of the addition elements are summarized as follows: (1) Ag distributes in the Sn phase as Ag3Sn intermetallic compounds (IMCs) that enhance the mechanical strength of Sn; (2) Ni distribution in Bi as Ni-Bi IMCs stabilizes Bi and suppresses its migration; and (3) Ge may distribute in Bi, stabilizing Bi, or Ge exists at the phase boundaries as a precipitate that inhibits Bi migration.

Atoms constructing an interconnecting metal line in a semiconductor device are transported by electron flow in high density. This phenomenon is called electromigration, which may cause the line failure. In order to characterize the electromigration failure, a comparison study is carried out with some typical phenomena treated by fracture mechanics for thin and large structures. An example of thin structures, which have been treated by fracture mechanics, is silica opti- calfibers for communication systems. The damage growth in a metal line by electromigration is characterized in compar- ison with the crack growth in a silica optical fiber subjected to static fatigue. Also a brief comparison is made between the electromigration failure and some fracture phenomena in large structures.

An eddy current microscopy technique to evaluate the electrical conductivity of thin metallic films in a non-contact manner is reported. A narrow track formed in an approximately 100 nm thick Au film was prepared, and a Co–Cr coated magnetic tip was driven to oscillate above the track both with and without current passing through the track. Despite the absence of current, the electromagnetic interaction between the tip and the stray magnetic field from the track gave rise to a phase delay in the probe. This was due to an eddy current being induced within part of the track. Moreover, measurements of the phase change in the probe oscillation for different metallic films with thicknesses of about 100 nm found this to be proportional to the electrical conductivity of the film. Finally, the electrical conductivity of an Al film was evaluated using the eddy current microscopy technique. Copyright © 2012 John Wiley & Sons, Ltd.

This study proposes a new method of proximal-probe machining that uses a rubbing process by introducing concentrated-mass (CM) cantilevers. At the second resonance of the CM cantilever vibration, the tip site of the cantilever becomes a node of the standing deflection wave because of the sufficient inertia of the attached concentrated mass. The tip makes a cyclic motion that is tangential to the sample surface, not vertical to it, as in a tapping motion. This lateral tip motion that is selectively excited by CM cantilevers was effective for the material modification of a sample due to the friction between the tip and the sample. Imaging and nanomachining under controlled shear force were demonstrated by means of the modified cantilever and a normal atomic force microscope. We were able to write a micron-sized letter "Z" having a line width of 30-100 nm on a resin surface.

This study proposes a compact and array-type design of a mechanical amplifier for piezoelectric actuators. The amplifier emulates in-plane deformation of a specific honeycomb having bow-tie-type reentrant cells. When a multilayer piezoelectric actuator causes the elongation of a cell of the amplifier in the longitudinal direction, the cell causes expansion in the transverse direction with amplification depending on its geometry. For ease of fabrication of the amplifier, a plate having periodic patterns of two holes and a slit is proposed, in which all walls and corners of the cell are replaced with rigid links and elastic hinges, respectively. Compactness of an amplified piezoelectric actuator based on the honeycomb link mechanism is demonstrated by using prototypes of uniaxial actuators and XY stages. Furthermore, theoretical formulas are discussed, which are used in the design of the amplified actuators.

Migration of atoms is presented to be utilized for fabrication of metallic micro/nanomaterials by controlling the phenomenon. Two kinds of migration phenomena are treated; one is electromigration and the other is stress migration. In addition to the formation of micro/nanomaterials, some achievements in enhancing their functions are demonstrated. One is a technique to fabricate nanocoils from the formed Cu nanowires. The others are techniques to weld or cut the micro/nanowires by using Joule heating. Finally, regarding evaluation of mechanical and electrical properties of the micro/nanomaterials, the concentrated-mass cantilever technique in atomic force acoustic microscopy and the four-point atomic force microscope technique are shown to be powerful tools, respectively.

Concentrated-mass (CM) cantilevers previously proposed by the author have features significantly effective for atomic force acoustic microscopy (AFAM), in which sample stiffness can be detected at nano scale by a vibrating tip. CM cantilevers improve the sensitivity of the detection and simplify the dynamics then lead to success in evaluations of the elastic modulus. The present study proposed a new type of CM cantilevers based on analyses of the vibrational dynamics taking account of previously ignored factors including the lateral contact stiffness and the inertia moment of a particle attached as a CM. A rod-like particle was attached on a tip in the new type to enhance the inertia moment in addition to the translational inertia. The first two modes behaved like one-freedom models, namely translational (vertical) and rotational (lateral) motions of the attached mass and the tip. Experiments on a sapphire wafer verified that the vertical and lateral stiffness can be simultaneously evaluated without mutual interference.

