• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1161-1161
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• 2001

Rapid cost-effective methods of measuring wood quality are extremely important to tree improvement programs where it is necessary to test large numbers of trees. Non-destructive sampling of a forest can be achieved by using increment cores generally removed at breast height. At CSIRO Forestry and Forest Products methods for the rapid, non-destructive measurement of wood properties and wood chemistry based on increment core samples have been developed. In this paper the application of near infrared (NIR) spectroscopy to the prediction of a range solid wood properties, including density, longitudinal modulus of elasticity (E$\sub$L/) and microfibril angle (MFA), is described. Experiments conducted on individual species (Eucalyptus delegatensis and Pinus radiata), the two species combined and a number of mixed species from several genera are reported. NIR spectra were obtained from the radial/longitudinal face of each sample and used to develop calibrations for the measured physical properties. When the individual species were used the relationships between laboratory determined data and NIR fitted data were good in all cases. Coefficients of determination (R$^2$) ranging from 0.77 for MFA to 0.93 for stick density were obtained for E. delegatensis and R$^2$ ranging from 0.68 for MFA to 0.94 for strip density were obtained for P. radiata. The calibration statistics for the combined E. delegatensis and P. radiata samples were similar to those found for the individual species. As these results indicated that it might be possible to produce general calibrations based on samples from a number of species of a single genus or samples from a number of different genera, a wide range of species was subsequently tested. Good relationships were obtained for both density and E$\sub$L/. These calibrations had R$^2$ that were slightly lower than those determined using individual species and standard errors that were higher. The mixed species calibrations, when applied to the E. delegatensis and P. radiata sample sets, provided good estimates of density (stick and strip) and E$\sub$L/. The results demonstrated that a mixed species calibration, that encompasses wide variation in terms of, wood anatomy, chemistry and physical properties, could be used to rank trees. Experiments reported in this paper demonstrate that solid wood properties can be estimated by NIR spectroscopy. The method offers a rapid and non-destructive alternative to traditional methods of analysis and is applicable to large-scale non-destructive forest resource assessment, and to tree breeding and silvicultural programs.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.199-208
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• 2010

A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

• Journal of Preventive Medicine and Public Health
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• v.28 no.1 s.49
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• pp.225-243
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• 1995

Benzidine Industry in Korea has started after Japan has banned its production in early 1970's, and it has been in operation in Korea for over 20 years. However, it is not known yet whether any bladder cancer has developed from benzidine exposure. This study was done to screen benzidine-exposed workers for bladder cancer, and to examine the feasibility of employing screening test at the workplace. All the workplaces that manufacture or use benzidine for more than 20 years in Korea have been covered in this study, and they include 2 benzidine manufacturing factories, 5 benzidine using factories, as well as 2 benzidine free factories as an outside control. In total, 516 workers were screened with urine stick test and urine cytology test for the evidence of hematuria and abnormal urothelial cells. Each worker was also asked about risk factors and symptoms of bladder cancer including past medical history, smoking, medication and occupational history Benzidine in the air was measured by personal and area sampling. Out of 516 screened workers, 84(16.3%) workers showed positive hematuria in urine stick test, and 7(1.4%) workers showed degenerative cells in urine cytology tests. Those workers with abnormal urine test results who have been exposed to benzidine fo more than 10 years were further screened, and, in total, 23 workers were examined with intra-venous pyelography and cystoscopy. None of those screened had any evidence of bladder cancer When workers with only past hematuria history were included in the positive hematuria group, 96(18.5%) had positive hematuria. On the multiple logistic regression analysis, positive hematuria was significantly associated with benzidine exposure, history of other occupations with elevated bladder cancer risk, pyuria and glycosuria. The association got stronger as direct benzidine exposure was accounted through individual task analysis, and as exposure duration was accounted with tenure analysis. For those with benzidine exposure with more than 10 years of tenure, the odds of having positive hematuria was elevated 2.14(95%C.I is 1.08 to 4.25) times more than for those without exposure. Even though bladder cancer was not detected for several limitations including short observation period, majority of studied workers with short latency, healthy worker effect, and low sensitivity of single screening test in a cross-sectional study, the study results suggest that hematuria screening is a feasible and very useful test for bladder cancer screening among benzidine exposed workers.

