• Steel and Composite Structures
• /
• v.20 no.6
• /
• pp.1205-1219
• /
• 2016

This paper presents a new type of pre-pressed spring self-centering energy dissipation (PS-SCED) bracing system that combines friction mechanisms between the inner and outer tube members to provide the energy dissipation with the pre-pressed combination disc springs installed on both ends of the brace to provide the self-centering capability. The mechanics and the equations governing the design and hysteretic responses of the bracing system are outlined, and a series of validation tests of components comprising the self-centering mechanism of combination disc springs, the friction energy dissipation mechanism, and a large scale PS-SCED bracing specimen were conducted due to the low cyclic reversed loadings. Experimental results demonstrate that the proposed bracing system performs as predicted by the equations governing its mechanical behaviors, which exhibits a stable and repeatable flag-shaped hysteretic response with excellent self-centering capability and appreciable energy dissipation, and large ultimate bearing and deformation capacities. Results also show that almost no residual deformation occurs when the friction force is less than the initial pre-pressed force of disc springs.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.3
• /
• pp.475-488
• /
• 2017

Wear prediction of TBM disc cutters is a very important issue for hard rock TBMs as number of cutter head intervention. In this regard, some model such as NTNU, Gehring model, CSM models have been used to predict disc cutter wear and intervention interval. There are some deficiencies in these models. This paper developed a new test method for wear prediction for TBM disc cutter and proposed a new abrasion index. In this regard, different abrasivity indices along with their testing methods are explained. A comparative study is performed to develop the predictability of different cutter life evaluation methods and index. The evaluation of the new methods proposed in this paper shows a very good agreement with the actual cutter life and intervention interval length. The proposed tester and index can be easily used to predict the intervention interval length and cutter wear evaluation in both planning and construction stages of a TBM tunneling project.

• Natural Product Sciences
• /
• v.4 no.3
• /
• pp.130-135
• /
• 1998

The water extracts of 83 oriental herbal medicines (Hanbang) which have been clinically used to treat bacterial infections in Korea were screened for in vitro antibacterial activity by the paper disc assay method. Two Gram positive bacteria, Staphylococcus aureus SG 511, Bacillus subtilis ATCC 6633, and two Gram negative bacteria, Escherichia coli 055, Pseudomonas aeruginosa 9027 were used as test organisms. Among the extracts tested, MeOH extract of Baenongtang showed remarkably potent antibacterial activity. Activity-guided chromatographic fractionations of the $CH_2Cl_2$ extract of Baenongtang afforded seven antibacterial compounds.

• Journal of Life Science
• /
• v.10 no.5
• /
• pp.524-528
• /
• 2000

Antimicrobial and antioxidative effects of Alismatis Rhizoma which has been used as a galenic for diuretic and antiphlogistic were investigated. In a paper disc test, water extract of Alismatis Rhizoma showed antimicrobial activities against almost all of the microbial species tested, while their activities of methanol and ethanol extract was low than the activity of water extract, and the antimicrobial activity of water extract was most prominent against Vibrio parahaemolyticus. Antioxidative activity against linoleic acid was not observed in methanol extract. In contrast to methanol and ethnol and ethanol extract, water extract showed a antioxidative activity against linoleic acid. However, the antioxidative of water extract was lower than that of 0.1% BHT.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.546-552
• /
• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• Transactions of Materials Processing
• /
• v.31 no.1
• /
• pp.11-16
• /
• 2022

In this paper, wear characteristics of PVD coatings were compared on the die surface for cold stamping of MART1470 steel sheet with the finite element analysis and the pin-on-disc wear test. Three types of PVD coatings (CrN, TiAlCrN, and MoS2TiCr(W)N) were considered for the tool surface made of STD11 material. The stamping process of an auto-body part was analyzed with the finite element method. Ranges of process variables for the wear test such as contact pressure, relative speed, and sliding distance were predicted from analysis results. In order to quantitatively analyze wear characteristics of each coating, the amount of wear was measured and compared according to process variables with the pin-on-disc wear test. The influence of each process variable was investigated and the wear characteristics of the three coating layers were quantitatively compared. It was confirmed that the wear characteristics of MoS₂TiCr(W)N coating were better than those of CrN and TiAlCrN. It was noted that the proposed prediction approach could predict and respond to the wear phenomenon occurring in the stamping process.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.3
• /
• pp.53-60
• /
• 2008

