• Communications of Mathematical Education
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• v.33 no.2
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• pp.105-122
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• 2019

In Korean textbooks, by T(x,y) = (x+a, y+b) where a and b are horizontal and vertical changes respectively, an arbitrary point on the original figure f(x, y) = 0 has been expressed as a point (x, y) and a point on a translated figure f(x-a, y-b) = 0 has been expressed as a point (x', y'). If an arbitrary point on a figure f(x, y) = 0 is expressed as a point (x, y), then a point (x, y) and a figure f(x, y) = 0 are different targets but the same characters are used. In this following study, there were found that the expressions in these textbooks were stuck for more than 50 years, so students' thoughts were stiff. And therefore these are a need to be improved so that those things are studied as follows. First, inducing a formula, what are the students' responses like when were expressed differently from textbooks? Second, based on the results reviewed, how will the expressions of the textbook be revised? Third, how do the students respond to the modified expressions? As the result, a point on the original figure were expressed differently from textbooks and a point on a translated figure was put as a point (x, y), and about it, all of the students surveyed said that this improved expressions made in the study were easier.

• Bulletin of the Korean Mathematical Society
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• v.21 no.1
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• pp.1-5
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• 1984

The notion of linear 2-normed spaces was introduced by S. Gahler ([8,9,10,11]), and these space have been extensively studied by C. Diminnie, R. Ehret, S. Gahler, K. Iseki, A. White, Jr, and others. For nonzero vectors x,y in X, let V(x,y) denote the subspace of X generated by x and y. A linear 2-normed space (X,v) is said to be strictly convex ([3]) if v(x+y,z)=v(x,z)+v(y+z) and z not.mem.V(x,y) imply that y=ax for some a>0. Some characterizations of strict convexity for linear 2-normed spaces are given in [1,3,4,5,12]. Also, a linear 2-normed space (X,v) is said to be strictly 2-convex ([6]) if v(x,y)=v(x,z)=v(y,z)=1/3v(x+z, y+z)=1 implies that z=x+y. These space have been studied in [2,4,6,13]. It is easy to see that every strictly convex linear 2-normed space is always strictly 2-convex but the converse is not necessarily true. Throughout this paper, let (X,v) denote a linear 2-normed space.

• Kyungpook Mathematical Journal
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• v.57 no.4
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• pp.667-676
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• 2017

We study the positive $C^1$ function z = f(x, y) defined on the plane ${\mathbb{R}}^2$. For a rectangular domain $[a,b]{\times}[c,d]{\subset}{\mathbb{R}}^2$, we consider the volume V and the surface area S of the graph of z = f(x, y) over the domain. We also denote by (${\bar{x}}_V,\;{\bar{y}}_V,\;{\bar{z}}_V$) and (${\bar{x}}_S,\;{\bar{y}}_S,\;{\bar{z}}_S$) the geometric centroid of the volume under the graph of z = f(x, y) and the centroid of the graph itself defined on the rectangular domain, respectively. In this paper, first we show that among nonconstant $C^2$ functions with isolated singularities, S = kV, $k{\in}{\mathbb{R}}$ characterizes the family of catenary rotation surfaces f(x, y) = k cosh(r/k), $r={\mid}(x,y){\mid}$. Next, we show that one of $({\bar{x}}_S,\;{\bar{y}}_S)=({\bar{x}}_V,\;{\bar{y}}_V)$, $({\bar{x}}_S,\;{\bar{z}}_S)=({\bar{x}}_V,\;2{\bar{z}}_V)$ and $({\bar{y}}_S,\;{\bar{z}}_S)=({\bar{y}}_V,\;2{\bar{z}}_V)$ characterizes the family of catenary rotation surfaces among nonconstant $C^2$ functions with isolated singularities.

