• Journal of Internet Computing and Services
• /
• v.8 no.3
• /
• pp.33-43
• /
• 2007

In this proper, we proposes a robust watermarking against the lossy compression in the Hadamard domain. The Hadamard matrix consists of only 1 or -1 and can be computed veru fast. The Hadamrd transform has the inverse transform therefore it is able to be applied into the watermarking technology. In embedding process, we select 10 coefficients from intermediate frequency domain and create two watermark patterns. In extraction process, we use the watermark patterns and compare them to detect the watermark information. When we use the standard image ($512{\times}512$) and binary watermark image ($64{\times}64$), the results of these examines are PSNR for $38{\sim}42dB$ and BER for $3.9{\sim}12.5%$. The JPEG QF between 30 and100, naked human eyes can detect to watermark image easily. The experimental results show that performance of Hadamard domain is better than those of DCT, FFT, and DWT.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.40 no.4
• /
• pp.344-350
• /
• 2004

This is the study on dry sliding wear behavior of unidirectional carbon fiber reinforced epoxy matrix composite at ambient temperature. The wear rates and friction coefficients against the stainless steel counterpart specularly processed were experimentally determined and the resulting wear mechanisms were microscopically observed. Three principal sliding directions relative to the dominant fiber orientation in the composite wear selected. When sliding took place against smooth and hard counterpart, the highest were resistance and the lowest friction coefficient were observed in the antiparallel direction. When the velocity between the composite and the counterpart went up, the wear rate increased. The fiber destruction and cracking caused fiber bending on the contact surface, which was discovered to be dominant wear mechanism.

• Asian-Australasian Journal of Animal Sciences
• /
• v.31 no.1
• /
• pp.86-90
• /
• 2018

Objective: This study was conducted to investigate the effects of dietary detoxified Rhus verniciflua sap (RVS) on production performance, egg quality, lipid fractions of egg yolk, liver and serum, and the profile of cecal microflora in laying hens. Methods: Two hundred 52-week-old Hy-Line Brown layers were randomly divided into 4 groups with 5 replicates per group (2 hens per cage, 5 cages per replicate) and were provided with one of 4 experimental diets containing 0%, 0.05%, 0.1%, or 0.2% RVS, for 6 weeks. Due to unequal intervals of RVS doses, the interactive matrix language procedure of the SAS program was used to correct the contrast coefficients of orthogonal polynomials. Results: There were no differences in feed intake and egg weight among the groups. Egg production increased (linearly and quadratically, p<0.05) with increasing levels of RVS. Eggshell thickness increased (linear, p<0.05) as the level of RVS in diets increased. The levels of blood cholesterol and activities of glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase were not altered by dietary treatments. Increasing level of RVS increased (linear, p<0.05) the populations of cecal lactic acid bacteria. The content of yolk cholesterol decreased (linear, p<0.05) with increasing levels of dietary RVS, although there were no significant differences in each lipid fraction of the liver. Conclusion: This study indicates that dietary RVS could improve laying performance and eggshell quality, and affect cecal lactic acid bacteria in a dose-dependent manner.

• Journal of the Korean Chemical Society
• /
• v.45 no.5
• /
• pp.429-435
• /
• 2001

The monomer N,N'-bis(2-pyrrol-1-yl-propyl)-4,4'-bipyridine(bpb) was electrochemically polymerized on the glassy carbon electrode surface, which was modified with 1:1 ratio of erichrome black T(EBT) and glutathione(GSSG) to give a type of GC/poly-bpb, EBT, GSSG electrode for depositing Zn(II). The diffusion coefficients of the incorporated ions were 2.43${\times}10^{-15}$ and 9.14${\times}10^{-15} cm^2s^{-1}$ before taking Zn(II) ions and after them respectively. The modified electrodes are stable at the electrode process. The polymerized poly-bpb of 2.83${\times}10^4gmol^{-1}$ can deposit 2.15${\times}10^4gmol^{-1}$ of Zn(II). The number of pumping ions involving in the redox procedure at 0.77 V was 81.7% of the captured 180 ions into the polymer matrix, which was 3 times larger than that of the electrode modified with EBT alone.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.10C
• /
• pp.1000-1010
• /
• 2006

This paper proposes a new architecture for DCT-based motion estimation and compensation. Previous methods do riot take sufficient advantage of the sparseness of 2-D DCT coefficients to reduce execution time. We first derive a recursion equation to perform DCT domain motion estimation more efficiently; we then use it to develop a wavefront array processor (WAP) consisting of processing elements. In addition, we show that the recursion equation enables motion predicted images with different frequency bands, for example, from the images with low frequency components to the images with low and high frequency components. The wavefront way Processor can reconfigure to different motion estimation algorithms, such as logarithmic search and three step search, without architectural modifications. These properties can be effectively used to reduce the energy required for video encoding and decoding. The proposed WAP architecture achieves a significant reduction in computational complexity and processing time. It is also shown that the motion estimation algorithm in the transform domain using SAD (Sum of Absolute Differences) matching criterion maximizes PSNR and the compression ratio for the practical video coding applications when compared to tile motion estimation algorithm in the spatial domain using either SAD or SSD.

