489 research outputs found
Investigation of lithium transport through an electrodeposited vanadium pentoxide film electrode
No full textKinetics of Double-Layer Charging/Discharging of the Activated Carbon Fiber Cloth Electrode - Effects of Pore Length Distribution and Solution Resistance
No full textElectrophoretic deposition of Ni nano-particles for self-repairing of heat exchanger tubes
No full textNonlinear Ultrasonic Inspection of the Effect of Contaminants on Material Properties of Epoxy-Adhesive
No full textAdhesive joints have been an effective alternative to conventional mechanical fasteners for joining materials in the aerospace and automotive industries. Although adhesive joints have various advantages, including uniform stress distribution, lower weight, improved corrosion tolerance, and design flexibility, there can be various defects in adhesive joints, which have limited wider application. This paper investigates the effect of a contaminant on the chemical and mechanical properties of the epoxy-adhesive and seeks to determine if a SHG method can reliably detect and characterize the degree of contamination in the epoxy-adhesive. A contract based ultrasonic through-transmission method was used to measure nonlinearity and then the nonlinearity parameter was calculated using the measured fundamental and second harmonic frequency components in the signals. It was found that there is higher sensitivity to contaminant concentration, up to 1.5%, of the nonlinearity parameter than that for the sound velocity. These data were also found to correlate with changes in the mechanical hardness, which was measured by the Rockwell hardness testing, with different four levels of contamination. Differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) were also conducted to assess the effect of the contaminant on thermal properties of the epoxy-adhesive. The DSC and TGA techniques were used to evaluate the curing reaction and the thermal stability of the epoxy-adhesive respectively.This is a preprint from Pyun, Do-Kyung, Lucas W. Koester, Daniel J. Barnard, and Leonard J. Bond. "Nonlinear ultrasonic inspection of the effect of contaminants on material properties of 2." Ultrasonics 35, no. 8 (1998): 573-580. doi: https://doi.org/10.21203/rs.3.rs-1502609/v1 Published as Pyun, Do-Kyung, Lucas W. Koester, Daniel J. Barnard, and Leonard J. Bond. "Nonlinear ultrasonic inspection of the effect of contaminants on material properties of epoxy-adhesive." Journal of Nondestructive Evaluation 41, no. 4 (2022): 75. doi: https://doi.org/10.1007/s10921-022-00904-y
Nondestructive characterization of contaminant-induced material softening in epoxy polymers using nonlinear ultrasonic measurements
No full textEpoxy polymer-based materials are widely used in structural assemblies due to their efficient and robust bonding capabilities. Nondestructive testing tools are needed to assess joint quality, and ideally strength, as contaminants, and some other defects, introduced during the manufacturing process can potentially cause material softening of the epoxy, leading to the degradation of the structural integrity of the bonded components. The application of the nonlinear response with ultrasonic methods used to characterize the epoxy material itself has been underexplored. This study investigates the use of an ultrasonic second-harmonic generation (SHG) method to characterize contaminant-induced material softening in epoxy polymers, with the contaminant being a release agent. The nonlinearity parameter associated with SHG was measured with varying contamination levels. To validate the effectiveness of the SHG method, nonlinear resonant ultrasonic spectroscopy (NRUS) was employed to independently assess the variation in material softening with the increase of contamination levels. Additionally, tensile testing was conducted on contaminated samples to establish a correlation between mechanical strength and the nonlinear parameter related to the degradation due to the material softening. This study demonstrated that the SHG technique is a promising nondestructive evaluation method for detecting contaminant-induced degradation in epoxy materials.This is a manuscript of an article published as Pyun, Do-Kyung, Daniel J. Barnard, and Leonard J. Bond. "Nondestructive characterization of contaminant-induced material softening in epoxy polymers using nonlinear ultrasonic measurements." NDT & E International (2025): 103364. doi: https://doi.org/10.1016/j.ndteint.2025.103364
An integrated hybrid device for binary-phase-shift-keying subcarrier modulation
No full textWe propose an integrated optical/radio frequency (RF) hybrid device for binary-phase-shift-keying subcarrier modulation that is based on optical amplitude modulation and interference with phase delay. The device consists of two multiple-quantum-well (MQW) electroabsorption (EA) modulators branched with two multimode interference (MMI) couplers. When an RF carrier was applied to one modulator and a digital signal to the other one, the phase modulation of the RF subcarrier was realized.This work was supported in part
by the Korea Science and Engineering Foundation (KOSEF) through the Opto-
Electronics Research Center (OERC-99-0809-02-02) at the Korea Advanced
Institute of Science and Technology (KAIST) and the Ministry of Information
and Communications at ETRI
Optical BPSK subcarrier modulation using integrated hybrid device
No full textAn integrated optical/RF hybrid device has been designed and fabricated for binary-phase-shift-keying subcarrier modulation. The device has been used to directly modulate an RF subcarrier of 10GHz in a BPSK scheme with an independently applied RF carrier and digital signal
Optical binary-phase-shift-keying modulation of 10 GHz using an integrated hybrid device
No full textAn integrated optical/RF hybrid device was designed and fabricated for binary-phase-shift-keying (BPSK) subcarrier modulation. The device is composed of two identical high-speed multiple quantum well electroabsorption modulators branched with two multimode interference couplers. Using the device, we demonstrated that a RF subcarrier of 10 GI-Iz is directly modulated in a BPSK scheme with an independently applied RT carrier and digital signal.This study was partially supported by the Ministry of the Information and Communications of ETRI
Comments on the review ‘Anomalous behaviour of hydrogen extraction from hydride-forming metals and alloys under impermeable boundary conditions', by J.-W. Lee, S.-I. Pyun, Electrochim. Acta 50 (2005) 1777-1805
No full textInternational audienceThe review by Lee and Pyun, which was published recently [Electrochim. Acta 50 (2005) 1777-1805], provides a comprehensive survey of the anomalous behaviours of hydrogen transport in hydride-forming electrodes, with particular emphasis on hydrogen extraction under the impermeable boundary condition during potentiostatic current transients. Some theoretical derivations presented in the above review, as well as the validity domains of theoretical results obtained by Lee and Pyun are discussed in these comments in terms of potential step amplitude, interfacial reaction mechanism, electrode kinetics and influence of Ohmic drop. In particular, the concepts of ‘constraint by constant concentration', ‘constraint by Butler-Volmer behaviour' and ‘constraint by hydrogen transfer of absorbed state to adsorbed state' used by Lee and Pyun to discriminate between the boundary conditions at the electrode surface during hydrogen extraction are examined thoroughly in these comments. The ‘transition of the boundary condition at the electrode surface during hydrogen extraction' is also discussed, as well as the influence of Ohmic potential drop on the chronoamperometric responses to large-potential steps
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