• Geophysics and Geophysical Exploration
• /
• v.16 no.2
• /
• pp.79-90
• /
• 2013

Geophysical investigation in non-destructive testing is economically less expensive than boring testing and providing geotechnical information over wide-area. But, it provides only limited geotechnical information, which is hardly used to the design. Accordingly, we performed electrical resistivity experiments on large scale of soil model to analyze the correlation between electrical resistivity response and soil water contents. The soils used in the experiments were the Jumunjin standard sand and weathered granite soil. Each soil particle size distribution and coefficient of uniformity of experimental material obtained in the experiments were maintained in a state of the homogeneous. The specifications of the model used in this study is $160{\times}100{\times}50$(cm) of acrylic, and each soil was maintained at the height 30 cm. The water content were measured using the 5TE sensors (water contents sensors) which is installed 7 ~ 8 cm apart vertically by plugging to floor. The results of the resistivity behavior pattern for Jumunjin standard sand was found to be sensitive to the water content, while the weathered granite soil was showing lower resistivity over the time, and there was no significant change in behavior pattern observed. So, it results that the Jumunjin standard sand's particle current conduction was better than the weathered granite soil's particle through contact with the distilled water. This lab test was also compared with the result of a test bed site composed of similar weathered soil. It was confirmed that these experiments were underlying research of non-destructive investigation techniques to improve the accuracy to estimate the geotechnical parameter.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.6
• /
• pp.597-603
• /
• 2012

It is necessary to accurately evaluate the resistance performance and estimate the towing power of a tugboat for safety towing operation at actual seas. In this study, we have carried out the model tests firstly to investigate the resistance performance and flow characteristics around the tugboat in still water. The experiments are performed in infinite depth in circulation tank using 1/33.75 scaled model from 5kts to 10kts(designed speed 7kts) considering the effect of adverse and favorable current. Then the numerical calculations are executed to analyze the response amplitude operator and added resistance on tugboat due to the waves. The results obtained by the present computation are compared with the those acquired from the experiments in still water. As a result, it is noted that the added resistance become larger at head sea and higher speed conditions. We can also observe that the EHP increase 70 percent in comparison with those in still water.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.4
• /
• pp.567-574
• /
• 2006

This paper focuses on lossy medical image compression methods for medical images that operate on three-dimensional(3-D) irreversible integer wavelet transform. We offer an application of unbalanced tree structure algorithm to medical images, using a 3-D unbalanced wavelet decomposition and a 3-D unbalanced spatial dependence tree. The wavelet decomposition is accomplished with integer wavelet filters implemented with the lifting method. We have tested our encoder on volumetric medical images using different integer filters and 16 coding unit size. The coding unit sizes of 16 slices save considerable dynamic memory(RAM) and coding delay from full sequence coding units used in previous works. If we allow the formation of trees of different lengths, then we can accomodate more transaxial scales than three. Then the encoder and decoder can then keep track of the length of the tree in which each pixel resides through the sequence of decompositions. Results show that, even with these small coding units, our algorithm with I(5,3)filter performs as well and better in lossy coding than previous coding systems using 3-D integer unbalanced wavelet transforms on volumetric medical images.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.6
• /
• pp.290-297
• /
• 2014

The synchronization of OFDM receiver is consisted of symbol timing offset(STO) estimation in time domain and carrier frequency offset(CFO) estimation in frequency domain. This paper proposes new algorithm for correcting the integer CFO after we have done correcting the STO and partial CFO. ICFO must be corrected, since the ICFO lead to degrade bit error rate(BER) of demodulation performance. The PN sequence has information which is subcarrier order since the modified PN sequence, length is same subcarrier, is used in this paper and is modulated each subcarrier by each chip. Thus the receiver track phase of PN sequence after FFTin order to find the subcarrier frequency offset. The proposed algorithm is faster and more simple than convenient methode as measuring carrier energy.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.4
• /
• pp.43-53
• /
• 2003

