Search

In the manufacturing of optical products, precise adjustments are made to maintain the optical axis alignment of optical components, which are then securely positioned using adhesives. To achieve positional accuracy at the micron level, it is essential to comprehend the deformation of the adhesive joint over time during processing. This study focuses on investigating the displacement of optical components resulting from the deformation of a cationic photopolymerized epoxy adhesive, which cures under ultraviolet (UV) radiation. First, the conversion of the adhesive was formulated based on a curing reaction model. This conversion can be divided into three stages: the initial reaction during UV irradiation, the subsequent dark reaction, and the reaction induced by heating. Moreover, formulations were developed to describe changes in curing shrinkage, thermal expansion, and viscoelasticity in relation to the conversion. These equations, governing the adhesive properties, were then used to perform finite element method (FEM) simulations to analyze the position of the optical component. Experimental tests on adhesively bonded components were conducted under conditions identical to those employed in the simulation. Throughout the curing process of the adhesive, the optical component was continuously imaged using a coherence-scanning interferometer, enabling the quantification of its displacement from the acquired images. The results of the FEM simulation and experimental analysis exhibited a consistent trend, indicating the effectiveness of the modeling and simulation methods employed in this study. The majority of the displacement of the optical component occurred over several hours during the dark reaction stage, rather than during UV irradiation. Notably, the movement of the optical component was not limited solely to the thickness direction of the adhesive layer because of curing shrinkage but also extends to the in-plane direction because of the non-uniform distribution of the UV irradiation intensity. [ABSTRACT FROM AUTHOR]

Yuichi Ono, Naohisa Miyakoshi, Yuji Kasukawa, Manabu Akagawa, Ryota Kimura, Itsuki Nagahata, Yusuke Yuasa, Chiaki Sato, Yoichi Shimada Department of Orthopedic Surgery, Akita University Graduate School of Medicine, Akita, JapanCorrespondence: Yuichi OnoDepartment of Orthopedic Surgery, Akita University Graduate School of Medicine, 1-1-1, Hondo, Akita-shi, Akita 010-8543, JapanTel +81-18-884-6148Fax +81-18-836-2617Email yuichi.ono24@gmail.comPurpose: Sarcopenia and osteoporosis are both serious health problems in postmenopausal women. The Asia Working Group for Sarcopenia recommends using the skeletal muscle index (SMI), which is height-adjusted appendicular skeletal muscle mass (ASMM). However, loss of height has been shown to be a common clinical finding in patients with osteoporosis. This study examined the prevalence of presarcopenia using height and arm span, which is a predictor of height, and investigated the diagnostic accuracy for presarcopenia.Methods: A total of 55 post-menopausal osteoporotic patients aged 62– 95 years underwent bioelectrical impedance analysis (BIA) for ASMM measurement and dual-energy X-ray absorptiometry (DXA) scan for bone mineral density (BMD). Anthropometric measurements, including height, weight, and arm span were taken, and body mass index (BMI), SMI, and arm span-adjusted SMI (Arm span SMI) were calculated. Presarcopenia was defined as SMI or Arm span SMI < 5.7 kg/m2 in this study.Results: The prevalence of presarcopenia was 27.3% and 38.2% evaluated by SMI and Arm span SMI, respectively. The prevalence of presarcopenia was higher when evaluated by Arm span SMI than by SMI. In the presarcopenia group diagnosed only by Arm span SMI (n=11), the arm span-height difference was significantly higher (p< 0.001) and the percentage of young adult mean (YAM) femoral neck-BMD was significantly lower (p=0.013) compared to the normal group diagnosed by both SMI and Arm span-SMI (n=29).Conclusion: These results indicated that Arm span SMI might be useful for the diagnosis of sarcopenia in patients with severe osteoporosis and kyphosis.Keywords: arm span, body height, osteoporosis, presarcopenia, skeletal muscle mass

