• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.252-261
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• 2023

Glucose detection is particularly important for clinical diagnosis and personal prevention and control. Herein, the smartphone-based amperometric glucose sensors were constructed using the NiS/CuS nanorods (NRs) as sensing electrodes. The NiS/CuS NRs were prepared through a facile hydrothermal process accompanied by the subsequent vulcanization treatment. The morphological and structural properties of NiS/CuS NRs were characterized with SEM, EDS, XRD, and XPS. Electrochemical measurements including cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy display that NiS/CuS NRs can act as highly efficient electrocatalyst for glucose detection. The NiS/CuS NRs electrodes present a wide detection range of 1-8000 µM for glucose sensing with the sensitivity of 956.38 µA·mM^-1·cm^-2. The detection limit was 0.35 µM (S/N=3). When employed in smartphone-based glucose sensing device, they also display a high sensitivity of 738.09 µA·mM^-1·cm^-2 and low detection limit of 1.67 µM. Moreover, the smartphone-based glucose sensing device also presents favorable feasibility in determination of glucose in serum samples with the recoveries ranging between 99.5 and 105.8%. The results may provide a promising viewpoint to design other new portable glucose sensors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.413-420
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• 2023

Among the seismic structures for reducing earthquake damage, the seismic control structure is a technology that can efficiently improve seismic performance and secure economic feasibility by simply applying a damper. However, existing dampers have limitations in terms of durability due to required seismic performance and material plasticity. In this study, we proposed a polyurethane damper with enhanced recovery characteristics by applying precompression to polyurethane, which basically shows elastic characteristics, and applying superelastic shape memory alloy (SSMA). To verify the characteristics of the polyurethane damper, the concept was first established, and the design details were completed by selecting SSMA and steel, and selecting the precompression size as design variables. In addition, structural tests were conducted to derive response behavior and analyze force resistance performance, residual displacement, recovery rate, and energy dissipation capacity. As a result of the analysis, the polyurethane damper showed that various performances improved when the SSMA wire was applied and the precompression increased.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.295-310
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• 2022

This paper proposes a modified bar simulation method for analyzing the shear lag effect of variable sectional box girder with multiple cells. This theoretical method formulates the equivalent area of stiffening bars and the allocation proportion of shear flows in webs, and re-derives the governing differential equations of bar simulation method. The feasibility of the proposed method is verified by the model test and finite element (FE) analysis of a simply supported multi-cell box girder with constant depth. Subsequently, parametric analysis is conducted to explore the mechanism of shear lag effect of varied sectional cantilever box girder with multiple cells. Results show that the shear lag behavior of variable box-section cantilever box girder is weaker than that of box girder with constant section. It is recommended to make the gradient of shear flow in the web with respect to span length vary as smoothly as possible for eliminating the shear lag effect of box girder. An effective countermeasure for diminishing shear lag effect is to increase the number of box chambers or change the variation manner of bridge depth. The shear lag effect of varied sectional cantilever box girder will get more server when the length of central flanges is shorter than 0.26 or longer than 0.36 times of total width of top flange, as well as the cantilever length exceeds 0.29 times of total length of box's flange. Therefore, the distance between central webs can adjust the shear lag effect of box girder. Especially, the width ratio of cantilever plate with respect to total length of top flange is proposed to be no more 1/3.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.390-390
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• 2013

Use of recycled aggregates in portland cement concrete construction can offer benefits associated with both economy and sustainability. Testing performed to date indicates that RBMA can be used as a 100% replacement for conventional coarse aggregate in concrete that exhibits acceptable mechanical properties for use in structural and pavement elements, including satisfactory performance in some durability tests. RBMAC is currently not used in any type of construction in the United States. However, use of RBMAC could become a viable construction strategy as sustainable building practices become the norm. Rating systems such as LEED offer points for reuse of building materials (particularly on-site) and use of recycled materials. If renovations at an existing facility call for the demolition of existing brick masonry constructions, the rubble could be included as RBMA in new concrete pavement, sidewalks, or curb and gutter. Other potential uses for RBMAC could include those in the precast concrete industry, particularly in architectural precast concrete applications. In addition to providing acceptable strength and economy, the color of RBMA could be an attractive component of architectural precast concrete panels or other façade components. This paper explores the feasibility of use of RBMAC in several types of sustainable construction initiatives, based upon the findings of previous work with RBMAC produced from construction and demolition waste from a case study site. Guidance for obtaining and using RBMA is presented, along with a summary of material properties of RBMAC that will be useful to construction professionals.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.71-84
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• 2023

