• Journal of Power Electronics
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• v.9 no.2
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• pp.275-287
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• 2009

This paper investigates analytical models of Conduction and Switching Losses (CASLs) of a matrix-Z-source converter (MZC). Two analytical models of the CASLs are obtained through the examination of operating principles for a Z-source inverter and ac-dc matrix converter respectively. Based on the two models, the analytical model of CASLs for a MZC is constructed and visualized over a range of exemplified operating- points, each of which is defined by the combination of power factor (pt) and modulation index (M). The model provides a measurable way to approximate the total losses of the MZC.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.10-12
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• 2008

Silicon micro-patterns were fabricated on Si (100) wafers using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and micro-channels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces were then evaluated for their micro-friction behavior in comparison with those of bare Si (100) flat, Z-DOL coated Si (100) flat and uncoated Si patterns. Experimental results showed that the chemically treated (Z-DOL coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the test materials. The results indicate that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro/Nano-Electro-Mechanical-Systems (MEMS/NEMS).

• Journal of Welding and Joining
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• v.23 no.2
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• pp.59-65
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• 2005

A leaky surface acoustic wave (LSAW) velocity was measured using a scanning acoustic microscope on the ceramic/metal interface in order to investigate material properties. The inverse Fourier transform (IFFT) of the V(z) curve contains the reflectance function of a liquid-specimen interface. So, the longitudinal, transverse, and Rayleigh wave velocities for each layer are obtained by the inversion of the V(z) curve at the same time. This paper contains mainly the experimental procedure for measurements of the LSAW velocity, and the results obtained for the velocity variation of individual layer after the thermal shock. It is shown that this method is useful in measuring the material properties under external stress.

• Asian Journal of Turfgrass Science
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• v.8 no.1
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• pp.37-46
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• 1994

We study on the standing crop and edaphic factor of grasslands in Chulwon near the D.M.Z. The widespread and most abundant grasses are Arundinella hirta and Miscanthus sinensis in the upland fields of D.M.Z. The vascular flora of grasslands in Umi-dong and Sukda-dong near the D.M.Z. and composed of total 25 species, the most important of which ace Arundinella hirta and Miscanthus sinensis These two species contribute greatly to the standing crop of live naterial was in excess of $107.6g /m^2$. Correlation between standing ccop and water content, organic matter, total nitrogen, or avail-able phosphorus of grassland soils in area studied is high significant. It is argued that these edaphic factors affect the growth of grasses in Umi-dong and Sukda-dong grasslands.

• Communications of the Korean Mathematical Society
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• v.34 no.4
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• pp.1049-1067
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• 2019

In this paper, we discuss the number of distinct fuzzy subgroups of the group ${\mathbb{Z}}_{p^n}{\times}{\mathbb{Z}}_{q^m}{\times}{\mathbb{Z}}_r$, m = 1, 2, 3 where p, q, r are distinct primes for any $n{\in}{\mathbb{Z}}^+$ using the criss-cut method that was proposed by Murali and Makamba in their study of distinct fuzzy subgroups. The criss-cut method first establishes all the maximal chains of the subgroups of a group G and then counts the distinct fuzzy subgroups contributed by each chain. In this paper, all the formulae for calculating the number of these distinct fuzzy subgroups are given in polynomial form.

• Asian Journal of Turfgrass Science
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• v.11 no.4
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• pp.289-294
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• 1997

The cycles of heavy metals, mercury, lead and cadmium, were investigated on in dynamic grassland ecosystems at a steady state in Zoysia japonica and Miscanthus sinensis in Mt. Kwanak, Korea. Estimates of decay constants of heavy metals based on experimental and methomatical model, were Hg 0.14, Pb 0.17 and Cd 0.41 of Z. japonica grassland, and Hg 0.33, Pb 0.13 and Cd 0.56 of M sinensis grassland. The durations of reaching half of initial amounts in Z. japonica and M. sinensis grassland, were Hg 4.95, Pb 4.07 and Cd 1.69 years, and Hg 2.10, Pb 5.33 and Cd 1.24 years respectively. Times needed for 99% decomposed were longer in Z. japonica than M. sinensis grassland. Decay velocity of constituents of surface soil layers were more rapidly in M. sinensis than Z. japonica grassland. Key words: Cycles of heavy metals, Mercury, Lead, Cadmium, Zoysia japonica. Miscanthus sineusis, Mt. Kwanak, Decay constants.