In this study, the relationship between the energy release rate (G1C), crack propagation rate (da/dN), and the fracture morphology of specimens with deteriorated adhesives after moisture absorption were investigated through the double cantilever beam (DCB) method. The specimens were prepared using a thermosetting epoxy adhesive based on compound carboxyl-terminated butadiene–nitrile rubber and Al 6061-T6 adherends. To accelerate the deterioration of the adhesives, open-faced specimens were immersed in water at 63°C at varying durations. Prior to the assembly of the DCB specimens, the adherends were either treated using acidic solutions or sand blasted. Consequently, the effect of the moisture deterioration of adhesive and the surface treatment performed on the adherend on the fracture morphology was studied. Furthermore, the relationship between G1C and da/dN was systematically investigated. At a constant crack opening speed, the failure mode changed from cohesive to interfacial fracture, and then reverted back cohesive fracture as the deterioration of the specimens progressed due to increasing immersion time. Interfacial fracture was not observed for the specimens with sandblasted adherends. Lastly, a decrease in da/dN was not observed even with increasing G1C values of the immersed specimens because interfacial fracture was easy to occur when the cyclic strains were applied. [ABSTRACT FROM AUTHOR]

Double lap joints were prepared using epoxy adhesive and aluminum plates, and their high-temperature strength properties were studied. Tensile, thermal aging, creep, and cyclic fatigue tests were performed to systematically investigate the effects of the aging temperature, testing temperature, stress waveform, and stress ratio on the strength and fracture morphology of the double lap joints. When the specimen was exposed to 135°C, the strength decreased significantly. Also, the relationship between the test temperature and shear strength could be expressed using an equation obtained from thermal activation theory. Additionally, in the fatigue test at room temperature, the strength of the specimen subjected to constant stress was higher than that of the specimen subjected to cyclic strain. The effect of creep deformation increased in the creep test at high temperatures, and therefore, the strength decreased significantly. [ABSTRACT FROM AUTHOR]

Optical components are often adjusted to maintain their alignment along the optical axis. They are fixed at their optimal positions particularly using ultraviolet (UV) ray-curable adhesives. To achieve a micron-level positional accuracy, it is necessary to understand adhesive shrinkage while curing and the resulting deformation of the adhesive joint. However, it is challenging to perform a quantitative evaluation of the cure shrinkage and mechanical properties of adhesives given the process complexity and strong dependence on curing conditions. Therefore, this study clarified the effects of various curing conditions on the curing extent of an adhesive under UV curing for positioning and heat curing as a post-curing process. The cure shrinkage, coefficient of thermal expansion, and viscoelastic properties of the adhesive were also measured. Each material property could be defined as a function of the curing extent to predict the changes in the properties under different curing conditions. The adhesive curing process was divided into three stages: adhesive gelation under UV irradiation, fast reaction stage under heating, and slow reaction stage under heating. The adhesive state changed from viscous to viscoelastic to elastic as it cured, and this process proceeded in the aforementioned three stages. Three different formulae were fitted corresponding to each stage, with good agreement with the experimental measurements. [ABSTRACT FROM AUTHOR]

The effect of cyclic moisture-absorption/desorption on adhesive strength was investigated using water at 23°C. Bulk plates and open face lap joints were prepared using epoxy adhesive, and their weight transition and shear strength were measured. The diffusion coefficient of the absorption process increased with the number of cycles and reached a constant value. In contrast, the diffusion coefficient of the desorption process was not affected by the number of cycles. As a part of the calcium carbonate disappeared from the surface, the weight of the bulk plates was reduced, and this weight reduction was irreversible. However, the strength of the lap joint was not significantly damaged by moisture absorption at 23°C. [ABSTRACT FROM AUTHOR]

This article discusses the effectiveness of endoscopic hand suturing (EHS) in preventing postoperative bleeding in patients undergoing gastric endoscopic submucosal dissection (ESD). Postoperative bleeding is a common complication of ESD, especially in patients taking antithrombotic agents (ATAs). The study found that EHS, which involves suturing the mucosal defect using a flexible needle holder and absorbable barbed suture, was successful in preventing bleeding in high-risk patients. Further studies are needed to confirm the efficacy of this technique. [Extracted from the article]

The effect of strain rate on the mechanical properties of two epoxy adhesives was investigated by conducting experiments on dumbbell-shaped specimens prepared from the adhesives. The tensile rate was changed stepwise from 5.2 × 10–5 to 1.2 × 106 mm/min, and the yield stress, Young's modulus, elongation, and tensile strength were evaluated. The yield stress and tensile strength showed a clear dependence on the strain rate. The results from this study allowed us to propose a procedure for predicting the creep strength and high-rate impact strength from the results of a simple tensile test. [ABSTRACT FROM AUTHOR]

