• Journal of Korea Foresty Energy
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• v.25 no.2
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• pp.9-15
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• 2006

The quality of wood is largely depend on the characteristics of xylem tissue and their variation. They may include tracheid length, microfibril angle, distribution and amount of resin canal, as well as specific gravity as indicator of material properties. In this study, variation of these elements between and within 30 superior families of Pinus densifloa in progeny test forest were examined and the results are as follows; In terms of elongation ratio of tracheid length which is less than 1%, the sample tree showed a transition to matured wood after 13 years particularly in Kangwon 25, 30, 90, 56 and Chungnam 4 families. The average specific gravity were from 0.35 to 0.49, and differences between the families were significant. Number of transverse resin canal per unit area were also found to be significant between the families. The microfibril angles measured at 15th ring number ranged from 0.9 degree to 28.6 degree. More studies are necessary to tell whether these variation is inherited by genetic or individual characteristic. However it would be desirable that these elements be considered as key elements in the early stage of selection process of superior tree to ensure good quality of wood production in future.

• Geotechnical Engineering
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• v.13 no.1
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• pp.111-122
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• 1997

The calculation of phase velocities in Spectral-Analysis -of-Surface -Waves (SASW) meas urements requires unwrapping phase angles. In case of layered systems with strong stiffness contrast like a pavement system, conventional phase unwrapping algorithm to add in teger multiples of 2n to the principal value of a phase angle may lead to wrong phase volocities. This is because there is difficulty in counting the number of jumps in the phase spectrum especially at the receiver spacing where the measurements are in the transition Bone of defferent modes. A new phase interpretation scheme, called "Impulse Response Fil traction ( IRF) Technique," is proposed, which is based on the separation of wave groups by the filtration of the impulse response determinded between two receivers. The separation of a wave group is based on the impulse response filtered by using information from Gabor spectrogram, which visualizes the propagation of wave groups at the frequency -time space. The filtered impulse response leads to clear interpretation of phase spectrum, which eliminates difficulty in counting number of jumps in the phase spectrum. Verification of the IRF technique was performed by theoretical simulation of the SASW measurement on a pavement system which complicates wave propagation.opagation.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.231-237
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• 2005

The sizes and structure of micelles and vesicles formed in ammonium dodecyl sulfate (ADS)/octadecyl trimethyl ammonium chloride (OTAC) mixed aqueous solutions were analyzed by small-angle neutron scattering. In micellar regions of pure ADS and OTAC aqueous solution, the spherical micelles were formed at given concentrations and their sizes were 40 and $61{\AA}$, respectively. The structure transition of pure micelles occurred above 300 mM due to the constancy of the intermicellar distance above 250 mM. The coexisting region of mixed micelles and vesicles in phase diagram of mixed system was also assured. It was investigated that vesicle formed spontaneously took a bilayer structure. The lamellar thickness of vesicles decreased with increasing concentration of vesicle samples. However, the size could not be determined for mixed micelle and vesicle above 100 nm due to limitation of low q ranges. Finally, The 9 mM solution of ADS mole fraction 0.9 (${\alpha}$=0.9) showed bilayer structure compared to phase diagram classified into mixed micelle.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.105-113
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• 2009

The interpretation of observed waveform characteristics identified in refraction and wide-angle reflection data increases confidence in the crustal structure model obtained. When calculating traveltimes and raypaths, wavefront methods on a regular grid based on graph theory are robust even with complicated structures, but basically compute only first arrivals. In this paper, we develop new algorithms to compute traveltimes and raypaths not only for first arrivals, but also for fast and later reflection arrivals, later refraction arrivals, and converted waves between P and S, using the modified wavefront method based on slowness network nodes mapped on a multi-layer model. Using the new algorithm, we can interpret reflected arrivals, Pg-later arrivals, strong arrivals appearing behind Pn, triplicated Moho reflected arrivals (PmP) to obtain the shape of the Moho, and phases involving conversion between P and S. Using two models of an ocean-continent transition zone and an oceanic ridge or seamount, we show the usefulness of this algorithm, which is confirmed by synthetic seismograms using the 2D Finite Difference Method (2D-FDM). Characteristics of arrivals and raypaths of the two models differ from each other in that using only first-arrival traveltime data for crustal structure analysis involves risk of erroneous interpretation in the ocean-continent transition zone, or the region around a ridge or seamount.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.914-921
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• 2017

The experimental research on a high-altitude environment simulation of space launch vehicle is important for securing independent technologies with launching space vehicles and completing missions. This study selected an altitude of 65 km for the experiment environment where it exceeded Mach number of 6 after the launch of Korean Space Launch Vehicle(KSLV-II). Shock tunnel was used to replicate the flight condition. After flow establishment, in order to confirm aerodynamic characteristics and normal and oblique shockwaves, the flow verification was carried out by measuring stagnation pressure and heat flux of a forebody model, and shockwave stand-off distance of a hemispherical model. In addition, a shock-free technique to recover free-stream condition has been developed and verified. From the results of the three verification tests, it was confirmed that the flow was replicated with the error of about ${\pm}3%$. The error between the slope angle of inclined shockwave of the scaled down transition section model using the shock-free shape and the slope angle of the horizontal plate model, and between the theoretical and the experimental value of the static pressure of the model were confirmed to be 2% and 1%, respectively. As a result, the efficiency of the shockwave cancellation technique has been verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.737-742
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• 2016

We prepared five different ethylene-propylene copolymers (EPCs) for use as the encapsulant of a photovoltaic module. All of the polymers were of commercial grade from ExxonMobile company and had different ethylene/propylene compositions. The crystallization behaviors and crystal structures of the polymers were analyzed by differential scanning calorimetry and wide angle X-ray scattering diffractometry, respectively. We observed the general trend that the degree of crystallization, density and glass transition temperature of the EPCs decreased with increasing ethylene content. However, an unexpected result was also observed: the EPC with the highest ethylene content (22.2 mol. %) showed the highest melting temperature. As a result, the EPC with 22.2 mol. % of ethylene shows the highest light transmittance, due to its having the lowest degree of crystallization and highest thermal creep resistance. This abnormal result is attributed to the blocky structure prepared by ExxonMobile's special catalyst technology. It was also observed that new additional melting peaks appeared as the crystallization time increased. Using wide angle X-ray scattering diffractometry, it was confirmed that these additional peaks originated from the formation of a new crystal structure caused by annealing.