In accordance with Korean structural foundation design standards, dynamic or static load tests are mandated for 1 to 3% of total piles. The construction quality of the remaining 97% to 99% of piles is determined through penetration measurements. This study aims to enhance the quality control of the majority of piles by adopting a pile driving formula that considers both penetration and hammer energy. The current challenge lies in adapting existing overseas driving formulas to the domestic site conditions, characterized by shallow weathered or soft rocks, and the prevalent use of pre-bored piles. To address this, the Modified Gates formula was refined using domestic dynamic load data, thereby improving its applicability to pile management. Despite employing fewer variables, the proposed formula demonstrates a comparable accuracy to dynamic loading tests in predicting the bearing capacity of pre-bored piles. Consequently, this formula holds promise for practical use in future pile quality management.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.27-40
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• 2024

The prediction of VIV amplitude is essential for the design and fatigue life estimation of steel tubes in tubular transmission towers. Limited to costly and time-consuming traditional experimental and computational fluid dynamics (CFD) methods, a machine learning (ML)-based method is proposed to efficiently predict the VIV amplitude of steel tubes in transmission towers. Firstly, by introducing the first-order mode shape to the two-dimensional CFD method, a simplified response analysis method (SRAM) is presented to calculate the VIV amplitude of steel tubes in transmission towers, which enables to build a dataset for training ML models. Then, by taking mass ratio M^*, damping ratio ξ, and reduced velocity U^* as the input variables, a Kriging-based prediction method (KPM) is further proposed to estimate the VIV amplitude of steel tubes in transmission towers by combining the SRAM with the Kriging-based ML model. Finally, the feasibility and effectiveness of the proposed methods are demonstrated by using three full-scale steel tubes with C-shaped, Cross-shaped, and Flange-plate joints, respectively. The results show that the SRAM can reasonably calculate the VIV amplitude, in which the relative errors of VIV maximum amplitude in three examples are less than 6%. Meanwhile, the KPM can well predict the VIV amplitude of steel tubes in transmission towers within the studied range of M^*, ξ and U^*. Particularly, the KPM presents an excellent capability in estimating the VIV maximum amplitude by using the reduced damping parameter S_G.

• Structural Monitoring and Maintenance
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• v.10 no.4
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• pp.315-337
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• 2023

During the design phase, it is crucial to determine the interface stresses between the reinforcing plate and the concrete base in order to predict plate end separation failures. In this work, a simple theoretical study of interface shear stresses in beams reinforced with P-FGM and E-FGM plates subjected to an arbitrarily positioned point load, or two symmetrical point loads, was presented using the linear elastic theory. The presence of pores in the reinforcing plate distributed in several forms was also taken into account. For this purpose, we analyze the effects of porosity and its distribution shape on the interracial normal and shear stresses of an FGM beam reinforced with an FRP plate under different types of load. Comparisons of the proposed model with existing analytical solutions in the literature confirm the feasibility and accuracy of this new approach. The influence of different parameters on the interfacial behavior of reinforced concrete beams reinforced with functionally graded porous plates is further examined in this parametric study using the proposed model. From the results obtained in this study, we can say that interface stress is significantly affected by several factors, including the pores present in the reinforcing plate and their distribution shape. Additionally, we can conclude from this study that reinforcement systems with composite plates are very effective in improving the flexural response of reinforced RC beams.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.20 no.1
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• pp.49-55
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• 2024