The application of primer is one of the most widely used pre-treatments to improve adhesion. However, few studies on the adhesive mechanism have investigated the effect of the organic solvent used for the primer on the improving of adhesion strength. In this study, attenuated total reflection infrared spectroscopy was performed to evaluate the interphases of multiple primers with different organic solvents for dilution. The main conclusion of this work is that the interphase thickness depends on the relative permittivity and viscosity of the organic solvent used for the primer. [ABSTRACT FROM AUTHOR]

Adhesive properties are often affected by water. In this study, to clarify the water-resistant properties of a thermosetting epoxy adhesive containing dicyandiamide (DICY) and carboxyl-terminated butadiene acrylonitrile rubber (CTBN), immersion tests of open-faced specimens and bulk specimens in water were performed, and the changes in the properties were investigated in terms of chemistry and mechanical strength. After immersing the open-faced specimens in water, the mechanical strengths were evaluated by two different methods: interfacial cutting method and secondary bonding method. Using both methods, a decrease in strength with immersion time was obtained, and the tendencies of the strength change were found to be very similar for the different evaluation methods. Chemical changes were also evaluated by infrared spectroscopy. Through periodical measurements of the infrared spectra of a fully-cured bulk adhesive specimen during water immersion, the chemical degradation of the epoxy adhesive containing DICY and CTBN was investigated, revealing an association with the change in mechanical strength in which hydrolysis of the cyano groups in DICY and CTBN led to a decrease in strength. Strength recovery experiments were also conducted by drying the specimens after water immersion, determining that the mechanical recovery strength changed with water temperature and immersion time. [ABSTRACT FROM AUTHOR]

This paper describes a phenomenological model for simulating the removal of toluene, ethylbenzene and o-xylene (TEX) from contaminated air streams by a biofilter. The phenomena incorporated into the model are interphase mass transfer between the gas and the aqueous biofilm with equilibrium partition, advection, diffusion, and biological reactions. The reaction rate for each TEX component is quantified using a more generalized Monod equation to allow for inhibitive effects in the presence of multiple substrates. Solutions to the system of coupled nonlinear partial differential equations representing component mass conservation are obtained by a fully implicit finite difference method with first-order accuracy in time and second-order accuracy in space. A parametric study is performed to evaluate the sensitivity of the Peclet number and the normalized mass transfer coefficient, both of which show strong influence on the removal rates. Comparison of the concentration distribution along the biofilter against available measured data and the exact closed-form solution indicates a good agreement with discrepancies being within experimental uncertainties.

Conventional test methods to evaluate the water resistance of adhesive joints are time-consuming. To reduce experimental time, open-faced specimens have been proposed. Numerical analysis indicated that the water absorption of an open-faced specimen was 3000 times faster than that of a conventional closed specimen. The strength of the interface between the adhesive and the adherend of the open-faced specimen was measured using the interfacial cutting method in this research. The resultant strength decreased with respect to immersion time in water, and this trend accelerated with an increase in the water temperature. When water was absorbed at temperatures below the glass transition temperature (Tg) of the adhesives, the strength was constant at 80–90% of the initial value in the first stage, and it decreased proportionally with logarithmic immersion time in the following stage. At water absorption above Tg, the interfacial strength initially proportionally decreased with the logarithmic immersion time. After the initial absorption, the slopes changed, and the strength slowly decreased. After further immersion for 59 days at 87°C, a sharp decrease in strength occurred. The reducing behaviour of the interfacial strength fitted the Arrhenius plot, which provided the estimated time to reach a specific strength by water immersion. [ABSTRACT FROM AUTHOR]

The improvement in adhesion technology for joining different types of materials has led to expectations of weight reduction in cars and commercial vehicles. Various levels of stress and stress ratios are loaded onto the joints of such transport vehicles. Therefore, the fatigue shear strength of an adhesive lap joint is important. This study is related to the fatigue properties of structural adhesive joints. Lap-joint specimens using epoxy adhesive were prepared, and fatigue tests with four different stress ratios were conducted. Subsequently, the fatigue limit diagram was plotted, and the effect of stress ratio on the fatigue limit was investigated. Moreover, the strength of the specimens subjected to various cyclic stress levels was investigated systemically. With cyclic shear stress, the influence of the shear stress amplitude on the resistance to fatigue failure was more significant than that of the number of cycles. The specimens that endured the fatigue tests maintained approximately the same shear strength as that of the as-received specimens. The findings of this study can provide important guidance for the design of a car body. [ABSTRACT FROM AUTHOR]