• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6C
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• pp.648-658
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• 2003

As the usage of image/video contents increase, a security problem for the payed image data or the ones requiring confidentiality is raised. This paper proposed an image encryption methodology to hide the image information. The target data of it is the result from quantization in wavelet domain. This method encrypts only part of the image data rather than the whole data of the original image, in which three types of data selection methodologies were involved. First, by using the fact that the wavelet transform decomposes the original image into frequency sub-bands, only some of the frequency sub-bands were included in encryption to make the resulting image unrecognizable. In the data to represent each pixel, only MSBs were taken for encryption. Finally, pixels to be encrypted in a specific sub-band were selected randomly by using LFSR(Linear Feedback Shift Register). Part of the key for encryption was used for the seed value of LFSR and in selecting the parallel output bits of the LFSR for random selection so that the strength of encryption algorithm increased. The experiments have been performed with the proposed methods implemented in software for about 500 images, from which the result showed that only about 1/1000 amount of data to the original image can obtain the encryption effect not to recognize the original image. Consequently, we are sure that the proposed are efficient image encryption methods to acquire the high encryption effect with small amount of encryption. Also, in this paper, several encryption scheme according to the selection of the sub-bands and the number of bits from LFSR outputs for pixel selection have been proposed, and it has been shown that there exits a relation of trade-off between the execution time and the effect of the encryption. It means that the proposed methods can be selectively used according to the application areas. Also, because the proposed methods are performed in the application layer, they are expected to be a good solution for the end-to-end security problem, which is appearing as one of the important problems in the networks with both wired and wireless sections.

• Korean Journal of Environment and Ecology
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• v.23 no.5
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• pp.431-438
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• 2009

The main purpose of this research is to prepare and provide basic materials for the propagational strategy of eelgrass by investigating on the morphological adaptation of Korean Zostera marina to ocean currents. An eelgrass plant mainly consists of rhizome, leaf sheath, leaves and roots. The rhizome is the horizontal stem of the plant that serves as the backbone from which the leaves and roots emerge. The leaf sheath is the bundle at the base of the leaves that holds the leaves together, protecting the meristem, the primary growth point of the shoot. Leaves originate from a meristem which is protected by a sheath at the actively growing end of the rhizome. As the shoot grows, the rhizome elongates, moving across or within the sediment, forming roots as it progresses. The aggregated leaves from the leaf sheath are found to have two cell layers on one side and multiple layers of airy tissues called aerenchyma on the other. The aerenchyma tissues are developed in multi-layered cell structures surrounding the veins which are formed in the leaf sheath. Generative shoots are made of rhizomes, which are circular or ovoidal, stem, and spathe and spadix. The transverse section of rhizome and the stem and central floral axis is found to be circular, ovoid and in the shape of convex respectively, and the vascular bundle, which is a part of transport system, has one large tube in the center and two small tubes on both sides. The layers of collenchyma cells numbered from 12 to 15 in the stem, and from 7 to 12 in the rhizome. The seed coat is composed of sclereids, small bundles of sclerenchyma tissues, which prevent the influx of sea water from the outside and help endure the environmental stress. In conclusion, alternative multi-layer structure in circular, convex type aggregated leaf base are interpreted to morphological adaption as doing tolerable elastic structure through movement of seawater. The generative shoots develop long slim stem and branches in circular or ovoidal shapes to minimize the adverse impacts of sea current, which can be interpreted as the plant's morphological adaptation to its environment.

• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.293-299
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• 2010

Vertically aligned ZnO nanorods on Si (111) substrate were prepared by hydrothermal method. The ZnO nanorods on spin-coated seed layer were synthesized at $140^{\circ}C$ for 6 hours in autoclave and were thermally annealed in argon atmosphere for 20 minutes at temperature of 300, 500, $700^{\circ}C$. The effects of the thermal annealing on the structural and optical properties of the grown on ZnO nanorods were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), photoluminescence (PL). All the ZnO nanorods show a strong ZnO (002) and weak (004) diffraction peak, indicating c-axis preferred orientation. The residual stress of the ZnO nanorods is changed from compressive to tensile by increasing annealing temperature. The hexagonal shaped ZnO nanorods are observed. The PL spectra of the ZnO nanorods show a sharp near-band-edge emission (NBE) at 3.2 eV, which is generated by the free-exciton recombination and a broad deep-level emission (DLE) at about 2.12~1.96 eV, which is caused by the defects in the ZnO nanorods. The intensity of the NBE peak is decreased and the DLE peak is red-shifted due to oxygen-related defects by thermal annealing.

• Korean Journal of Environment and Ecology
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• v.35 no.6
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• pp.579-593
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• 2021

In order to understand the types of vegetation in warm temperate-climate zones, vegetation was investigated in several island areas in Jeollanam-do (Jindo, Wando, Gangjin, Goheung, and Yeosu). The evaluation standard for degraded level of warm temperate forests were proposed based on the importance percentage (IP) in canopy layer of the evergreen broad-leaf forests and the number of arboreal evergreen broad-leaf species. Through these measurements, the restoration types and techniques for each degraded level were estimated, and it is intended to be used in establishing restoration plans for the southwest coast island area. The vegetation was analyzed using the two-way indicator species analysis (TWINSPAN) method using survey data of 307 plots. As a result, it was divided into 8 communities, and the appearance characteristics of evergreen broad-leaf species were identified in each community. Community I was located on the lower slope at an altitude of 86.6 m, and Neolitsea sericea and Castanopsis sieboldii were dominant. Communities II and III were the vegetation types that appear on the coast below an altitude of 10.5 to 22.5 m, and Machilus thunbergii, Cinnamomum japonicum, N. sericea, and C. sieboldii were dominant. Communities IV and V were vegetation types that appeared in the lower and middle slops between the altitudes of 71.9 to 153.4m, and C. sieboldii was dominant. In community VI, the N. sericea was dominant in the lower and middle slops at an altitude of 166.9 m. The last communities VII and VIII were the vegetation types that appeared on the middle slop at an altitude of 187.8 to 246.2 m. Also, Quercus acuta and Q. salicina were present. In summary, the evergreen broad-leaf forests dominated by M. thunbergii, C. japonicum, and N. sericea appeared mainly in the coastal areas of the lowlands. The community of C. sieboldii was distributed higher inland than this community. The communities that appeared mainly in the inland highlands at levels above these two communities were Q. acuta and Q. salicina. The degraded level was classified as 0 to V, according to the IP of arboreal evergreen broad-leaf species and the number of arboreal evergreen broad-leaf species. According to the degraded level, the restoration types (preservation, induction, improvement, creation) and the restoration techniques were determined.