Atomic force acoustic microscopy (AFAM) provides nanometre resolution images reflecting sample elasticity and a possible technique for measuring the elastic modulus of thin films and extremely narrow areas. In AFAM, the resonant frequency of a micro-cantilever equipped with a sensor tip measures the contact stiffness between tip and sample. In the case of stiff samples like metals and ceramics, AFAM exhibits significantly low sensitivity, i.e., the resonant frequency is insensitive to the contact stiffness. The proposed concentrated-mass (CM) cantilever offers a smart solution to the problem without trade-offs. The present study discusses schemes for imaging elastic heterogeneity and evaluating elastic modulus in the case of CM cantilevers. The present experiment employed a flat tip with a metallic coating, namely a Ti/Pt thin film. The adhesive strength and ductility of the coating resulted in a prolonged lifetime. Images of a Ti sheet sample acquired with so-called slope detection clearly revealed nano-grains and slip bands, which would be unachievable by topographic images. The flat tip ensures a constant contact area, rendering contact stiffness independent of the magnitude of the contact force and tip–sample adhesion force, and significantly simplifying evaluation of the elastic modulus.

Strength degradation of pristine silica optical fibers immersed in water at stress-free condition, i.e., “aging”, is believed to result form the roughness development of corroded glass surface. This study has investigated in detail the geometrical properties of the roughness development. High-resolution topography was obtained by atomic force microscopy for aged samples. Simulations of surface roughening were also conducted by means of stochastic differential equation for heterogene-ous dissolution of silica. The experiments and simulations suggested that (1) the corroded surface has self-affine geometry, where the Hurst exponent is kept to 0.85 during the roughness development, (2) the roughening is caused by fluctuations of dissolution rate of silica, and (3) the roughness increases in a power law of aging time with an exponent of 0.8. Boundary element stress analyses for the self-affine surface was also carried out to obtain a relationship between the roughness and the strength, where the surface process layer was introduced to prevent difficulties concerning on stress singularity and the stress concentration factor was adopted as a fracture parameter.

In this study, a manipulation device is developed that is able to pick up and reposition a nanomaterial. In the device, the gripper, composed of two silicon microcantilevers, is actuated by XYZ stages on a rotational stage and has eight degrees of freedom. One of the microcantilevers can be vibrated at a resonant frequency by an acoustic oscillator mounted on the gripper base. We successfully picked up a copper (II) oxide NW grown on a substrate and then repositioned the NW. During the picking-up process, the NW was statically bent to break at the root by the gripper motion, or cyclically bent using the acoustic oscillator to induce a fatigue fracture. During the repositioning process, natural adhesion between the NW and the gripping surface often presented a challenge when removing the NW. This difficulty was overcome by vibrating the gripping surface, which resulted in the reduction of the adhesion effects. The mechanism of the reduction of the adhesion effects is discussed concerning the relationship between the adhesion energy and the peeling force acting on the NW. Another technique of repositioning using an inertia force generated by the oscillator is also discussed.

The resonance frequency of a micro-cantilever employed in atomic force microscopy (AFM) is expected to be a measure of tip-sample contact stiffness representing the elastic properties of a sample. Quantitative evaluation of the elastic properties from measurements of resonance frequency is difficult, however, because contact stiffness is influenced by adhesion energy as well as elastic properties. In this study, we propose a new method of evaluating these properties quantitatively from the nonlinear response of AFM cantilever vibrations. The nonlinear vibrations are easily excited due to the non-linearity in the tip-sample interaction. To simplify the formulas derived for evaluation of contact stiffness and adhesion, we focus on the case of perfect contact, where the tip is always in contact with the sample surface. The elastic properties and the adhesion energy are separated by finding the optimal set of values which minimizes the difference between the theoretical and empirical relationship of resonance frequency versus amplitude.

The maximum stress in optical glass fibers subjected to two-point bending was evaluated by E. Suhir, “Effect of the Nonlinear Behavior of the Material on Two-Point Bending of Optical Glass Fibers,” ASME Journal of Electronic Packaging, Vol. 114, pp. 246–250, taking into account the shift in the neutral axis due to the nonlinear stress-strain relationship of the materials. However, the resulting distribution of bending stress on the fiber cross-section is not realistic because it produces a nonzero axial force. In the present study, we derive the correct formulas for evaluating the maximum stress under the valid condition that the bending stress does not contribute to the axial force. Moreover, we employ the nonlinear stress-strain relationship containing a third-order term of strain, which is more appropriate for the materials than that utilized by Suhir.