• Design & Manufacturing
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• v.18 no.2
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• pp.57-63
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• 2024

In this study, the recyclability of commonly used PP (polypropylene) and ABS (acrylonitrile butadiene styrene) was evaluated by molding test specimens from mixture of virgin and shredded material, followed by measuring their strength properties, Experiments were conducted o two type of PP (transparent and non-transparent) and two types of ABS (white and yellow). Test specimens for each resin were prepared with shredded material ratios ranging from 10% to 50% in 10% increments. Changes in tensile strength, elastic modulus, and elastic limit were analyzed based on the mixing ratio of the shredded material. The experimental results demonstrated that the strength properties of all the resins remained consistent within a certain range, even with increasing proportions of shredded material. For transparent PP, the tensile strength ranged from 30.87± MPa, the elastic modulus from 1.23±0.04 GPa, and the elastic limit from 19.17±0.44%. Non-transparent PP exhibited a tensile strength ranging from 27.71±0.58 MPa, an elastic modulus from 1.03±0.06 GPa, and an elastic limit from 17.35±0.41%. For ABS, white ABS had a tensile strength of 39.42±0.28 MPa, an elastic modulus of 1.94±0.01 GPa, and an elastic limit of 36.76±0.25%. Yellow ABS showed a tensile strength of 39.25±0.78 MPa, an elastic modulus of 1.94±0.01 GPa, and an elastic limit of 37.14±0.23%, with values remaining consistent within this range. Based on these results, it was confirmed that the mechanical properties of the resins used in this study do not change significantly when mixed with recycled shredded material, indicating excellent mechanical recyclability.

• International Journal of Advanced Culture Technology
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• v.2 no.2
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• pp.15-18
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• 2014

This paper presents a sensor location decision making method respect to Container-Grown Seedlings in view of precision agriculture (PA) when sensors involved in tree container measure received signal strength (RSS) or time-of-arrival (TOA) between themselves and neighboring sensors. A small fraction of sensors in the container-grown seedlings system have a known location, whereas the remaining locations must be estimated. We derive Rao-Cramer bounds and maximum-likelihood estimators under Gaussian and log-normal models for the TOA and RSS measurements, respectively.

• Journal of Mechanical Science and Technology
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• v.18 no.8
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• pp.1368-1374
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• 2004

The remaining life estimation for the aged components in power plants as well as chemical plants are very important because mechanical properties of the components are degraded with in-service exposure time in high temperatures. Since it is difficult to take specimens from the operating components to evaluate mechanical properties of components, nondestructive techniques are needed to evaluate the degradation. In this study, test materials with several different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C$. The DC potential drop method and destructive methods such as tensile and fracture toughness were used in order to evaluate the degradation of 1Cr-1Mo-0.25V steels. In this result, we can see that tensile strength and fracture toughness can be calculated from resistivity and it is possible to evaluate material degradation using DC potential drop method, non-destructive method.

• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.167-178
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• 2009

Initial imperfections, such as initial deflection or remaining stress, cause deterioration of buckling strength of structures. The Koiter imperfection sensitivity law has been extended to describe the mechanism of reduction for structures. The extension is twofold: (1) a number of imperfections are considered, and (2) the second order (minor) imperfections are implemented, in addition to the first order (major) imperfections considered in the Koiter law. Yet, in reality, the variation of external loads is dominant over that of imperfection. In this research, probabilistic evaluation of buckling loads against external loads subjected to probabilistic variation is conducted by extending the concept of imperfection sensitivity. A truss arch subjected to dead and live loads is considered as a numerical example. The mechanism of probabilistic variation of buckling strength of this arch is described by the proposed method, and its reliability is evaluated.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.3
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• pp.148-155
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• 2003

In this paper, a nonlinear anisotropic filtering method without the loss of important information happened due to the repeated filtering in magnetic resonance images is proposed. First of all original images are divided into four regions, e.g., SPR(Strong Plain Region), EPR(Easy Plain Region), SER(Strong Edge Region), and EER(Easy Edge Region). An optimal template among multiple templates is selected, then the nonlinear anisotropic filtering based on the template is applied in pixel by pixel basis. In the proposed algorithm, filtering strength of EER containing important information is adjusted very weak and filtering strength for remaining regions is also adjusted according to the degree of the importance. In spite of repeated filtering, resulting images by the proposed method could still preserve anatomy information of original images without any degradation. Compared to the existing nonlinear anisotropic filtering, the proposed filtering method with multiple templates provides higher reliability for filtered images.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.61-62
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• 2019

With development of IT technology, the ubiquitous has been realized in various industry. In construction industry, as well, end-edge techniques have been introduced such as managing technique the temperature and compressive strength of the concrete placed in structure in domestic and abroad project sites. However, several problems were found during application at the actual field regarding difficulties of connecting Bluetooth communication due to the short communication range, diffuse reflection caused by aluminum formwork, and high cost by using one-time sensor. Therefore to recover these shortages, and improve the performances, the wireless sensor network based concrete IoT management system for concrete early-age quality management was developed.

