Eccentric Core Research Articles

Metal@SiO2 Core-Shells with Self-Arrested Migrating Core.

Developing easy and customizable strategies for the directional structure modulation of multicomponent nanosystems to influence and optimize their properties are a paramount but challenging task in nanoscience. Here, we demonstrate highly controlled eccentric off-center positioning of metal-core in metal@silica core-shells by utilizing an in situ generated biphasic silica-based intraparticle solid-solid interface. In the synthetic strategy, by including Ca2+-ions in silica-shell and successive oxidative and reductive annealing at high temperature, a unique hairline-biphasic interface is evolved via the heat-induced concentric radial segregation of calcium silicate phase at the interior and normal silica phase at the exterior of core-shell, which can effectively arrest the outwardly migrating metal-core within rubbery calcium silicate phase, affording various eccentric core-shells, where core-positions are flexibly controlled by the annealing time and amounts of initially added Ca2+-ions. In the structure-property correlation study, the strategy allows fine-tuning of dipolar interaction-based blocking temperatures and magnetic anisotropies of different eccentric core-shells as the function of variable off-center distance of magnetic core without changing the overall size of nanoparticles. This work demonstrates the discovery and potential application of biphasic solid-solid media interface in controlling the heat-induced migration of metal nanocrystals and opens the avenues for exploiting the rarely studied high-temperature solid-state nanocrystal conversion chemistry and migratory behavior for directional nanostructure engineering.

The influence of abruptly variable cross-section on oil core eccentricity and flow characteristics during viscous oil-water horizontal flow

• New experimental data on singular pressure drop and loss coefficient are presented. • Flow pattern maps are developed for downstream pipes of sudden expansions. • Eccentric core is observed at downstream of sudden expansion. • A new phase holdup correlation was suggested, considering the effect of core eccentricity.

Resonant Transmission Line Method for Unconventional Fibers

We provide a very general review of the resonant transmission line method for optical fiber problems. The method has been found to work seamlessly for a variety of difficult problems including elliptical and eccentric core fibers as well as “holey” photonic crystal fibers. This new version has been shown to offer great versatility with respect to cases of unconventional, inhomogeneous index profiles.

A Novel Mach-Zehnder Interferometer Using Eccentric-Core Fiber Design for Optical Coherence Tomography.

A novel Mach-Zehnder interferometer using eccentric-core fiber (ECF) design for optical coherence tomography (OCT) is proposed and demonstrated. Instead of the commercial single-mode fiber (SMF), the ECF is used as one interference arm of the implementation. Because of the offset location of the eccentric core, it is sensitive to directional bending and the optical path difference (OPD) of two interference arms can be adjusted with high precision. The birefringence of ECF is calculated and experimentally measured, which demonstrates the polarization sensitivity of the ECF proposed in the paper is similar to that of SMF. Such a structure can replace the reference optical delay line to form an all-fiber passive device. A mirror is used as a sample for analyzing the ECF bending responses of the system. Besides, four pieces of overlapping glass slides as sample are experimentally measured as well.

Phase-Shifted Eccentric Core Fiber Bragg Grating Fabricated by Electric Arc Discharge for Directional Bending Measurement.

A phase-shifted eccentric core fiber Bragg grating (PS-ECFBG) fabricated by electric arc discharge (EAD) is presented and demonstrated. It is composed of a fraction of eccentric core fiber fusion spliced in between two pieces of commercial single mode fibers, where a PS-FBG was written. The EAD in this work could flexibly change the amount of phase-shift by changing the discharge number or discharge duration. Because of the offset location of the eccentric core and the ultra-narrow resonant peak of the PS-ECFBG, it has a higher accuracy for measuring the directional bend. The elongation and compression of the eccentric core keep the magnitude of phase shift still unchanged during the bending process. The bending sensitivities of the PS-ECFBG at two opposite most sensitive directions are 57.4 pm/m−1 and −51.5 pm/m−1, respectively. Besides, the PS-ECFBG has the potential to be a tunable narrow bandpass filter, which has a wider bi-directional adjustable range because of the bending responses. The strain and temperature sensitivities of the PS-ECFBG are experimentally measured as well, which are 0.70 pm/με and 8.85 pm/°C, respectively.

Rational design of Fe3O4@C nanoparticles for simultaneous bimodal imaging and chemo-photothermal therapy in vitro and in vivo.

We report a facile strategy to fabricate well-dispersed Fe3O4@C eccentric core-shell nanoparticles (NPs). The resulting Fe3O4@C eccentric core-shell NPs possess a high payload of doxorubicin (DOX) for use as synergetic pH/near-infrared (NIR)-sensitive drug delivery vehicles, and were applied for dual-modal magnetic resonance imaging (MRI)/photoacoustic imaging (PAI) and synergistic photothermal cancer therapy in vitro and in vivo.