Stainless 630 (or 17-4PH) is a precipitation-hardening martensitic stainless steel that has excellent mechanical properties and corrosion resistance. These characteristics make the STS630 to be used as a consisting material for various components such as spider, pin, spring, and spring retainer, of the control rod drive mechanism (CRDM) in pressurized water reactors (PWRs). In general, it is well known that the oxide layer of stainless steel consists of a duplex layer, a compact inner layer of FeCr₂O₄ spinel, and a coarse-grained outer layer of Fe₃O₄ spinel in PWR primary coolant condition. However, the characteristics of the oxide layer can be sensitively influenced by various water chemistry conditions such as temperature, dissolved oxygen, dissolved hydrogen, pH, pH adjuster type, and exposure time. In this work, we investigate the corrosion properties of the STS630 as a function of coolant temperature in an NH3 alkaline solution for its boron-free application in a small modular reactor, to confirm the feasibility for usage as a boron-free SMR structural material. As a result, oxide layer of corroded STS630 is consist of double-layer oxides consisting of a Cr-rich dense inner oxide and a Fe-rich polyhedral outer particles like as that in commercial PWR primary coolant. The corrosion rate of STS630 increases with increase in test time and temperature and the corrosion rate-time model equation was developed based on experimental data. Overall, it is expected that the results in this study provides useful data for the corrosion behavior of STS630 in alkaline environments, contributing to the development of selecting suitable materials for SMRs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.33-39
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• 2015

Recently, the event of slope failure has been occurring frequently due to rapid climate changes and broad development of infrastructures, and the research for establishment of monitoring and prevention system has been an attentive issue. The major influence factors of slope failure mechanism can be considered moisture and temperature in soil, and the slope failure can be monitored and predicted through the trend of moisture-temperature change. Therefore, the combined sensing technology for the continuous measurement of moisture-temperature with different soil depths is needed for the slope monitoring system. The various independent sensors for each item (i.e. temperature and moisture respectively) have been developed, however, the research for development of combined sensing system has been hardly carried out. In this study, the high-fidelity sensor combing temperature-moisture measurement by using the minimized current consuming temperature circuit and the microwave emission moisture sensor is developed and applied on the slope failure monitoring system. The feasibility of developed monitoring system is verified by various experimental approaches such as standard performance test, mockup test and long-term field test. As a result, the developed temperature-moisture combined measurement system is verified to be measuring and monitoring the temperature and moisture in soil accurately.

• Journal of Korean Academy of Nursing
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• v.27 no.3
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• pp.614-626
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• 1997

The main purposes of the study were to develop and test a model which explains the dynamic relationship among factors reported as affecting to the quality of life of individuals with rheumatoid arthritis and to examine the relationship between self-help response and quaility of life. Data for the study were collected from March 1996 to December 1996 from 153 female patients who regularly visited a clinic for people with rheumatism. The patients were introduced to the investigators by nurses who worked at that clinic, and then the investigator interviewed the patients for 30 to 40 minutes to collect the data. Instruments used in the study were modified self-report questionaires from the ones which were already developed in previous studies or from related literature. Data analysis were performed using LISREL(Lineal Structural Relations) 8 program to test whether the proposed hypothesized model fit the collected data. To test the fitablity of the hypothesized model both a general fit measure and a detailed fit measure were used. Based on the test results from the various fit measures, the hypothesized model was found to be well suited to the real data. As characteristics related to illness becomes severe, the feasibility for these characteristics leading to the perception of uncertainty about the illness tend to increase, but, the direct effects from the illness characteristics(such as level of physical symptoms, sense of social-psychologic change, limitations of action) as they are related to the other intrinsic variables (self-efficacy or self-help behavior and quality of life), were found to be not significant. It was found that uncertainty had a direct effect on self-efficacy but did not have a direct effect on self-help behavior or quality of life. Also, it is noted that self-efficacy had a positive effect on self-help behavior and quality of life and there was a bilateral relationship between self-efficacy and self-help behavior. Lastly, the hypothesis proposed from the theoretical model in this study was supported basis of the results that self-help behavior provides both direct and positive effects to quality of life. Particularity, since a bilateral relationship was also found between self-help behavior and quality of life in the modified model, as self-help behavior increased, so did quality of life. And, reversely, as quality of life increased, so did self-help behavior. In conclusion, the results of this study suggest that focusing on both acquirement and reinforcement of adjustment factors or self-help behavior is more efficient than focusing on the characteristics of illness in establishing the stategies for improving quality of life of individuals with rheumatoid arthritis.