Natural Science University

Ho Chi Minh City, Vietnam

Natural Science University

Ho Chi Minh City, Vietnam

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Nguyen H.-B.,Nong Lam University | Trinh H.-L.,National University | Chau V.-T.,Natural Science University | Nguyen V.-T.,Natural Science University
Kerntechnik | Year: 2014

In this paper, the Hamiltonian theory of particle motion has been applied for developing the motion equations of electrons in linear accelerator of Iris-loaded waveguides. Using J. C. Slater asumption for determining electric field in Oz direction, the energy increase of electron in the guide wave pipe following the linacs resonance cavity with circulated electromagnetic distribution and repeat-cycle of given number of resonance cavities has been developed. The energy gain of electron following the electron way in Oz axle direction of the accelerator with the different injection phase and phase shift of RF has been obtained. The results indicate that the energy increase of electron depends on the injection phase of RF and cell-To-cell phase shift.


Chen W.-J.,Da - Yeh University | Chang C.-C.,Feng Chia University | Chang C.-C.,National Chung Cheng University | Le T.H.N.,Natural Science University
Expert Systems with Applications | Year: 2010

Steganography is the art and science of hiding data into information. The secret message is hidden in such a way that no one can apart from the sender or the intended recipient. The least significant bit (LSB) substitution mechanism is the most common steganographic technique for embedding a secret message in an image with high capacity, while the human visual system (HVS) would be unable to notice the hidden message in the cover image. In this paper, besides employing the LSB substitution technique as a fundamental stage, we take advantage of edge detection technique. The experimental results show that the proposed scheme not only achieves high embedding capacity but also enhances the quality of the stego image from the HVS by an edge detection technique. Moreover, based on that the secret message is replaced with different LSBs, our scheme can effectively resist the image steganalysis. © 2009 Elsevier Ltd. All rights reserved.


Thuc C.N.H.,University of Savoy | Thuc C.N.H.,Natural science University | Grillet A.-C.,University of Savoy | Reinert L.,University of Savoy | And 3 more authors.
Applied Clay Science | Year: 2010

Several granulometric treatments and chemical processes were tested to separate and purify montmorillonite (MMT) from the bentonite deposits of LamDong and ThuanHai (south and central Viet Nam) to obtain MMT for filler application in polymer nanocomposites. X-ray diffraction, laser granulometry, nitrogen adsorption at 77. K, cationic exchange capacity (CEC), and infra-red spectroscopy (IR) measurements showed that the purest fraction of MMT was separated from the raw material by sedimentation (55. h) combined with centrifugation and sonication, compared with a sonication coupled with sedimentation or a single centrifugation. The quartz impurities were totally removed by the more efficient granulometric separation whereas residual kaolinite particles were still observed by the IR spectra. The granulometric separation by sedimentation or centrifugation already tested on raw materials were also applied successfully on chemically purified LamDong bentonite sonicated in PEO (polyethylene oxide) aqueous solution, allowing the direct preparation of pure MMT/PEO intercalated compounds free from quartz impurities, suitable for filler application in polymer nanocomposites.The separated MMT (from LamDong or ThuanHai Clays) after granulometric separation was chemically purified by three steps: 1. the carbonates were dissolved with acetic acid; 2. organic molecules were oxidized by hydrogen peroxide; and 3. iron (hydr)oxides were removed by several complexation and redox reactions. The X-ray fluorescence (XRF) chemical analyses and X-ray microanalyses coupled with scanning electron microscopy (SEM) showed that the nitric acid and the dithionite-oxalic acid reaction were ways to remove the iron (hydr)oxides from the bentonites (respectively ~ 2 mass % and ~ 0.3 mass % iron content after purification). The combination of the four reactions involving successively complexation + reduction + acid reactions allowed to minimize the proportion of iron (hydr)oxides in the LamDong purified MMT (~ 1.5 mass % of Fe). © 2010 Elsevier B.V.


Le T.H.N.,Natural Science University | Lin C.-C.,Providence University | Chang C.-C.,Feng Chia University | Chang C.-C.,National Chung Cheng University | Le H.B.,Natural Science University
Digital Signal Processing: A Review Journal | Year: 2011

Many secret sharing schemes for digital images have been developed in recent decades. Traditional schemes typically must deal with the problem of computational complexity, and other visual secret sharing schemes come with a higher transmission cost and storage cost; that is, each shadow size is m times as big as the original secret image. The new (2,n) secret sharing scheme for grayscale images proposed in this paper is based a combination of acceptable image quality using block truncation coding (BTC), high compression ratio discrete wavelet transform (DWT) and good subjective performance of the vector quantization (VQ) technique. Experimental results confirm that our proposed scheme not only generates a high quality reconstructed original image but also generates small, random-like grayscale shadows. © 2011 Elsevier Inc. All rights reserved.


Chang C.-C.,Feng Chia University | Chang C.-C.,National Chung Cheng University | Lee J.-S.,Feng Chia University | Le T.H.N.,Natural Science University
Digital Signal Processing: A Review Journal | Year: 2010

Data hiding technique can facilitate security and the safe transmission of important information in the digital domain, which generally requires a high embedding payload and good stego image quality. Recently, a steganographic framework known as wet paper coding has been utilized as an effective strategy in image hiding to achieve the requirements of high embedding payload, good quality and robust security. In this paper, besides employing this mechanism as a fundamental stage, we take advantage of two novel techniques, namely, an efficient n-indicator and a fuzzy edge detector. The first is to increase the robustness of the proposed system to guard against being detected or traced by the statistics methods while allowing the receiver without knowledge of secret data positions to retrieve the embedded information. The second is to improve the payload and enhance the quality of stego image. The experimental results show that our proposed scheme outperforms its ability to reduce the conflict among three steganography requirements. © 2009 Elsevier Inc. All rights reserved.


Xiaoping Z.,City College of New York | Baran S.,Natural science University | Cel W.,Lublin University of Technology | Cao Y.,Zhejiang Agriculture And forestry University
Ecological Chemistry and Engineering S | Year: 2015

The discussion about greenhouse gases emission mitigation focuses on the reduction of fossil fuels usage, which is extremely costly from the economic and social viewpoint. The analyses of CO2 and CH4 fluxes in the environment showed that intensifying natural photosynthesis and respiration process may significantly contribute to the mitigation of greenhouse gases emission. It has been proven that the intensity of photosynthesis in land ecosystems could compensate for the increase of CO2 emission from anthropological sources. © 2015 Xiaoping et al.


Lin C.-C.,Providence University | Chang C.-C.,Feng Chia University | Hoang Ngan Le T.,Natural Science University | Le H.B.,Natural Science University
2010 5th International Conference on Future Information Technology, FutureTech 2010 - Proceedings | Year: 2010

This study presents a novel scheme called a dual verifying (t, n) visual secret sharing scheme. In our proposed scheme, each participant receives a public key and an encrypted shadow instead of the original secret image through the public communication network. There are three goals achieved. The first is to generate a reconstructed secret image, which satisfies the general criteria high security, high quality image, low computational complexity, and no pixel expansion. This goal is achieved by high compression ratio, low complexity and good performance techniques in combination with Shamir's scheme. The second goal is to confirm shadow authentication by applying a digital signature scheme. The last goal is to verify the reliability of the reconstructed secret image by using an extracted halftone logo. The halftoning transform in this proposed scheme is executed with an error diffusion technique to guarantee image luminance and to enhance the quality of the reconstructed image. Moreover, a reversible data embedding technique is adopted to make sure each shadow not only carries authentication information but also maintains a small shadow size. © 2010 IEEE.

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