• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.695-706
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• 1996

In the control system $ \dot{x} = f(t,x(t)) + g(t,x(t))\dot{u}, x(0) = \bar{x}, t \in [0,T], $ this paper shows that the map from u with $L^1(m)$-topology to $x_u$ with $L^1(\mu)$-topology is Lipschitz continuous where f is $C^1$, $\mu$ is the Stieltjes measure derived from the function g which is not smooth in the variable t and $x_u$ is the solution of the above system corresponding to u under the assumption that $\dot{u}$ is bounded.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.99-104
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• 1998

본 논문은 효과적인 시계열 예측을 위한 새로운 퍼지 학습방법을 제안한다. 기존의 학습방법에서는 입력 데이터를 F(y(t),y(t-1),y(t-2)..)의 형태로 주어 예측을 수행했으나 본 논문에서 제안한 방법에서는 입력 데이터를 F(y(t)-y(t-1),y(t-1)-y(t-2)..)로 설정한다. 이것은 각 입력값의 차이를 새로운 입력으로 사용함으로써 유사한 시계열 분포를 좀더 능동적인 퍼지 규칙으로 만들기 때문에 Non-stationary한 데이터뿐만 아니라 기존의 시계열 데이터 예측방법 보다 나은 결과를 나타낸다. 알고리즘의 수행능력을 살펴보기 위해 Mackey-Glass time series와 Lorenz data를 사용하였다.

• Journal of Families and Better Life
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• v.4 no.2
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• pp.35-51
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• 1986

The purpose of this study is to establish family life cycle of farm and to analyze changes of economic conditions-income, consumption expenditures, savings, assets, and debts-in farm household according to the family life cycle. Income, consumption expenditures, savings, assets, and debts functions are also estimated by age of household head. The data of Farm Household Economy Survey which was conducted in 1983 by Ministry of Agriculture and Fisheries is used in this study. Among total data of 2000, 1603 are analyzed for mean, percentage, and regression using CRISP Program at Office of Rural Development. The results of study can be summarized as follows; 1) Eight stages of family life cycle of farm are established according to the growth of the first child. They are: Establishment stage, Child bearing and preschool stage, Elementary school stage, Middle and high school stage, College and vocational adjustment stage, Period of children's marriage, Re-adjustment stage, and isorganizing stage. 2) The economic conditions of farm household are significantly fluctuated by family life cycle. Among the eight stages, stage Ⅱ is considered relatively comfortable living period and stage Ⅲ, Ⅳ are the most difficult periods of farm household economy. 3) The estimated functions of income, consumption expenditures, savings, assets, and debts by age of household head are as follows; Y(income) = 2, 354, 832+98,456T-1,036T2(F=11.746) C(consumption expenditures) = 81,876+154,976T-1,552T2 (F=37.272) S(savings) = 2,272,956+56,511T+516T2(F=4.262) D(debts) = 903,929+28,300T-438T2(F=3.339) A(assets) = 200,816+1,213,336T-12,930T2(F=21.069) To carry on a reasonable farm household management, a suitable measure to cope with the desire of family and the economic conditions of farm household should be prepared.

• Archives of Metallurgy and Materials
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• v.64 no.2
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• pp.617-622
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• 2019

This study investigated the effect of T6 heat treatment on the microstructure and scratch wear behavior of hypoeutectic Al-12wt.%Si alloy manufactured by extrusion. Microstructural observation identified spherical eutectic Si phases before and after the heat treatment of alloys (F, T6). Phase analysis confirmed Al matrix and Si phase as well as Al₂Cu and Al₃Ni, Mg₂Si in both alloys. In particular, Al₂Cu was finer and more evenly distributed in T6 alloy. This resulted in Vickers hardness of T6 alloy that was 2.3 times greater compared to F alloy. The scratch wear test was conducted using constant load scratch test (CLST) mode and multi-pass scratch test (MPST) mode. The scratch coefficient and worn out volume obtained by such were used to evaluate wear properties before and after heat treatment. In the case of T6 alloy, its scratch coefficient was lower than F alloy in all load ranges. After 15 repeated tests to measure worn out volume, F alloy and T6 alloy measured 1.2×10^-1 mm³ and 7.8×10^-2 mm³, respectively. In other words, the wear resistance of T6 alloy were confirmed to be better than those of F alloy. In addition, this study attempted to identify the microstructural factors that contribute to the better scratch wear resistance of T6 alloy and wear mechanism from surface and cross-section observations after the wear tests.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.380-389
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• 2005