• Restorative Dentistry and Endodontics
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• v.28 no.5
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• pp.378-384
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• 2003

This study evaluated the influence of a desensitizer(MS coat) on microtensile bond strength of different adhesives:a three-step adhesive(All-Bond 2), a two-step adhesive(Single Bond), a one-step adhesive(One-up Bond F). Non-caries extracted human molars were used. Dentin surface was obtained by horizontal section on mid-portion of crown using a water-cooled low speed diamond saw. Teeth were randomly divided into 6 group. AMO(MS coat + All Bond), SMO(MS coat + Single Bond)- and OMO(MS coat + One-up Bond F)-dentin surface were treated with 17% EDTA before bonded adhesive. AMX-, SMX- and OMX-dentin surface were bonded with All-Bond 2, Single Bond and One-up Bond F, respectively. with no previous treatment with MS coat and 17% EDTA. About 1cm high resin composite($Z-250^{TM}$) were incrementally build-up on the treated surface. The specimens for the microtensile test were serially sectioned perpendicular to the adhesive layer to obtain $0.7{\times}0.7mm$ sticks. 30 sticks were prepared from each group. After that. tensile bond strength for each stick was measured with Microtensile Tester at a 1mm/min crosshead speed. Fractured dentin surfaces were observed under the SEM. The results were statistically analysed by using a One-way ANOVA and Tukey's test(p<0.05). Value in MPa were: $AMO-44.35{\pm}13.21;{\;}SMO-39.35{\pm}13.32;{\;}OMO-31.07{\pm}10.25;{\;}AMX-49.22{\pm}16.38;{\;}SMX-56.02{\pm}13.35;{\;}OMX-72.93{\pm}16.19$. Application of MS coat reduced microtensile bond strengths of both Single Bond and One-up Bond F, whereas microtensile bond strengths of All-Bond 2 were not affected significantly.

• Composites Research
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• v.16 no.4
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• pp.44-50
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• 2003

The damage zone around a crack tip occurring before the fracture is a significant domain. which affects the toughening mechanism of materials. In this study. the growth process of damage zone in the vicinity of crack tip for rubber-modified epoxy resin is investigated using an acoustic emission(AE) analysis. The weight fractions of rubber(CTBN 1300$\times$B) in rubber-modified epoxy resin are 5 wt% and 15 wt%. The fracture toughness($K_{IC}$) and the fracture energy($G_{IC}$) were measured using 3 point bending single-edge notched specimens. The damage zone and rubber particles distributed around the crack tip were observed by a polarized optical microscope and an atomic force microscope(AFM). The damage zone around crack tip of rubber-modified epoxy resin was formed at 13 % loading and developed until 57 % loading of the fracture load. The crack initiated at 57 % loading grew repeatedly in the stick-slip propagation behavior. Based on time-frequency analysis, it was confirmed that AE signals with frequency bands of 0.15~0.20 MHz and 0.20~0.30 MHz were generated from cavitation and stable/unstable cracking inside the damage zone.

• Applied Microscopy
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• v.31 no.3
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• pp.245-256
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• 2001

The morphological characteristics of spermatogenic cells during the spermiogenesis of Paradoxornis webbiana were studied by transmission electron microscope. Spermiogenesis of P. webbiana was divided into ten phase. The chromatin granules became fibrous granules at the Golgi phase, gradually condensed at the cap phases, condensed as a stick at the acrosomal phase, and finally, a perfect nucleus was formed at the maturation phase. The formation of sperm tail began at the early Golgi phase, and completed at the late maturation phase. In particular, the dense materials existed in the sperm neck, which is wedged between the tip of segmented columns and the first mitochondria of the middle piece. The axone in the neck were surrounded by the dense materials. The axonema in spermatozoon contains a 9+2 arrangement of microtubules: 9 doublets, and 2 central single microtubules. Mitochondrial bundles of middle piece were composed of a pair of arms, which surrounded the axone of the middle piece by the $15^{\circ}$ angled-helical structure. The outer membrane of mitochondria were surrounded by microtubules in plasma membrane of the sperm. The undulating membrane had a helical structure, and the sperm plasma membrane was surrounded by undulating membrane.

