• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.140-146
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• 2023

Water quality is crucial for human health and the environment. Accurate measurement of the quantity of organic carbon in water is essential for water quality evaluation, identification of water pollution sources, and appropriate implementation of water treatment measures. Total organic carbon (TOC) analysis is an important tool for this purpose. Although other methods, such as chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are also used to measure organic carbon in water, they have limitations that make TOC analysis a more favorable option in certain situations. For example, COD requires the use of toxic chemicals, and BOD is time-consuming and can produce inconsistent and unreliable results. In contrast, TOC analysis is rapid and reliable, providing accurate measurements of organic carbon content in water. However, common methods for TOC analysis can be complex and energy-intensive because of the use of high-temperature heaters for liquid-to-gas phase transitions and the use of acid, which present safety risks. This study focuses on a TOC analysis method using TiO₂ photocatalysis, which has several advantages over conventional TOC analysis methods, including its low cost and easy maintenance. For TiO₂, rutile and anatase powders are mixed with an inorganic binder and spray-coated onto a glass fiber substrate. The TiO₂ powder and inorganic binder solutions are adjusted to optimize the photocatalytic reaction performance. The TiO₂ photocatalysis method is a simple and low-power approach to TOC analysis, making it a promising alternative to commonly used TOC analysis methods. This study aims to contribute to the development of more efficient and cost-effective approaches for water quality analysis and management by exploring the effectiveness and reliability of the developed equipment.

• Fibers and Polymers
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• v.7 no.4
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• pp.404-413
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• 2006

This study examines multiple quality optimization of the injection molding for Polyether Ether Ketone (PEEK). It also looks into the dimensional deviation and strength of screws that are reduced and improved for the molding quality, respectively. This study applies the Taguchi method to cut down on the number of experiments and combines grey relational analysis to determine the optimal processing parameters for multiple quality characteristics. The quality characteristics of this experiment are the screws' outer diameter, tensile strength and twisting strength. First, one should determine the processing parameters that may affect the injection molding with the $L_{18}(2^1{\times}3^7)$ orthogonal, including mold temperature, pre-plasticity amount, injection pressure, injection speed, screw speed, packing pressure, packing time and cooling time. Then, the grey relational analysis, whose response table and response graph indicate the optimum processing parameters for multiple quality characteristics, is applied to resolve this drawback. The Taguchi method only takes a single quality characteristic into consideration. Finally, a processing parameter prediction system is established by using the back-propagation neural network. The percentage errors all fall within 2%, between the predicted values and the target values. This reveals that the prediction system established in this study produces excellent results.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.535-546
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• 2018

The objective of this study is to understand the behaviour of hollow core slabs strengthened with FRP and hybrid techniques through numerical and analytical studies. Different strengthening techniques considered in this study are (i) External Bonding (EB) of Carbon Fiber Reinforced Polymer (CFRP) laminates, (ii) Near Surface Mounting (NSM) of CFRP laminates, (iii) Bonded Overlay (BO) using concrete layer, and (iv) hybrid strengthening which is a combination of bonded overlay and NSM or EB. In the numerical studies, three-dimensional Finite Element (FE) models of hollow core slabs were developed considering material and geometrical nonlinearities, and a phased nonlinear analysis was carried out. The analytical calculations were carried out using Response-2000 program which is based on Modified Compression Field Theory (MCFT). Both the numerical and analytical models predicted the behaviour in agreement with experimental results. Parametric studies indicated that increase in the bonded overlay thickness increases the peak load capacity without reducing the displacement ductility. The increase in FRP strengthening ratio increased the capacity but reduced the displacement ductility. The hybrid strengthening technique was found to increase the capacity of the hollow core slabs by more than 100% without compromise in ductility when compared to their individual strengthening schemes.

• Steel and Composite Structures
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• v.23 no.5
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• pp.529-541
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• 2017

In the present study, vibration analysis of functionally graded carbon nanotube reinforced composite (FGCNTRC) plate moving in two directions is investigated. Various types of shear deformation theories are utilized to obtain more accurate and simplest theory. Single-walled carbon nanotubes (SWCNTs) are selected as a reinforcement of composite face sheets inside Poly methyl methacrylate (PMMA) matrix. Moreover, different kinds of distributions of CNTs are considered. Based on extended rule of mixture, the structural properties of composite face sheets are considered. Motion equations are obtained by Hamilton's principle and solved analytically. Influences of various parameters such as moving speed in x and y directions, volume fraction and distribution of CNTs, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of composite plate on the vibration characteristics of moving system are discussed in details. The results indicated that thenatural frequency or stability of FGCNTRC plate is strongly dependent on axially moving speed. Moreover, a better configuration of the nanotube embedded in plate can be used to increase the critical speed, as a result, the stability is improved. The results of this investigation can be used in design and manufacturing of marine vessels and aircrafts.

