• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.270-275
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• 2016

High density polyethylene (HDPE)/kenaf fiber (KF) composites included two types of KF with different lengths were fabricated by using a twin screw extruder. A thermally expandable microcapsule (EMC) was used to form HDPE/KF. The KF lengths were 0.3 mm and 3 mm. The contents of KF and EMC were fixed at 20 wt% and 5 wt%, respectively. From FT-IR data of KF, which underwent chemical treatment, peaks around 1700 and $1300cm^{-1}$ decreased. This might be caused by the reduction of lignin and hemicellulose due to the chemical treatment of KF. Based on the specific gravity, thermal stability and tensile property, physical properties of the composites with a 3 mm fiber were good. However, if the fiber is longer, poor appearance might be caused due to the thermal degradation during processing. Thus, the adequate length of KF should be chosen to maintain the appearance and physical properties for industrial applications of HDPE/KF/EMC composites. The tensile strength for 0.3 mm fiber treated with chemicals increased slightly.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.11
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• pp.6649-6651
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• 2013

Background: Mdm2 binds to the amino-terminus of p53 to induce its degradation and a single nucleotide polymorphism in the MDM2 promoter region (T309G) has been reported to increase the risk of several carcinomas, such as gastric cancer. However, the results of published studies to analyze the association between MDM2 T309G and gastric cancer havve often conflicted. Methods: To better illustrate the filiation between MDM2 T309G and gastric cancer, we performed a meta-analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of the relationship. The pooled ORs were performed for 4 models, additive, recessive, co-dominant model, and dominant. Results: Nine published case-control studies including 3,225 gastric cancer cases and 4,118 controls were identified. The MDM2 T309G polymorphism was associated with a significantly increased risk of gastric cancer risk when all studies were pooled into the meta-analysis (GG versus TT, OR=1.57; 95%CI=1.57-2.12; p=0.003) and GG versus GT/TT, OR=1.52; 95%CI=1.217-1.90; p<0.001). Furthermore, Egger's test did not show any evidence of publication bias (P = 0.608 for GG versus TT). Conclusion: Our results suggest that the MDM2 T309G polymorphism is indeed associated with a significantly increased risk of gastric cancer.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.81-88
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• 2018

Spectrum sensing, the key technology of the cognitive radio networks, is used by a secondary user to determine the frequency state of a primary user. The energy detection in the spectrum sensing determines the presence or absence of a primary user according to the intensity of the allocated channel signal. Since this technique simply uses the strength of the signal for spectrum sensing, it is difficult to detect the signal of a primary user in the low SNR band. In this paper, we propose a way to combine spectrum sensing and support vector machine using wavelet packet decomposition to overcome performance degradation in low SNR band. In our proposed scheme, the sensing signals were extracted by wavelet packet decomposition and then used as training data and test data for support vector machine. The simulation results of the proposed scheme are compared with the energy detection using the AUC of the ROC curve and the accuracy according to the SNR band. With simulation results, we demonstrate that the proposed scheme show better determining performance than one of energy detection in the low SNR band.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.117-126
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• 2002

In this paper, 3-D fame design using second-orders plastic-hinge analysis accounting for lateral torsional buckling is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem associated with conventional second-order plastic-hinge analyses, which do not consider the degradation of the flexural strength caused by lateral torsional buckling, is overcome. Efficient ways of assessing steel frame behavior including gradual yielding associated with residual stresses and flexure, second-order effect, and geometric imperfections are presented. In this study, a model consisting of the unbraced length and cross-section shape is used to account for lateral torsional buckling. The proposed analysis is verified by the comparison of the LRFD results. A case studs shows that lateral torsional buckling is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient reliable tool ready to be implemented into design practice.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.516-522
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• 2002

For the experimental study of rotor steel, seven kind of specimens with different degradation levels were prepared by isothermal heat treatment at $630^{\circ}C$. Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel, and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steel's were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.13-21
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• 2002

In this paper, 3-D frame design using refined plastic-hinge analysis accounting for local buckling is developed. This analysis accounts for material and geometric nonlinearities of the structural system and its component members. Moreover, the problem associated with conventional refined plastic-hinge analyses, which do not consider the degradation of the flexural strength caused by local buckling, is overcome. Efficient ways of assessing steel frame behavior including gradual yielding associated with residual stresses and flexure, second-order effect, and geometric imperfections are presented. In this study, a model consisting of the width-thickness ratio is used to account for local buckling. The proposed analysis is verified by the comparison of the LRFD results. A case study shows that local buckling is a very crucial element to be considered in second-order plastic-hinge analysis. The proposed analysis is shown to be an efficient, reliable tool ready to be implemented into design practice.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.4
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• pp.323-333
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• 2005