An Integrated Fiber Michelson Interferometer Based on Twin-Core and Side-Hole Fibers for Multiparameter Sensing

An integrated fiber Michelson interferometer (MI) based on an asymmetrical twin-core fiber (TCF) cascaded with a side-hole fiber (SHF) for multiparameter sensing is proposed and demonstrated. The asymmetrical TCF consists of a centric core and an eccentric core with same refractive index. The centric core of the TCF is aligned with the core of the SHF and the eccentric core is aligned with one air hole of the SHF. Because the eccentric core of the TCF is off the axis of the fiber, a bend or twist will cause a variation of the optical path difference of the MI, which makes the MI structure be suitable for twist and vector curvature measurements. Experimental results show that the bending sensitivities of the sensor are −6.968 and 6.978 nm/m−1 at the bending directions of 0° and 180° in the curvature ranges of 0–10.708 m−1, respectively, and the twist sensitivity of the sensor is 0.639 nm/(rad/m) in the twist ranges of 0–7.44 rad/m. The structure is also sensitive to strain and temperature, and the strain and temperature sensitivities of the interferometer are 1.36 pm/ ${{\mu \varepsilon }}$ and 10.37 pm/°C, respectively.

Linear Solution for Liquid Sloshing in an Upright Elliptical Cylindrical Container with an Eccentric Core Barrel

AbstractA three-dimensional hydrodynamic analysis founded on the linear water wave theory and separation of variables in elliptical coordinates is undertaken to investigate the free sloshing charac...

Water-lubricated transport of high-viscosity oil in horizontal pipes: The water holdup and pressure gradient

This paper has investigated the water holdup and the pressure gradient of water-lubricated transport of high-viscosity oil flow in horizontal pipes. Experimental results on the water holdup and the pressure gradient of water-lubricated high-viscosity oil two-phase flow in a horizontal 1 in. pipe were discussed. Models for the prediction of the water holdup and/or the pressure gradient of core flow or water-lubricated flow were reviewed and evaluated. It was found that the water holdup of the water-lubricated flow is not only closely related to the input water volume fraction but also the degree of the oil phase eccentricity which is attributed to the oil phase Froude number. This can explain the inconsistency of the experimental results with regard to the relationship between the water holdup and the input water volume fraction in the literature. The applicability of the existing empirical or mechanistic models of water-lubricated high-viscosity oil flow were discussed and demonstrated. A modified correlation to the water holdup correlation of Arney et al. (1993) which was shown to be exclusively applicable for concentric core flow was introduced for stable water-lubricated flow, including both concentric and eccentric core flows. This correlation was evaluated and a fair applicability was shown. The accuracy of different models for the prediction of the pressure gradient of water-lubricated transport of high-viscosity oil was demonstrated to be not high in general. This is closely associated with the difficulty in accurately accounting for the influence of oil fouling on the pressure gradient.

Single hole twin eccentric core fiber sensor based on anti-resonant effect combined with inline Mach-Zehnder interferometer

A novel fiber curvature sensor without temperature cross interference based on a single hole twin eccentric core fiber has been proposed. Anti-resonant mechanism combined with inline Mach-Zehnder interference (MZI) structure are applied to the measurands detection. The spectrum is composed of a comb spectrum caused by the inline MZI and several dominant resonant wavelengths induced by anti-resonant effect. The curvature sensitivity of -1.54dB/m-1 can be achieved by intensity demodulation of the selected dip of Gaussian fitting. Similarly, the temperature sensitivity of 70.71pm/°C and 34.17pm/°C are respectively achieved by tracking coherent decrease point obtained by the FFT band pass filter method and Gaussian fit dip. Consequently, a relatively higher resolution of temperature measurement can be realized by the two methods mentioned above. The proposed sensor has a great potential for structural health monitoring, such as buildings, towers, bridges, and many other infrastructures due to its compact structure, easy fabrication and without cross impacts.

Experimental investigations and phase-field simulations of triple-phase-separation kinetics within liquid ternary Co-Cu-Pb immiscible alloys.