• Structural Engineering and Mechanics
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• v.63 no.3
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• pp.269-280
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• 2017

One major concern that has occupied the mind of the designers is a structural failure as result of stress concentration in the geometrical discontinuities. Understanding the effective parameters contribute to stress concentration and proper selection of these parameters enables the designer get to a reliable design. In the analysis of perforated isotropic and orthotropic plates, the effective parameters on stress distribution around holes include load angle, curvature radius of the corner of the hole, hole orientation and fiber angle for orthotropic materials. This present paper tries to examine the possible effects of these parameters on stress analysis of infinite perforated plates with central quasi-square hole applying grey wolf optimizer (GWO) inspired by the particular leadership hierarchy and hunting behavior of grey wolves in nature, and also the present study tries to introduce general optimum parameters in order to achieve the minimum amount of stress concentration around this type of hole on isotropic and orthotropic plates. The advantages of grey wolf optimizer are stout, flexible, simple, and easy to be enforced. The used analytical solution is the expansion of Lekhnitskii's solution method. Lekhnitskii applied this method for the stress analysis of anisotropic plates containing circular and elliptical holes. Finite element numerical solution is employed to examine the results of present analytical solution. Results represent that by selecting the aforementioned parameters properly, fewer amounts of stress could be achieved around the hole leading to an increase in load-bearing capacity of the structure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.4
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• pp.497-509
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• 1996

Evacuated powder insulations have long been known to have better thermal performance than existing commercially available insulators, such as fiber glass and CFC-blown foam. To make a composite powder panel, a series of individually evacuated panels was encapsulated in a rigid closed cell foam matrix. The panels were encapsulated in a thin glass sheet barrier to preserve the vacuum. The thermal conductivity of the individual panel was found to be $0.0062W/m^{\circ}K$ by experiment and the polyurethane foam above had a thermal conductivity of $0.024W/m^{\circ}K$. In this study, numerical analysis using finite element method was carried out to investigate insulation performance of rigid foam/evacuated powder composite panel with respect to panel geometries such as panel pitch, panel aspect ratio and panel area ratio. Numerical analysis has indicated that more optimal vacuum panel geometries, much lower overall thermal conductivities can be achieved.

• Composites Research
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• v.30 no.2
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• pp.149-157
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• 2017

In this paper, fracture behavior of laminated composites with notch was studied by cohesive zone modeling approach. The numerical modeling proceeded by first generating 3 dimensional solid element meshes for notched laminated composite coupon configurations. Then cohesive elements representing failure modes of fiber fracture, matrix cracking and delamination were inserted between bulk elements in all regions where the corresponding failures were likely to occur. Next, progressive failure analyses were performed simulating uniaxial tensile tests. The numerical results were compared to those by experiment available in the literature for verification of the analysis approach. Finally, notched laminated composite configurations with selected stacking sequences were analyzed and the failure behavior was carefully examined focusing on the failure initiation and progression and the dominating failure modes.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.4
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• pp.495-503
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• 1999

Airborne particulate matter $(PM_{10})$ collected using high volume air sampler and silica fiber filter were analyzed by Instrumental Neutron Activation Analysis(INAA), Inductively Coupled Plasma Atomic Emission Spectrometry(ICP-AES) and Atomic Absorption Spectrometry(AAS), and the results were compared with each other. 30~40 trace elements in environmental standard reference materials(NIST SRM 1648 and NIES CRM No.8) were analyzed for the analytical quality control. The relative error for two-third of elements detected was less than 10%, and the standard deviation was less than 15%. During the sampling period for 24 hours, the mass concentration of total suspended particulate was 36.1$\mu\textrm{g}$/㎥ and the value is lower than the critical level in Korea. In the results of NAA, the elements of Al, As, Ba, Fe, La, Mg, Na, Sb, Zn were well agreed with those of other methods. In statistical estimation between different methods, the deviation of Al, Ba, Cr, Fe was less than 10% and quite reliable.

• Computers and Concrete
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• v.8 no.6
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• pp.717-733
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• 2011

Strengthening of reinforced concrete (RC) members against shear that is one of the failure modes especially avoided by using carbon fiber reinforced polymer (CFRP) is widely used technique, which is studied at many experimental studies. However, conducting experimental studies are required more financial resources and laboratory facilities. In addition, along with financial resources, more time is needed in order to carry out comprehensive experimental studies. For these reasons, a verified finite element model that is tested with previous experimental studies can be used for reaching generalized results and investigating parameters that are not studied. For this purpose, previous experimental study results are used and "T" cross-sectioned RC beams strengthened with CFRP strips with insufficient shear strength are modeled by using ANSYS software. First, finite elements modeling of the previously tested RC beams are done, and then the computed results are compared with the experimental ones whether they are matched or not. As a result, the finite element model is verified. Later, analyses of the cases without any test results are done by using the verified model. Optimum CFRP strip spacing is determined with this verified finite element model, and compared with the experimental findings.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.45-49
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• 2006

The thermal degradation of carbon fiber reinforced phenolic composites have been studied at high temperature by using thermogravimetry analysis (TGA). The aim is that ultimately it can be used to predict the service temperature during solid rocket firing for any level and type of mechanical loading and to recommend protection systems required. To simulate the high heating rate in firing condition, the modified thermal decomposition constant (1000 K/min) was used for FEM analysis. The temperature distribution and the thickness of thermal decomposition were estimated well and we could predict the thickness of thermal decomposition within ${\pm}1mm$.