• The Journal of the Korea Contents Association
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• v.12 no.12
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• pp.335-344
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• 2012

Osteoporosis is increasing in Korea as it becomes an aging society with the rapid economic growth and the development of medical technology. Osteoporosis also develops due to chemo and radiation therapy of cancer which also increases owing to Westernized diet. Osteoporosis is caused by reduced bone density, has close relationship with the change of geometry of proximal femur, which is a factor of hip fracture risk. The purpose of this study was the analysis of the correlations of osteoporosis and the change of geometry of proximal femur, which was observed according to T-score variance. The 350 male and female patients are chosen from D hospital in Busan, who were classified by age, sex and T-score values (normal, osteopenia, and osteo porosis). The results show that the age and gender have significant difference in the incidence of osteoporosis; the disease classification according to T-score value has significant difference in the geometry of the proximal femur such as Cortical ratio calcar, Cortical ratio shaft, Hip/shaft Angle, Strength index, Section modulus, CSMI, and CSA, and is highly correlated with the incidence of osteoporosis. Therefore, the findings of this research is that the change of the geometry of the proximal femur could be used as an indicator in the diagnosis of osteoporosis, could enhance the accuracy of the diagnosis in the future, and could be used as a clinical predictive factors through the analysis of the correlations of T-score variance and the geometry changes of the proximal femur.

• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.247-253
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• 2016

Ultrasound devices diagnose many disease, which is widely used, can not be standardized quantitative evaluated in order to evaluate sonography image of quality. Therefore, in this papers, aims to get correct image in order to accurate diagnosis by figuring out the appropriate parameter based on each target by measuring distortion which results in the analyzation of the sensitivity of SNR and the histogram of signal by manipulating parameter of 8 mm target in ATS-539 multipurpose phantom. Equipment using Acuson sequoia 512, convex probe and utilizes multi-objective phantom. experiment method is that first you put the phantom on the flat and acquire 85 sheets of image, changing frequency(2,3,4 MHz, harmonic 3, 4, 4.5 MHz), Focus(2, 4, 6 unit), and Dynamic Range(58, 68, 78, 88, 98) for a 8 mm structure. through the Image J program. The sensitivity angle of 8mm target through Image J program is gauged by each separate target SNR and the distorted angle subtract and measure Histogram of background from Histogram of signal and take top 40% from the given result value above. According to parameter variation we found out proper parameter by acquiring SNR of sensitivity and distortion data for aspect of transition. The more this findings have Focus, the lower distortion value and at 4 MHz frequency this result have high SNR and low distortion value. Dynamic Range got an appropriate image on 88 and 98. It is considered on the basis of the experimental data, the probability of disease diagnosis will get higher.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.585-592
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• 2016

Visualization was done by using $CH^*$ chemiluminescence images and PMT measurements in order to understand the origin of fluctuating pressure and chemical luminosity at about 500 Hz frequency even in stable combustion, which was observed in recent experimental tests, and to find the physical correlation leading to Low Frequency Instability(LFI) in terms of phase angle. In stable combustion, chemical reactions are distributed along the shear layer flow showing a negative coupling(about 180 degree in phase angle) with combustion pressure. However, phase difference is shifted to a positive coupling showing less than 90 degree in unstable case. Also a periodic change in the distribution of chemical reactions is observed along with local flame extinction and the appearance of big scale vortex flow. In the transition to LFI, local flame extinction and small vortex flow start to appear in a row. As seen in the bluff body wake in reactive flow, the periodic appearance of vortex flow seems to share the same physical process of BVK(Bernard Von Karman) instability generation. Thus, the appearance of local extinction in 500 Hz fluctuations is gradually amplified to complete extinctions of about 20 Hz, and it leads into LFI.

• Polymer(Korea)
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• v.33 no.4
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• pp.319-325
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• 2009

The solution polymerization was conducted to synthesize pressure sensitive adhesive for polarizer film using acrylic monomers. 2-Ethylhexylacrylate, butylacrylate, acrylic acid were used as acrylic monomers. The ratio was 2-ethylliexylacrylate:butylacrylate:acrylic acid=25:50:3.6 by reflecting $-40^{\circ}C$ of glass transition temperature in the pressure sensitive adhesive. When 1 wt% of coupling agent was added to the polymerized pressure sensitive adhesive, the light transmissivity was significantly increased. This result is due to the enhancement of adhesive power against liquid crystal cell by Si-O bond of coupling agents. Cross-linking agent was added by 0.5, 1.0, and 1.5 wt% with respect to the synthesized polymer. Initial tackiness decreased, while cohesion increased with increasing crosslinking agent. In the analysis of contact angle, the increase of crosslinking agents yielded the enhancement of surface energy, resulting in the decrease of contact angle. From the measurement of heat resistance, the acrylic pressure sensitive adhesive showed excellent heat resistance regardless of change in temperature and contents in crosslinking agent. In the observation of a cutting plane, the increased crosslinking agent represented a smoother and cleaner section. Comprehensively, the optimum additive amount of crosslinking agent was determined to be 1.0 wt% to monomer.