Recently the fire is happening at the tunnel and underground - structure internationally. We are socially the economy the actual circumstances which serious loss is happening due to an fire occurrence when fire happened which is closed like tunnel and underground - structure, the collapse from the burglar degradation of strength of tunnel concrete lining and human life damage happen. It causes big problem while the long time disconnects a traffic network. While the fire happened in this research at the tunnel, the paper construct a basis data to deduce the specification regulation about stability of tunnel concrete lining. In this paper, the experiment was carried out for the prevention of explosive spalling of tunnel to use a reinforced Polypropylene concrete which mixes a Polypropylene which are known for the thing by being efficient at a protect of explosive spalling of the concrete. According to the firproof test result of reinforced Polypropylene admixture mortar, Polypropylene admixture of prevention of explosive spalling analyzed 0.2%-0.25%.

• Steel and Composite Structures
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• v.37 no.1
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• pp.15-26
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• 2020

The top-and-seat angles with double web angles are commonly used in the design of beam-to-column joints in Asian and North American countries. The seismic behavior analysis of these joints with large cross-section size of beam and column (often connected by four or more bolts) is a challenge due to the effects from the relatively larger size of stiffened angles and the composite action from the adjacent concrete slab. This paper presents an experimental investigation on the seismic performance of exterior composite beam-to-column joints with stiffened angles under cyclic loading. Four full-scale composite joints with different configuration (only one specimen contain top angle in concrete slab) were designed and tested. The joint specimens were designed by considering the effects of top angles, longitudinal reinforcement bars and arrangement of bolts. The behavior of the joints was carefully investigated, in terms of the failure modes, slippage, backbone curves, strength degradation, and energy dissipation abilities. It was found that the slippage between top-and-seat angles and beam flange, web angle and beam web led to a notable pinching effect, in addition, the ability of the energy dissipation was significantly reduced. The effect of anchored beams on the behavior of the joints was limited due to premature failure in concrete, the concrete slab that closes to the column flange and upper flange of beam plays an significant role when the joint subjected to the sagging moment. It is demonstrated that the ductility of the joints was significantly improved by the staggered bolts and welded longitudinal reinforcement bars.

• Korean Journal of Materials Research
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• v.17 no.7
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• pp.366-370
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• 2007

Silicon nitride ($Si_3N_4$) ceramics have been considered for various components of nuclear power plants such as the mechanical seal of a reactor coolant pump (RCP), the guide roller for a control rod drive mechanism (CRDM), and a seal support, etc. Corrosion behavior of $Si_3N_4$ ceramics in a high-temperature and high-pressure water must be elucidated before they can be considered as components for nuclear power plants. In this study, the corrosion behaviors of $Si_3N_4$ ceramics containing MgO and $Al_2O_3$ as sintering aids were investigated at a hydrothermal condition ($300^{\circ}C$, 9.0 MPa) in pure water and 35 ppm LiOH solution. The corrosion reactions were controlled by a diffusion of the reactive species and/or products through the corroded layer. The grain-boundary phase was preferentially corroded in pure water whereas the $Si_3N_4$ grain seemed to be corroded at a similar rate to the grain-boundary phase in LiOH solution. Flexural strengths of the $Si_3N_4$ ceramics were significantly degraded due to the corrosion reaction. Results of this study imply that a variation of the sintering aids and/or a control (e.g., crystallization) of the grain-boundary phase are necessary to increase the corrosion resistance of $Si_3N_4$ ceramics in a high-temperature water.

• Polymer(Korea)
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• v.38 no.2
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• pp.240-249
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• 2014

Multi-walled carbon nanotube (MWNT) reinforced poly(ethylene terephthalate) (PET) composites are studied. To increase the interfacial interactions between PET and MWNTs, the MWNTs are functionalized with bishydroxy-ethylene-terephthalate (BHET). The functionalized MWNTs are melt blended into PET matrix using a twin screw extruder. The amount of MWNTs loaded in PET matrix ranges from 0.5 to 2.0 wt%. After compounding and spinning, the filaments are post-drawn and annealed. To verify the chemical modifications of carbon nanotubes, Raman, $^1H$ NMR, XPS, TGA and FE-SEM are used. The nanocomposites are also analyzed with DSC, TGA, and UTM. These tests show that crystallization temperature and thermal degradation temperature increase due to the functionalized MWNTs. Also, tensile test shows that yield strength and toughness increase more than 30% with addition of only 1 wt% of MWNTs. These results show that the introduction of BHET onto the MWNTs is a very effective way in manufacturing MWNT/PET composite.