• Computers and Concrete
• /
• v.26 no.1
• /
• pp.75-94
• /
• 2020

The aim of this research is to investigate free vibration of a novel five layer Timoshenko microbeam which consists of a transversely flexible porous core made of Al-foam, two graphen platelets (GPL) nanocomposite reinforced layers to enhance the mechanical behavior of the structure as well as two piezo-magneto-electric face sheets layers. This microbeam is subjected to a thermal load and resting on Pasternak's foundation. To accomplish the analysis, constitutive equations of each layer are derived by means of nonlocal strain gradient theory (NSGT) to capture size dependent effects. Then, the Hamilton's principle is employed to obtain the equations of motion for five layer Timoshenko microbeam. They are subsequently solved analytically by applying Navier's method so that discretized governing equations are determined in form of dynamic matrix giving the possibility to gain the natural frequencies of the Timoshenko microbeam. Eventually, after a validation study, the numerical results are presented to study and discuss the influences of various parameters such as nonlocal parameter, strain gradient parameter, aspect ratio, porosity, various volume fraction and distributions of graphene platelets, temperature change and elastic foundation coefficients on natural frequencies of the sandwich microbeam.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.9 no.5
• /
• pp.552-567
• /
• 2017

The floating crane vessel in waves gives rise to the motion of the lifted object which is connected to the hoisting wire. The dynamic tension induced by the lifted object also affects the motion responses of the floating crane vessel in return. In this study, coupled motion responses of a floating crane vessel and a lifted subsea manifold during deep-water installation operations were investigated by both experiments and numerical calculations. A series of model tests for the deep-water lifting operation were performed at Ocean Engineering Basin of KRISO. For the model test, the vessel with a crane control system and a typical subsea manifold were examined. To validate the experimental results, a frequency-domain motion analysis method is applied. The coupled motion equations of the crane vessel and the lifted object are solved in the frequency domain with an additional linear stiffness matrix due to the hoisting wire. The hydrodynamic coefficients of the lifted object, which is a significant factor to affect the coupled dynamics, are estimated based on the perforation value of the structure and the CFD results. The discussions were made on three main points. First, the motion characteristics of the lifted object as well as the crane vessel were studied by comparing the calculation results. Second, the dynamic tension of the hoisting wire were evaluated under the various wave conditions. Final discussion was made on the effect of passive heave compensator on the motion and tension responses.

• Transactions of Materials Processing
• /
• v.24 no.1
• /
• pp.44-51
• /
• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.7 no.1
• /
• pp.128-141
• /
• 2015

Independent Component Analysis (ICA), one of the blind source separation methods, can be applied for extracting unknown source signals only from received signals. This is accomplished by finding statistical independence of signal mixtures and has been successfully applied to myriad fields such as medical science, image processing, and numerous others. Nevertheless, there are inherent problems that have been reported when using this technique: instability and invalid ordering of separated signals, particularly when using a conventional ICA technique in vibratory source signal identification of complex structures. In this study, a simple iterative algorithm of the conventional ICA has been proposed to mitigate these problems. The proposed method to extract more stable source signals having valid order includes an iterative and reordering process of extracted mixing matrix to reconstruct finally converged source signals, referring to the magnitudes of correlation coefficients between the intermediately separated signals and the signals measured on or nearby sources. In order to review the problems of the conventional ICA technique and to validate the proposed method, numerical analyses have been carried out for a virtual response model and a 30 m class submarine model. Moreover, in order to investigate applicability of the proposed method to real problem of complex structure, an experiment has been carried out for a scaled submarine mockup. The results show that the proposed method could resolve the inherent problems of a conventional ICA technique.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.18 no.3
• /
• pp.291-302
• /
• 2005

Due to the importance of the parameter in structural response, the uncertain elastic modulus was located at the center of stochastic analysis, where the response variability caused by the uncertain system parameters is pursued. However when we analyze the so-called stochastic systems, as many parameters as possible must be included in the analysis if we want to obtain the response variability that can reach a true one, even in an approximate sense. In this paper, a formulation to determine the statistical behavior of in-plane structures due to multiple uncertain material parameters, i.e., elastic modulus and Poisson's ratio, is suggested. To this end, the polynomial expansion on the coefficients of constitutive matrix is employed. In constructing the modified auto-and cross-correlation functions, use is made of the general equation for n-th moment. For the computational purpose, the infinite series of stochastic sub-stiffness matrices is truncated preserving required accuracy. To demons4rate the validity of the proposed formulation, an exemplary example is analyzed and the results are compared with those obtained by means of classical Monte Carlo simulation, which is based on the local averaging scheme.