• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.747-769
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• 2020

This paper provides a semi-analytical approach to investigate the variations of 3D displacement components, electric potential, stresses, electric displacements and transverse vibration frequencies in laminated piezoelectric composite plates based on the scaled boundary finite element method (SBFEM) and the precise integration algorithm (PIA). The proposed approach can analyze the static and dynamic responses of multilayered piezoelectric plates with any number of laminae, various geometrical shapes, boundary conditions, thickness-to-length ratios and stacking sequences. Only a longitudinal surface of the plate is discretized into 2D elements, which helps to improve the computational efficiency. Comparing with plate theories and other numerical methods, only three displacement components and the electric potential are set as the basic unknown variables and can be represented analytically through the transverse direction. The whole derivation is built upon the three dimensional key equations of elasticity for the piezoelectric materials and no assumptions on the plate kinematics have been taken. By virtue of the equilibrium equations, the constitutive relations and the introduced set of scaled boundary coordinates, three-dimensional governing partial differential equations are converted into the second order ordinary differential matrix equation. Furthermore, aided by the introduced internal nodal force, a first order ordinary differential equation is obtained with its general solution in the form of a matrix exponent. To further improve the accuracy of the matrix exponent in the SBFEM, the PIA is employed to make sure any desired accuracy of the mechanical and electric variables. By virtue of the kinetic energy technique, the global mass matrix of the composite plates constituted by piezoelectric laminae is constructed for the first time based on the SBFEM. Finally, comparisons with the exact solutions and available results are made to confirm the accuracy and effectiveness of the developed methodology. What's more, the effect of boundary conditions, thickness-to-length ratios and stacking sequences of laminae on the distributions of natural frequencies, mechanical and electric fields in laminated piezoelectric composite plates is evaluated.

• Microbiology and Biotechnology Letters
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• v.17 no.1
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• pp.74-80
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• 1989

For improvement of photobiological hydrogen production, Rhodopseudomonas El5-1, a photo-synthetic becterium capable of producing n high yield of hydrogen, was immobilized and conditions for hydrogen production by immobilized cells were examined. The optimum concentration for the combined matrix was obtained when sodium alginate was used at final concentration of 4%. The immobilized cells may reduce the inhibitory effects of nitrogen or oxygen. To minimize the diffusion resistance of the nutrients in alginate gel, the bend size less than 2 mm in diameter was desirable. The immobilized cells were also able to utilize n wide range of organic substrates for the production of hydrogen. The hydrogen producing activity of the immobilized cells was maintained for 20 days without loss of activity during semi-continuous operation of the reactor by feeding of new medium periodically and continuous production of hydrogen could be successfully performed for 30 days.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 1993.06a
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• pp.4-5
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• 1993

Toxicity tests in our laboratory are conducted usually with mass-reared organisms. They are under the same environmentel conditions throughout seasons and are supplied at specific age. A total of 38 species of aquatic organisms are being reared. We have attempted to establish pruified strains or to select clones of various parthenogenic organisms. The merits or demerits of our culturing test organisms are discussed. The differences in the susceptibility among clones or strains of test organism are also discussed. For a single species test, algae, daphnia, fish are often used. However, we usually use early stages, but occasionally, adults fish are used for reproduction tests. As an another important aspect, the toxicity through food chains has been studied. In this study, we select a pair of species belonging different trophic levels. The differences between single species tests and multispecies tests will be discussed. Even a single species test intends to assess the effects of chemicals on ecosystem levels, however, this idea is not applicable to ecosystems. Single species tests with standard organisms and multispecies tests are contradictory in concept. One type of multispecles tests is indoor microcosms being composed of severel species artificially assembled, and another is composed of natural components (both indoor and outdoor). We have used three types of outdoor mesocosms using ponds and three types of artificial streams. The mesocosms is useful to not only to analyze the floral or faun61 changes but also to study the fate or behaviour of chemicals in naturd environments. Lastly, usefulness of the field observation or experiments or semi-field experiments will be discussed. This will enhance the exploitation of early warning systems utilizing indicator organisms or animal behaviour.aviour.