The phase-separation kinetics and microstructure evolution mechanisms of liquid ternary Co_{43}Cu_{40}Pb_{17} immiscible alloys are investigated by both the drop tube technique and phase-field method. Two successive phase separations take place during droplet falling and lead to the formation of a three-phase three-layer core-shell structure composed of a Co-rich core, a Cu-rich middle layer, and a Pb-rich shell. The Pb-rich shell becomes more and more conspicuous as droplet diameter decreases. Meanwhile, the Co-rich core center gradually moves away from the core-shell center. Theoretical analyses show that a larger temperature gradient inside a smaller alloy droplet induces the accelerated growth of the surface segregation shell during triple-phase separation. The residual Stokes motion and the asymmetric Marangoni convection result in the appearance of an eccentric Co-rich core and the core deviation degree is closely related to the droplet size and initial velocity. A three-dimensional phase-field model of ternary immiscible alloys, which considers the successive phase separations under the combined effects of Marangoni convection and surface segregation, is proposed to explore the formation mechanisms of three-phase core-shell structures. The simulated core-shell morphologies are consistent with the experimental observations, which verifies the model's validity in reproducing the core-shell dynamic evolution. Numerical results reveal that the development of three-phase three-layer core-shell structures can be attributed to the primary and then secondary phase separations dominated simultaneously by Marangoni convection and surface segregation. Furthermore, the effects of droplet temperature gradient on the growth kinetics of the surface segregation shell are analyzed in the light of phase-field theory.

Misfit stresses in a composite core-shell nanowire with an eccentric parallelepipedal core subjected to one-dimensional cross dilatation eigenstrain

The boundary-value problem in the classical theory of elasticity for a core-shell nanowire with an eccentric parallelepipedal core of an arbitrary rectangular cross section is solved. The core is subjected to one-dimensional cross dilatation eigenstrain. The misfit stresses are given in a closed analytical form suitable for theoretical modeling of misfit accommodation in relevant heterostructures.

A comparison between numerical predictions and experimental results for horizontal core-annular flow with a turbulent annulus

An experimental and numerical study has been performed for oil–water core-annular flow in a horizontal pipe, with a special focus on the effect of the presence of the turbulence in the water annulus. An experimental set-up was built and the obtained experimental results were used for the validation of numerical simulations that were carried out as well. The oil density was considerably lower than the water density, which leads to a rather eccentric oil core. The numerical simulations were carried out for different time dependent, fully 3D conditions. Only when a turbulence model is applied (instead of assuming laminar flow) the agreement between the predictions and the experiments is reasonably good.

Misfit stresses in a composite core-shell nanowire with an eccentric parallelepipedal core subjected to one-dimensional cross dilatation eigenstrain

We present an analytical solution to the boundary-value problem in the classical theory of elasticity for a core-shell nanowire with an eccentric parallelepipedal core of an arbitrary rectangular cross section. The core is subjected to one-dimensional cross dilatation eigenstrain. The misfit stresses are found in a concise and transparent closed form which is convenient for practical use in theoretical modeling of misfit relaxation processes.

Shielding at a distance due to anomalous resonance**This work is supported by the Korean Ministry of Science, ICT and Future Planning through NRF grant nos. 2013R1A1A3012931 (for ML) and 2016R1A2B4014530 (for ML).

A cylindrical plasmonic structure with a concentric core exhibits an anomalous localized resonance which results in cloaking effects. Here we show that if the structure has an eccentric core, a new kind of shielding effect can happen. In contrast to conventional shielding devices, our proposed structure can block the effect of external electrical sources, even in a region which is not enclosed by any conducting materials. In fact, the shielded region is located at a distance from the device. We analytically investigate this phenomenon by using the Möbius transformation, through which an eccentric annulus is transformed into a concentric one. We also present several numerical examples.

Highly Sensitive Directional Bending Sensor Based on Eccentric Core Fiber Mach–Zehnder Modal Interferometer

A high sensitive bending sensor based on eccentric core fiber (ECF) Mach–Zehnder modal interferometer (MZI) with direction recognition ability is proposed and demonstrated. The MZI-based bending sensor is fabricated by fusion splicing a piece of ECF in between two standard single mode fibers with a small lateral core-offset. Due to the eccentric location of the core of the ECF, a bend applied on the ECF-based MZI can cause an elongation or shortening of the eccentric core, which makes the ECF-based MZI suitable for directional bending measurement. The bending characteristics are investigated experimentally within the curvature range of 0–1.11 $\text{m}^{-1}$ . The bending sensitivities of the sensor are 13.49 nm/ $\text{m}^{-1}$ at the bending direction of 0° and −18.4 nm/ $\text{m}^{-1}$ at the direction of 180° corresponding to the interference dip at the wavelength of 1553.22 nm.