• Microbiology and Biotechnology Letters
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• v.24 no.4
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• pp.408-414
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• 1996

The SecY is a central component of the protein export machinery that mediate the translocation of secretory proteins across the plasma membrane, and has been known to be rate-limiting factor of secretion in Escherichia coli. In order to study the extracellular protein secretion in Gram-positive microorganism, we have, constructed strains harboring more than one copy of the gene for SecY. Firstly, the gene, for B. subtilis SecY and its promoter region was subcloned into pDH32 and the chimeric vector was inserted into amyE locus by homologous recombination. Secondly, low copy number vector, pCED6, was also used for subcloning the secY gene and for constructing a strain which harbors several copies of secY. The KH1 cell which harbor two copies of secY on the chromosome excreted more extracellular proteins than the wild type PB2. Moreover, the KH2 cells which harbor several copies of secY in pCED6 vector excreted more extracellular proteins than the KH1 cells. Here, we found that the capacity of protein secretion is partly controlled by the number of secY and it is suggested that SecY has also an important role in protein secretion in B. subtilis, a gram positive microorganism, as like in E. coli. This will promote the use of B. subtilis as a host for the expression of useful foreign gene and excretion of precious proteins.

• Progress in Superconductivity
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• v.11 no.1
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• pp.42-46
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• 2009

With an aim of comparison, single grain Y-Ba-Cu-O (YBCO) bulk superconductors were fabricated using a liquid infiltration growth (LIG) process and a conventional melt growth (MTG) process with top seeding. The MTG process uses an $YBa_2Cu_3O_{7-x}$(Y123) powder as a precursor, while the LIG process uses $Y_2BaCuO_5(Y211)/Ba_3Cu_5O_8(Y035)$ pre-forms. The growth of a single Y123 domain on the top seed was successful in the both processes. Different feature between the two processes is the interior microstructure regarding the critical current density ($J_c$). The LIG-processed YBCO sample showed a lower porosity, more uniform distribution of Y211 particles and the enhanced Y211 refinement compared to the conventional MTG process. The $J_c$ improvement in the LIG process is attributed to the dispersion of finer Y211 particles as well as lower porosity within the Y123 superconducting matrix.

• Bulletin of the Korean Mathematical Society
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• v.45 no.4
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• pp.663-670
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• 2008

In this paper, the aim is to solve the neutral delay differential equations in the following form using multiquadric approximation scheme, (1) $$\{_{\;y(t)\;=\;{\phi}(t),\;\;\;\;\;t\;{\leq}\;{t_1},}^{\;y'(t)\;=\;f(t,\;y(t),\;y(t\;-\;{\tau}(t,\;y(t))),\;y'(t\;-\;{\sigma}(t,\;y(t)))),\;{t_1}\;{\leq}\;t\;{\leq}\;{t_f},}$$ where f : $[t_1,\;t_f]\;{\times}\;R\;{\times}\;R\;{\times}\;R\;{\rightarrow}\;R$ is a smooth function, $\tau(t,\;y(t))$ and $\sigma(t,\;y(t))$ are continuous functions on $[t_1,\;t_f]{\times}R$ such that t-$\tau(t,\;y(t))$ < $t_f$ and t - $\sigma(t,\;y(t))$ < $t_f$. Also $\phi(t)$ represents the initial function or the initial data. Hence, we present the advantage of using the multiquadric approximation scheme. In the sequel, presented numerical solutions of some experiments, illustrate the high accuracy and the efficiency of the proposed method even where the data points are scattered.

• Journal of Environmental Science International
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• v.7 no.5
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• pp.599-605
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• 1998

The purpose of this work was to examine whether X-Y chromosome dissociation in the primary spermatocytes of mice could be used as an in vivo short-term assaying system that detect environmental mutagens. Four alkylating agents(EMS, MMS, MMC and MNNG) which were known as strong mutagens were administered to BALB/c male mice 3-4 months old. In the control group, the mean frequencies of previously dissociated X and Y chromosomes and autosomes were 7.17% and 2.12%, respectively. Compared to the control group, mutagen-treated groups have no significant differences in dissociation rate of autosomes, while these poops were about 1.2-2.5 times higher in the frequencies of X-Y dissociation. Generally, X-Y dissociation frequency increased consistently with the concentration of mutagens whereas the tendency of autosome dissociation frequency was variable among several mutagens. These results suggest that X-Y dissociation in the primary spermatocytes of mice is applicable as an vivo short-term assaying system for environmental mutagens. There were significantly distinct increase in dissociation of X-Y chromosome in both the hybrid and parents but the X-Y previous dissociation of hybrid appeared higher frequency than BALB /c and wild mice. These results indicate that the factor related to binding X-Y chromosome is specific to strains.