• Asian Journal of Turfgrass Science
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• v.10 no.2
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• pp.105-115
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• 1996

To find out the mineral cycles of calcium, magnesium and sodium in dynamic grassland cosystems in a steady state condition, this investigation was conducted along the northwest side on Mt. Kwanak. The experimental results may he suromarized on the communities of a Zoysia japonica and a Miscanthus sinesis as follows. As compared with some properties of the surface soils among two semi-natural grasslands, cal- cium (Ca) was greater quantity in a Zoysia japonica, whereas, in a Miscanthus sicensis, sodium (Na)and magnesium (Mg) were greater in Mt. Kwanak. For the case of steady production and release, the ratio of annual mineral production to the amount accumulated on the top of mineral soil in a steady state provides the estimates of release constant k. The release constants of Ca, Mg and Na of the litter were 0.42, 0.25 and 0.29 in the Zoysia japonica grassland, and were 0.41, 0.54 arid 0.62 in the Miscanthus sinensis grassland, respect- ively. The half times of Ca, Mg and Na required for the release or accumulation of the litter on the grassland were 1.65, 2.77 and 2.39 in the Zoysia japonica, and were 1.69, 1.28 and 1.12 in the Miscauthus sinensis, respectively. The increasing order of the turnover parameters of the elements was Ca, Na and Mg in the Zoysia japonica grassland, and was Na, Mg and Ca in the Miscanthus Si nens is grassland. The amounts of annual cycles for Ca, Mg, Na in the grassland ecosystem under the steady-state conditions were 1.29, 0.20 and 0.12 g /m$^2$ in the Zoysia japonica grassland and 3.91, 1.04 and 0.61 g /m$^2$ in the Miscanthus sinensis grassland.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.265-271
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• 2010

One of the most important aspect of esthetic dentistry is shade selection. Alterations to perception of color can occur as a result of numerous factors, including light source, tooth surface texture, observer's ability, surrounding colors, the angle of observation, light and dark adaptation and others. During the clinical procedures, tooth might be in dry or semi-dry condition. The purpose of this study was to compare the shade changes in wet and dry conditions of natural tooth. Groups of measurement are an initial wet condition as control, dry in 10seconds, 1 minute, 5minutes and 30seconds air dry. Using Shadeeye, color difference(${\Delta}E$) between measurements were analyzed and there were significant differences between groups. But most of the differneces were <3.7 ${\Delta}E$ unit. Such differences are below the threshold for perceivable color mismathces in intraoral condition. Shade selection with an intraoral colorimeter could be changes in dry and wet condition but there might be no significant differences in visual color mathing.

• Asian Journal of Turfgrass Science
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• v.11 no.1
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• pp.1-7
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• 1997

This study was performed to find out the mineral cycles of manganese and zinc in dynamic grassland ecosystems in a steady state condition at the northwest side on Mt. Kwanak. The experimental results may be summarized on the communities of a Zoysia japonica and a Miscanthus sincnsis as follows. As compared with some properties of the surface soils among two semi-natural grasslands, manganese and zinc was greater quantity in a Miscanthus sincnsis than in a Zoysia japonica on Mt. Kwana For the case of steady procluction and release, the ratio of annual mineral production to the amount accumulated on the top of mineral soil in a steady state provides the estimates of release constant k. The release constants of Mn and Zn of the litter were 0.19 and 0. 14 in the Zoysia japon- ica grassland, and were 0.44 and 0.41 in a Miscanthus sincnsis grassland, respectively. The halftimes of Mn and Zn required for the release or accumulation of the litter on the grassland were 3. 65 and 4.95 years in the Zoysia japonica, and were 1.57 and 1.69 years in the Miscanthus sincnsis, respectively. The amounts of annual cycles for Mn and Zn in the grassland ecosystem under the steady-state conditions were 58.60 and 21.46 mg /$m^2$ in a Zoysia japonica, and were 372.12 and 321.49 ing /m$^2$ in a Miscanthus sincnsis grassland. Key words: Zoysia japonica. Miscanthus sincnsis, Mt. Kwanak, Manganese, Zinc, Mineral cycles.

• The Plant Pathology Journal
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• v.36 no.2
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• pp.111-120
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• 2020

Powdery mildew of Indian mustard (Brassica juncea), caused by Erysiphe cruciferarum, is emerging as major problem in India. All the Indian mustard cultivars presently grown in India are highly susceptible to powdery mildew and so far no resistance source has been reported. In this study, with an aim to identify resistant source, 1,020 Indian mustard accessions were evaluated against E. cruciferarum PMN isolate, at Wellington, The Nilgiris, Tamil Nadu, India under natural hot spot conditions. The study identified one accession (RDV 29) with complete resistance against E. cruciferarum PMN isolate for the first time, which was consistent in five independent evaluations. Genetic analysis of F₁, F₂ and backcross populations obtained from the cross RSEJ 775 (highly susceptible) × RDV 29 (highly resistant) for two season revealed that the resistance is governed by two genes with semi-dominant and gene dosage effect. Further, a new disease rating system using six scales (0, 1, 2, 3, 4, and 5) has also been proposed in this study to score powdery mildew based on progress of fungal growth in different plant parts of the F₂ population. The outcome of this study viz. newly identified powdery mildew-resistant Indian mustard accession (RDV 29), information on inheritance of resistance and the newly developed disease rating scale will provide the base for development of powdery mildew-resistant cultivars of Indian mustard.