• The Journal of the Korea Contents Association
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• v.8 no.11
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• pp.85-93
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• 2008

For music score recognition, several approaches have been proposed including shape matching, statistical methods, neural network based methods and structural methods. In this paper, we deal with recognition for low resolution images which are captured by the digital camera of a mobile phone. Considerable distortions are included in these low resolution images, so when existing technology is used, many problems appear. First, captured images are not stable in the sense that they contain lots of distortions or non-uniform illumination changes. Therefore, notes or symbols in the music score are damaged and recognition process gets difficult. This paper presents recognition technology to overcome these problems. First, musical note to head, stick, tail part are separated. Then template matching on head part of musical note, and remainder part is applied. Experimental results show nearly 100% recognition rate for music scores with single musical notes.

• Korean Journal of Ichthyology
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• v.25 no.1
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• pp.46-49
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• 2013

A single specimen (373.2 mm SL) of the snailfish Careproctus colletti was collected by gill-net at Donghae-si, East Sea, Korea. This species is characterized by having the slender and stick-like teeth, lower end of gill opening not reaching to upper origin of pectoral fin, rays of lower part of pectoral fin long, reaching behind anus and margins of dorsal and anal fin dark. We described it as the first record to Korean fish fauna, and proposed the new Korean name "Meok-bun-hong-kkom-chi" for this species.

• Restorative Dentistry and Endodontics
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• v.29 no.2
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• pp.153-161
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• 2004

This study investigated that the effect of rewetting agent on dentinal microtensile bond strength(${\mu}TBS$). Human molars were sectioned to expose the superficial dentin surfaces. Samples were divided into two groups according to type of adhesives-Single Bond (S) and One-Step (0)], and again subdivided into five groups by different dentin surface treatment-dry for 15s (D), blot dry (BD) or dry for 15s, and rewet with different rewetting agents [distilled water (DW), Gluma Desensitizer (GD) and Aqua-Prep (AP)] for 30s. After application of adhesive, composite resin was built up on the bonding surface. Each tooth was sectioned to obtain stick with $1\textrm{mm}^2$ cross sectional area and the ${\mu}TBS$ was determined by EZ test. In the S group, the mean ${\mu}TBS$ of GD, AP, and BD group was significantly higher than that of DW and D group (p < 0.05), In the O group, the mean, ${\mu}TBS$ of AP, GD, BD and DW group was significantly higher than that of D group (p < 0.05). The data suggested that Gluma Desensitizer and Aqua-Prep could be successfully used as rewetting agents, and Distilled water could be acceptable in aceton based adhesive system only.

• Tribology and Lubricants
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• v.37 no.6
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• pp.261-272
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• 2021

This study investigates the structural characteristics of oil-free, gas beam foil journal bearings (GBFJBs) for use in high speed motors. Mathematical modeling was carried out, and reaction force modeling for static load was performed to predict the structural characteristics of the GBFJB. Mathematical modeling and reaction force modeling for static load are performed to predict the structural characteristics of GBFJBs. The reaction force of the test bearing against static loads was measured during experiments and compared with the predicted results. The measured experimental data reveal the nonlinear stiffness characteristics of the GBFJB against varying displacement and agree well with the predictions. Dynamic load tests using an exciter allow to identify the vibration characteristics of the GBFJB. Test results show that the vibration displacement, dynamic force, and acceleration measured on the test bearing are most dominant at the applied dynamic load (synchronization) frequency. Futhermore, the test results show that the hysteresis area recorded during the dynamic tests increases with the excitation amplitude and frequency, and that the beam stick phenomena occurr at high excitation frequencies. The single degree of freedom (DOF) vibration model aids to identify the stiffness and damping coefficient of the GBFJB, which decrease as the excitation frequency increases.