• Journal of the Korean Ceramic Society
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• v.37 no.9
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• pp.839-846
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• 2000

통전활성 소결법을 이용하여 단상의 세라믹스(PSZ) 및 금속(NiCrAlY)과 PSZ/NiCrAlY 복합체를 각 소결온도에서 제조하였으며, 이에 대한 특성평가는 개량형 소형펀치 시험법을 이용하여 수행하였다. 복합체의 밀도 및 경도에 미치는 소결온도의 영향은 NiCrAlY의 부피분율 증가에 따라 감소되었으며, 중간조성에서의 밀도 및 경도는 연속적인 변화를 나타내었다. 파괴인성의 변화에서는 60vol%-NiCrAlY 이상의 조성에서 급격한 증가를 나타내었으며, 짧은 소결시간 및 빠른 승온속도 등 통전활성 소결법의 장점에 의해 단상의 PSZ에서도 10 MPa.m$^{1}$2/ 의 높은 파괴인성 값을 얻을 수 있었다. PSZ/NiCrAlY 복합체에서의 특성은 소결온도와 NiCrAlY의 부피분율에 의해 지배적으로 영향을 받았으며, 단상의 PSZ은 전형적인 취성거동을 나타내었고 80vol%-NiCrAlY 까지의 복합체에서는 부분적인 취성 및 소성거동을 함께 나타내었다. 각 소결체에서 최고의 특성을 나타내고 소결온도는 단상의 PSZ 경우인 140$0^{\circ}C$에서부터 단상의 NiCrAlY 경우인 120$0^{\circ}C$까지 최대 20$0^{\circ}C$의 차이를 나타내었으며, PSZ과 NiCrAlY의 조성비에 따라서 연속적인 변화를 보였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.4
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• pp.267-273
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• 1998

The band structures of $Si_{1-x}Ge_x$ layers grown on $Si_{1-y}Ge_y$ substrate are calculated using k$\cdot$p and strain Hamiltonians. The hole drift mobilities in the plane direction are then calculated by taking into account the screening effect and the density-of-states of the impurity band. When $Si_{1-x}Ge_x$ is grown on Si substrate, the mobilities of (110) and (111) $Si_{1-x}Ge_x$ layers are larger than that of (001) $Si_{1-x}Ge_x$. However, due to the large defect and surface scattering, (110) and (111) $Si_{1-x}Ge_x$ layers may not be useful for the development of the fast device. Meanwhile, when Si is grown on $Si_{1-y}Ge_y$ substrate, the mobilities of (001) and (110) Si layers are greatly enhanced. Based on the amount of defect and the surface scattering, it is expected that Si grown on (001) $Si_{1-y}Ge_y$ substrate, where the Ge contents is larger than 10%(y>0.1), has the highest mobility.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.125-132
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• 2018

We studied a simple approach for synthesis of mesoporous Y(M-Y) from commercial zeolite Y precursors by treating of NaOH with $CH_3(CH_2)_{15}N(Br)(CH_3)_3$ as template. The physicochemical properties of the mesoporous zeolites Y were then analyzed using XRD, nitrogen full-isotherms at 77 K, SEM and TEM. The nitrogen adsorption-desorption analysis showed that surface area and pore diameter of synthesized mesoporous zeolite Y(M-Y) were $1072m^2/g$ and ~3.3 nm, respectively. And M-Y was applied for the removal of $Mn^{2+}$ and $Fe^{2+}$ from aqueous solution. This material, which introduces mesoporosity with zeolite Y character, displayed a superior adsorption capacity than commercial zeolite Y when used as an adsorbent for the removal of $Mn^{2+}$ and $Fe^{2+}$.