Recently, various recording technologies are studied for optical data storage. After standardization of BD (Blue-ray Disc) and HD-DVD (High-Definition Digital Versatile Disc), the industry is looking for a suitable technology for next generation optical data storage. Super-RENS (Super-resolution near field structure) technique, which is capable of compatibility with other systems, is one of next optical data storage. In this paper, we analyze the nonlinearity of Super-RENS read-out signal through the bicoherence test, which uses HOS (Higher-Order Statistics) and apply neural networks for nonlinear modeling. The model structure considered in this paper is the NARX (Nonlinear AutoRegressive eXogenous) model. The experiment results indicate that the read-out signals have nonlinear characteristics. In addition, it verified the possibility that neural networks can be utilized for nonlinear modeling of Super-RENS systems.

• Journal of Korea Multimedia Society
• /
• v.12 no.3
• /
• pp.329-334
• /
• 2009

When an optical disc is being played. the pick-up converts light to analog signal at first. The analog signal is equalized for removing the inter-symbol interference and then the equalized analog signal is converted into the digital signal for extracting the synchronized data and clock signals. There are a lot of algorithms that minimize the BER in extracting the synchronized data and clock when high. density optical disc like BD is being played in low speed. But if the high-density optical disc is played in high speed, it is difficult to adopt the same extraction algorithm to data PLL and PRML architecture used in low speed application. It is because the signal with more than 800MHz should be processed in those architectures. Generally, in the 0.13-${\mu}m$ CMOS technology, it is necessary to have the high speed analog cores and lots of efforts to layout. In this paper, the parallel data PLL and PRML architecture, which enable to process in BD 8x speed of the maximum speed of the high-density optical disc as the extracting data and clock circuit, is proposed. Test results show that the proposed architecture is well operated without processing error at BD 8x speed.

• Tunnel and Underground Space
• /
• v.22 no.2
• /
• pp.144-156
• /
• 2012

This paper discusses the methods of estimating the punch penetration indices and data analysis punch penetration test to estimate the TBM normal force and penetration rate. In punch penetration test is known as a useful test to estimate penetration rates and normal force of TBMs directly with several slope indices indicated drill-ability and brittleness of rocks. However, the standard methods and indices for punch penetration test are not suggested yet. The main purpose of punch penetration test which is prediction of normal force of TBM disc cutter when cutters excavate rock mass. In this study, the punch penetration tests were performed for 6 representative Korean rock types and variety length and diameter of rock core specimens. Among slope indices were obtained from punch penetration test, PLI and MLI which is suggested in this study show high correlation with cutter force measured by full-scale cutting test. The results show that the predicted normal force of a single disc cutter and the experimental error was 10%. Based on these results, it is concluded that punch penetration test is reliable laboratory test for estimating thrust and penetration rates of TBM.

• Journal of Applied Biological Chemistry
• /
• v.43 no.1
• /
• pp.54-58
• /
• 2000

Methanol extracts of 27 Brazilian plant samples and 10 oriental medicinal plant samples (27 families), using spectrophotometric and paper disc agar diffusion methods under anaerobic conditions, were tested in vitro for their growth-inhibiting activities against Bifidobacterium longum, Bifidobacterium bifidum, Bifidobacterium adolescentis, Clostridium perfringens, and Bacteroides fragilis. The responses varied with bacterial strains, plant species, and tissues sampled. In a test with B. longum and B. bifidum(20 mg/disc), extracts of Acanthopanax sessilifolinus stem bark and Ampelozizyphus amazonicus leaves strongly inhibited the growth of B. longum, whereas other plant samples did not inhibit any intestinal bacteria tested. At 5 mg/disc, adding extracts of Aralia eleta, Euterpe oleracea, and Syzygium guineense to the media strongly inhibited the growth of C. perfringens and B. fragilis without growth inhibition of B. adolescentis, B. longum, and B. bifidum. Extracts of Jacaranda mimosifolia and Ulmus paraifolia significantly inhibited the growth of C. perfringens and B. fragilis as well as B. adolescentis. These results may be indications of at least one of the pharmacological actions of the five Brazilian plants but not oriental medicinal plants tested.