The Goldschmidt iterative algorithm for a floating point divide calculates it by performing a fixed number of multiplications. In this paper, a variable latency Goldschmidt's divide algorithm is proposed, that performs multiplications a variable number of times until the error becomes smaller than a given value. To calculate a floating point divide '$\frac{N}{F}$', multifly '$T=\frac{1}{F}+e_t$' to the denominator and the nominator, then it becomes ’$\frac{TN}{TF}=\frac{N_0}{F_0}$'. And the algorithm repeats the following operations: ’$R_i=(2-e_r-F_i),\;N_{i+1}=N_i{\ast}R_i,\;F_{i+1}=F_i{\ast}R_i$, i$\in${0,1,...n-1}'. The bits to the right of p fractional bits in intermediate multiplication results are truncated, and this truncation error is less than ‘$e_r=2^{-p}$'. The value of p is 29 for the single precision floating point, and 59 for the double precision floating point. Let ’$F_i=1+e_i$', there is $F_{i+1}=1-e_{i+1},\;e_{i+1}',\;where\;e_{i+1}, If '$[F_i-1]<2^{\frac{-p+3}{2}}$ is true, ’$e_{i+1}<16e_r$' is less than the smallest number which is representable by floating point number. So, ‘$N_{i+1}$ is approximate to ‘$\frac{N}{F}$'. Since the number of multiplications performed by the proposed algorithm is dependent on the input values, the average number of multiplications per an operation is derived from many reciprocal tables ($T=\frac{1}{F}+e_t$) with varying sizes. 1'he superiority of this algorithm is proved by comparing this average number with the fixed number of multiplications of the conventional algorithm. Since the proposed algorithm only performs the multiplications until the error gets smaller than a given value, it can be used to improve the performance of a divider. Also, it can be used to construct optimized approximate reciprocal tables. The results of this paper can be applied to many areas that utilize floating point numbers, such as digital signal processing, computer graphics, multimedia, scientific computing, etc

• Journal of the Korean Mathematical Society
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• v.57 no.1
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• pp.89-111
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• 2020

In the present paper, we give some characterization of the L₂ maximal estimate for the operator P^t_a,γf(Γ(x, t)) along curve with complex time, which is defined by $$P^t_{a,{\gamma}}f({\Gamma}(x,t))={\displaystyle\smashmargin{2}{\int\nolimits_{\mathbb{R}}}}\;e^{i{\Gamma}(x,t){\xi}}e^{it{\mid}{\xi}{\mid}^a}e^{-t^{\gamma}{\mid}{\xi}{\mid}^a}{\hat{f}}({\xi})d{\xi}$$, where t, γ > 0 and a ≥ 2, curve Γ is a function such that Γ : ℝ×[0, 1] → ℝ, and satisfies Hölder's condition of order σ and bilipschitz conditions. The authors extend the results of the Schrödinger type with complex time of Bailey [1] and Cho, Lee and Vargas [3] to Schrödinger operators along the curves.

• Journal of the Korean Society for information Management
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• v.6 no.1
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• pp.15-36
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• 1989

The r a p i d i n c r e a s e o f microcomputer technology has r e s u l t e d i n t h e broad a p p l i c a t i o n t o various f i e l d s . The purpose of t h l s paper 1s to design a computerized r e t r i e v a l system f o r nuclear information m a t e r i a l s using a microcomputer.