Two-Axis Bending Sensor Based on Cascaded Eccentric Core Fiber Bragg Gratings

A two-axis bending sensor based on cascaded eccentric core fiber Bragg gratings (ECFBGs) is presented and demonstrated. The sensor is fabricated by independently writing two FBGs in two ECFs, which are spliced with orthogonal core-offset directions. Each ECFBG is most sensitive at the core-offset direction and insensitive at the perpendicular direction. When one ECFBG is in the state of most insensitive to bend, the other ECFBG must be in the most sensitive state. Therefore, the cascaded ECFBG structure can easily realize 2-D bending measurement. The sensor's spectral responses to the curvature at different bending directions are experimentally investigated. The maximum curvature sensitivities of the two ECFBGs are 37 and 39 pm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively, within the curvature range from 0 to 8.18 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> .

Pure Directional Bending Measurement With a Fiber Bragg Grating at the Connection Joint of Eccentric-Core and Single-Mode Fibers

A novel fiber Bragg grating (FBG) structure based on an eccentric core fiber (ECF) and a single-mode fiber (SMF) was proposed and experimentally demonstrated for distinguishing the bending effect from the axial strain effect and measuring the pure directional bending. The structure is fabricated by writing a FBG on the fusion splice junction between an ECF and a SMF. The FBG formed on the ECF-SMF junction has two different resonant peaks because of the different refractive indices of the two fibers. The peak relating to the ECF is sensitive to both directional bending and axial strain, while the peak corresponding to the SMF is only sensitive to strain. By using the unique FBG structure, one can directly know whether a bending is accompanied by an axial strain, and can obtain both the direction and curvature of the bending. Experimental results show that the bending sensitivities of the FBG in the ECF part are 49.3 and −50.3 ${\rm{pm}}/{{\rm{m}}^{ - 1}}$ at directions of 0° and 180°, respectively, and the strain sensitivities of the FBG in the ECF and SMF are 0.74 and 0.70 pm/μϵ, respectively.

Drilling of CFRP with an Electrodeposited Diamond Core Drill – Effects of Air Assistance and Tool Shape –

This research was conducted to investigate the characteristics of electrodeposited diamond core drills when used to cut CFRP.An eccentric core drill was usedto improve cutting characteristics. First of all, the cutting characteristics of a normal core drill were investigated at a few different feed rates and compared with those of a diamond coated twist drill. The effect of air assistance on chip evacuation were also investigated. The cutting forces, surface roughness profile of the hole, and tool appearance were used for evaluation. At the same feed rate, more cutting force was necessary for the normal core drill than for the twist drill. When air was blown in, the cutting forces required by the core drill decreased drastically, but delamination was evident. When air was drawn out, the cutting forces of the normal core drill were almost the same as when there was no air assistance. On the other hand, when an eccentric core drill was used, the cutting force required was lower when air was drawn out than when it was blown in. Additionally, the surface quality of the hole when air was drawn out was greater than when it was blown in. When the eccentric core drill with slits was used while air was drawn out, the cutting forces, surface quality of the hole, and tool appearance were the same as when an eccentric core drill without slits was used. However, there was little core jamming. Therefore, the eccentric core drill with slits had the longest tool life.

Forging of eccentric co-extruded Al-Mg compounds and analysis of the interface strength

Within the subproject B3 of the Collaborative Research Center 692 it has been shown that Al-Mg compounds with a good bonding quality can be produced by hydrostatic coextrusion. During processing by forging, the aluminum sleeve is thinned in areas of high strains depending on the component geometry. To solve this problem an eccentric core arrangement during co-extrusion was investigated. Based on the results of FE-simulations, the experimental validation is presented in this work. Rods with an offset of 0.25, 0.5 and 0.75 mm were produced by eccentric hydrostatic co-extrusion. Ultrasonic testing was used to evaluate the bonding quality across the entire rods. For the forging investigations the basic process Rising was chosen. The still good bonding quality after forging was examined by dye penetrant testing and optical microscopy.For an optimal stress transfer between the materials across the entire component, a sufficient bonding between the materials is essential. To evaluate the interface strength, a special bending test was developed. For the conception of the bending specimens it was required to analyze the Rising specimens geometry. These analyses were performed using a reconstruction of the geometrical data based on computer tomography (CT) investigations. The comparison with the numerically deter-mined Rising specimen geometry shows good correlation. Parametric Finite Element Analyses of the bending test were used to develop the load case and the specimen geometry. By means of iterative adaption of load application, bearing and specimen geometry parameters, an advantageous stress state and experimentally applicable configuration were found. Based on this conception, the experimental setup was configured and bending tests were performed. The interface strength was deter-mined by the calculation of the maximum interlaminar interfacial tension stress using the experimental interface failure force and the bending FE model.