• Journal of the Korean Institute of Gas
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• v.23 no.5
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• pp.1-7
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• 2019

Although the rupture pressure is evaluated from remaining strength when a flaw is defected to cylinder surface, but the rupture pressure can be not easy to estimate for the composite cylinders. In this study, the area capacity method is developed for the type-3 cylinders that is based on the result applied area capacity method of type-1 cylinders. And the reliability is validated by bursting test with artificial flaw at the cylinder surface. The predicted data of area capacity method and experimental results have very similar tendency. This method and results will be a very important records in field of rupture pressure estimations.

• Restorative Dentistry and Endodontics
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• v.39 no.2
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• pp.95-103
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• 2014

Objectives: This study evaluated the effect of three antioxidizing agents on pullout bond strengths of dentin treated with sodium hypochlorite. Materials and Methods: Root canals of 75 single-rooted human teeth were prepared. Fifteen teeth were irrigated with normal saline for a negative control group, and the remaining 60 teeth (groups 2 - 5) with 2.5% NaOCl. The teeth in group 2 served as a positive control. Prior to post cementation, the root canals in groups 3 - 5 were irrigated with three antioxidizing agents including 10% rosmarinic acid (RA, Baridge essence), 10% hesperidin (HPN, Sigma), and 10% sodium ascorbate hydrogel (SA, AppliChem). Seventy-five spreaders (#55, taper .02, Produits Dentaires S.A) were coated with silica and silanized with the Rocatec system and ceramic bond. All the prepared spreaders were cemented with a self-adhesive resin cement (Bifix SE, Voco Gmbh) in the prepared canals. After storage in distilled water (24 h/$37^{\circ}C$), the spreaders were pulled out in a universal testing machine at a crosshead speed of 1.0 mm/min. Pull-out strength values were analyzed by one-way ANOVA and Tukey's HSD test (${\alpha}$ = 0.05). Results: There were significant differences between study groups (p = 0.016). The highest pullout strength was related to the SA group. The lowest strength was obtained in the positive control group. Conclusions: Irrigation with NaOCl during canal preparation decreased bond strength of resin cement to root dentin. Amongst the antioxidants tested, SA had superior results in reversing the diminishing effect of NaOCl irrigation on the bond strength to root dentin.

• Geomechanics and Engineering
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• v.23 no.3
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• pp.227-244
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• 2020

Earthen structures have an excellent bioclimatic performance, but they are vulnerable against earthquakes. In order to investigate the edification process and costs, a full-scale rammed soil house was constructed in 2004. In 2016-2019, it was studied its seismic damage, durability and degradation process. During 2004-2016, the house presented a relatively good seismic performance (M_w=5.6-6.4). The damaged cover contributed in the fast deterioration of walls. In 2018 it was observed a partial collapse of one wall due to recent seismicity (M_w=5.6-6.1). The 15-year-old samples presented a reduced compressive strength (0.040 MPa) and a minimum moisture (1.38%). It is estimated that the existing house has approximately a remaining 20% of compressive strength with a degradation of about 5.4% (0.0109 MPa) per year (considering a time frame of 15 years) if compared to the new soil samples (0.2028 MPa, 3.52% of moisture). This correlation between moisture and compressive strength degradation was compared with the study of new soil samples at the same construction site and compared against the extracted samples from the 15-year-old house. At 7-14-days, the specimens presented a similar compressive strength as the degraded ones, but different moisture. Conversely, the 60-days specimens shown almost five times more strength as the existing samples for a similar moisture. It was observed in new rammed soil that the lower the water content, the higher the compressive/shear strength.

• Restorative Dentistry and Endodontics
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• v.45 no.2
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• pp.19.1-19.8
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• 2020

Objective: This study aimed to evaluate the effect of ultrasonic cleaning of the intracanal post space on the bond strength of fiber posts in oval canals filled with a premixed bioceramic (Bio-C Sealer [BIOC]) root canal sealer. Materials and Methods: Fifty premolars were endodontically prepared and divided into 5 groups (n = 10), based on the type of root canal filling material used and the post space cleaning protocol. A1: gutta-percha + AH Plus (AHP) and post space preparation with ultrasonic cleaning, A2: gutta-percha + BIOC and post space preparation with ultrasonic cleaning, B1: gutta-percha + AHP and post space preparation, B2: gutta-percha + BIOC and post space preparation, C: control group. Fiber posts were cemented with a self-adhesive luting material, and 1 mm thick slices were sectioned from the middle and cervical third to evaluate the remaining filling material microscopically. The samples were subjected to a push-out test to analyze the bond strength of the fiber post, and the results were analyzed with the Shapiro-Wilk, Bonferroni, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). Failure modes were evaluated using optical microscopy. Results: The results showed that the fiber posts cemented in canals sealed with BIOC had lower bond strength than those sealed with AHP. The ultrasonic cleaning of the post space improved the bond strength of fiber posts in canals sealed with AHP, but not with BIOC. Conclusions: BIOC decreased the bond strength of fiber posts in oval canals, regardless of ultrasonic cleaning.