• Communications of the Korean Mathematical Society
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• v.16 no.4
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• pp.621-626
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• 2001

Let { $A_{>o}$ t= exp(M log t)} $_{t}$ be a dilation group where M is a real n$\times$n matrix whose eigenvalues has strictly positive real part, and let $\rho$be an $A_{t}$ -homogeneous distance function defined on ( $R^{n}$ ). Suppose that K is a function defined on ( $R^{n}$ ) such that /K(x)/$\leq$ (No Abstract.see full/text) for a decreasing function defined on (t) on R+ satisfying where wo(x)=│log│log (x)ll. For f$\in$ $L_{1}$ ( $R^{n}$ ), define f(x)=sup t>0 Kt*f(x)=t-v K(Al/tx) and v is the trace of M. Then we show that \ulcorner is a bounded operator of $L_{-{1}( $R^{n}$ ) into $L^1$,$\infty$( $R^{n}$).

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.4
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• pp.253-263
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• 2020

Purpose : The purpose of this study was conducted to compare the fear of falling, self-efficacy and fall prevention behavior according to the fall experience of the elderly. Methods : The subjects of this study were 162 elderly in B metropolitan city. The data collection period was from September 10th to November 30th of 2018. The collected data was processed using SPSS 21.0 and was analyzed using descriptive statistics, t-test, ANOVA, Scheffe's test. Results : The mean scores for fear of falling according to the fall experience and no fall experience of the elderly were 2.28±0.63 and 1.84±0.64 respectively and the results showed that fear of falling (t=4.26, p<.001) and self-efficacy of falling (t=3.88, p<.001) were significantly different between the two groups, but the mean scores for fall prevention behavior according to the fall experience and no fall experience of the elderly were 1.63±0.20 and 1.67±0.17 respectively and there was no significantly different in fall prevention behavior (t=-1.16, p=.25). Fear of falling according to the fall experience was significantly different by age (F=3.25, p<.05) and physical activity related to daily life (F=13.22, p<.001). Self-efficacy according to the fall experience was significantly different by age (F=3.03, p<.05), income per month (F=3.74, p<.05) and physical activity related to daily life (F=11.99, p<.001). But fall prevention behavior was no significantly different of general characteristics. Fear of falling according to the no fall experience was significantly different by age (F=3.37, p<.05), marriage status (F=3.37, p<.05), education level (F=5.15, p<.01), income per month (F=3.58, p<.05) and physical activity related to daily life (F=15.71, p<.001). Self-efficacy according to the no fall experience was significantly different by sex (t=2.32, p<.05), age (F=5.20, p<.01), marriage status (F=5.04, p<.01), education level (F=6.55, p<.001), income per month (F=5.99, p<.001) and physical activity related to daily life (F=18.86, p<.001). Fall prevention behavior was significantly different by marriage status (F=3.51, p<.05). Conclusion : The results of this study suggest the following : it is necessary to develop a program that can lower the fear of falling in the elderly and to increase the self-efficacy of falling, and to develop an education program that can improve the elderly's practice of fall prevention behavior regardless of the fall experience and to verify its effectiveness.

• Journal of Korean Society for Geospatial Information Science
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• v.14 no.1 s.35
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• pp.57-63
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• 2006

The purpose of this study is to correct data on 3 intersection ranging from Kwangchun INT. to Nongsung INT. by the means of VTR recording and site survey and to measure the responsiveness of performance index by diversifying the platoon dispersion factor in signal progression simulation. The results are as follows : 1. The value of platoon dispersion factor was 0.28-0.33. The value in up stream is lower than that of in down stream even on the same intersection. 2. The platoon index showed big changes, though performance index didn't according to platoon dispersion factor. Therefore the value of platoon dispersion factor which is inner variable in T7F can be fixed for 0.34. 3. There was only little divergence in performance index changes according to platoon dispersion factor in designing the progression or T7F model.