• Asian Journal of Turfgrass Science
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• v.9 no.4
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• pp.285-292
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• 1995

To elucidate the mineral cycles of potassium in a dynamic grassland ecosystem in a steady state condition, this investigation was cunducted along the northwest side on Mt. Kwanak. The exper-imental results may he summarized on communities of Z. japonica and M. sinensis as follows. As compared with some pronerties of the surface soils among two semi-natural grasslands, the levels of exchangeahle potassium were high in M. sinensis and low in Z. japonica. Contents of potassium for the litters of Z. japonica and M. sinensis were 1.69% and 2.51%, re-spectively. The annual production of potassium was 1.32 g /m$m^2$ in the Z. japonica grassland and 3. 08 g /m$m^2$in the M. sinensis grassland. For a case of steady production and release, the ratio of annual min- eral production to the amount accumulated on top of the mineral soil in a steady state provides estimates of the release constant k. The models of the release, accumulation and annual cycle of potassium in a grassland ecosystem are determined by the equation (1) to (3), respectively (Table 3). Since it requires a period of about each 0.693 /r, 3 /r and 5 /r years for the release and accumu-lation of 50, 95 and 99% of its steady-state level, the estimates for potassium in a dynamic grass-land ecosystem of Mt. Kwanak were 1.5, 6.6 and 11.0 years in the Z. japonica grassland, and were 2.7, 11.9 and 19.8 years in the M. sinensis grassland. The amounts of annual cycles for potassium in a grassland ecosystem under the steady-state conditions were 1.32 g /m$^2$ in the Z. japonica grassland and 3.08 g /$m^2$ in the M. sinensis grassland. Key words : ZQvsia japonica Ahscanthus sinensis, Mt. Kwanak, Potassium cycles.

• Steel and Composite Structures
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• v.38 no.5
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• pp.477-496
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• 2021

The main objective of this paper is to study vibration of sandwich open cylindrical panel with damaged core and FG face sheets based on three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution and boundary conditions. It is seen that for the large amount of power-law index "P", increasing this parameter does not have significant effect on the non-dimensional natural frequency parameters of the FG sandwich curved panel. Results indicate that by increasing the value of isotropic damage parameter "D" up to the unity (fully damaged core) the frequency would tend to become zero. One can dictate the fiber variation profile through the radial direction of the sandwich panel via the amount of "P", "b" and "c" parameters. It should be noticed that with increase of volume fraction of fibers, the frequency parameter of the panels does not increase necessarily, so by considering suitable amounts of power-law index "P" and the parameters "b" and "c", one can get dynamic characteristics similar or better than the isotropic limit case for laminated FG curved panels.

• Steel and Composite Structures
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• v.46 no.3
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• pp.367-383
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• 2023

In this investigation, an improved integral trigonometric shear deformation theory is employed to examine the vibrational behavior of the functionally graded (FG) sandwich plates resting on visco-Pasternak foundations. The studied structure is modelled with only four unknowns' variables displacements functions. The simplicity of the developed model being in the reduced number of variables which was made with the help of the use of the indeterminate integral in the formulation. The current kinematic takes into consideration the shear deformation effect and does not require any shear correction factors as used in the first shear deformation theory. The equations of motion are determined from Hamilton's principle with including the effect of the reaction of the visco-Pasternak's foundation. A Galerkin technique is proposed to solve the differentials governing equations, which enables one to obtain the semi-analytical solutions of natural frequencies for various clamped and simply supported FG sandwich plates resting on visco-Pasternak foundations. The validity of proposed model is checked with others solutions found in the literature. Parametric studies are performed to illustrate the impact of various parameters as plate dimension, layer thickness ratio, inhomogeneity index, damping coefficient, vibrational mode and elastic foundation on the vibrational behavior of the FG sandwich plates.