• Honam Mathematical Journal
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• v.41 no.1
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• pp.197-206
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• 2019

We consider the extended generalized Hecke groups ${\bar{H}}_{3,q}$ generated by $X(z)=-(z-1)^{-1}$, $Y(z)=-(z+{\lambda}_q)^{-1}$ with ${\lambda}_q=2\;cos({\frac{\pi}{q}})$ where $q{\geq}3$ an integer. In this work, we study the generalized Pell sequences in ${\bar{H}}_{3,q}$. Also, we show that the entries of the matrix representation of each element in the extended generalized Hecke Group ${\bar{H}}_{3,3}$ can be written by using Pell, Pell-Lucas and modified-Pell numbers.

• Communications of the Korean Mathematical Society
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• v.38 no.3
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• pp.733-740
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• 2023

Let R be a commutative ring and M be an R-module. The dimension graph of M, denoted by DG(M), is a simple undirected graph whose vertex set is Z(M) ⧵ Ann(M) and two distinct vertices x and y are adjacent if and only if dim M/(x, y)M = min{dim M/xM, dim M/yM}. It is shown that DG(M) is a disconnected graph if and only if (i) Ass(M) = {𝖕, 𝖖}, Z(M) = 𝖕 ∪ 𝖖 and Ann(M) = 𝖕 ∩ 𝖖. (ii) dim M = dim R/𝖕 = dim R/𝖖. (iii) dim M/xM = dim M for all x ∈ Z(M) ⧵ Ann(M). Furthermore, it is shown that diam(DG(M)) ≤ 2 and gr(DG(M)) = 3, whenever M is Noetherian with |Z(M) ⧵ Ann(M)| ≥ 3 and DG(M) is a connected graph.

• The Pure and Applied Mathematics
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• v.31 no.1
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• pp.49-56
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• 2024

For a Polynomial P(z) = Σⁿ_j=0 a_jz^j with a_j ≥ a_j-1, a₀ > 0 (j = 1, 2, ..., n), a classical result of Enestrom-Kakeya says that all the zeros of P(z) lie in |z| ≤ 1. This result was generalized by A. Joyal et al. [3] where they relaxed the non-negative condition on the coefficents. This result was further generalized by Dewan and Bidkham [9] by relaxing the monotonicity of the coefficients. In this paper, we use some techniques to obtain some more generalizations of the results [3], [8], [9].

• Childhood Kidney Diseases
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• v.4 no.1
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• pp.84-91
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• 2000

Purpose: To improve the recovery of growth deficit after renal transplantation in children, we analysed the factors affecting height growth after renal transplantation. Methods: We reviewed medical records of fifty-six children in whom height data were available for three years after transplantation. All height data were converted into Z-scores. We analyzed the effects of sex, age at transplantation, cumulative mean steroid dose for 3 years, serum creatinine levels, height at transplantation, donor source and history of prior dialysis on patients' z-scores and delta Zs. Results: The Z-scores at transplantation were lower in patients of younger age (P=0.007). When baseline Z-scores were lower, the delta Zs were higher (P<0.01), but the Z-scores after transplantation were still lower (P<0.001). According to the analysis of the partial correlation coefficients, Z-scores and delta Zs at 1 year after transplantation were higher in groups of younger age and of lower steroid dosages (P<0.05). The delta Zs at 6 month and 1 year after transplantation were lower in the group with abnormally higher serum creatinine (P<0.05). There was no difference in Z-scores between groups of different genders, donor sources, and histories of previous dialysis. Conclusion: The children of younger age, on lower steroid dosage, with less growth retardation at transplantation, and with normal graft function had better height growth recoveries after renal transplantation.