To get improved soil parameters in the laboratory tests, the effects of sample disturbance should be excluded as much as possible. A collaborative research between Dong-A University and PHRI (Japan) was conducted to investigate the effects of sample disturbance due to sampling techniques and samplers on Pusan clays. The results of unconfined compression and consolidation tests performed on the clay samples taken by them have been compared in terms of soil parameters and sample disturbance. As the result of the study, it was found that when the Korean sampler was used with a different technique of cleaning the borehole bottom and removing slime before inserting and penetrating the sampler tube, similar to the one commonly used in Japanese practice, the quality of samples could be greatly improved. Furthermore, the CRS test with the rate of 0.02%/min yielded larger values of consolidation parameters and better degree of sample disturbance than those of oedometer test, due to the difference in testing method.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.3
• /
• pp.115-123
• /
• 1989

This paper probabilisticly analyses the variance of the soil parameters on kinds of soil by conducting statistical analysis through the Unified Soil Classification System. Data used are the result of soil test which the Korea National Housing Corporation conducted in 176 sites of 74 cities throughout the country during the past 13 years from 1974 to 1986. In this paper, soil parameters such as natural water contents, specific gravity of soil particle, Atterberg limits, N-values, unconfined compression strength, compression index and shear strength parameter etc., is analysed. The result of the analysis is as follows. 1) The variance in physical properties of the soil is, when compared with coefficient of variation which is statistical variable, comparatively small. 2) The shear strength parameter is proved to be about 40% and compression index is about 32%. 3) The variance in specific gravity is 0.87-2.49% in granular soil and 0.91~5.03% in cohesive soil respectively. So, the degree of the variance is very small.

• Journal of the Korea Institute of Building Construction
• /
• v.21 no.4
• /
• pp.305-318
• /
• 2021

The aim of the research is providing the rheological performance range for manufacturing "mid-workability concrete". The mid-workability concrete means the normal strength range concrete mixture with high workability. Since there is not enough study or quantitative definitions on performance of the mid-workability concrete, in this research, the performance range for high workability of mid-workability concrete mixture using rheology. Because of the mixture characteristics of generally used normal strength concrete such as relatively high water-to-cement ratio and no SCMs, segregation of coarse aggregate should be prevent to achieve a successful high workability. From the experimental study in this research scope, 5 to 35 Pa.s of plastic viscosity was desirable to prevent segregation for nid-workability concrete, and general performance range with rheological parameters was provided.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.2C
• /
• pp.81-88
• /
• 2006

This study performed field and laboratory tests for poor subsoils taken in six regions of the country and determined undrain shear strength. Su values and preconsolidation pressure are predicted using Back Propagation neural network (BPNN) and the application of BPNN is verified. The result of BPNN shows that correlation coefficient between test and neural network result is over 0.9, which means high correlativity. Especially the neural network uses only 6 parameters such as natural water content, void ratio, specific gravity, rate of passing 200th sieve, liquid limits and plasticity index among various affecting factors to estimate value and the correlation coefficent is 0.93. The conclusions obtained in this paper are from the tests performed for poor subsoils taken in the several regions of the country. If there were more test results, the prediction and influence of various soil properties could be effectively performed by neural network.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.5A
• /
• pp.484-489
• /
• 2007

The main disadvantage of orthogonal frequency division multiplexing (OFDM) systems is its sensitivity to carrier frequency offset and timing offset. This paper proposes a simple way of improving the performance of the integer frequency offset (IFO) estimator in OFDM-based digital video broadcasting (DVB) system. By modifying the conventional maximum likelihood (ML) estimator to have multi-stage estimation strategy, IFO estimator is derived. Simulations indicate that the proposed IFO estimator works robustly with reduced computational burden when compared to ML estimator.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.414-417
• /
• 2003

A copper-clad aluminium composite bar is lighter and less expressive than a commercial copper alloy bar. Copper-clad aluminium composite bar can be fabricated by hot hydrostatic extrusion process. In this work, the effect of die angle on the compressive properties of copper-clad aluminium composites fabricated using hydrostatic extrusion process was investigated experimentally. The results showed that optimum half die angle was in the range of 40$^{\circ}$ to 50$^{\circ}$ for an extrusion ratio of 19. The results also showed that the half die angle had little influence on the compressive strength of copper-clad aluminium composites. A diffusion layer increased with increasing die angle.