• 소성∙가공
• /
• 제27권6호
• /
• pp.347-355
• /
• 2018

This study investigated the effects of the processing number of multi-axial diagonal forging (MADF) on the microstructural changes of OFC fabricated by MADF processes. The as-extruded OFC was cut to $25mm^3$ cube for the MADF processes. The MADF process consists of plane forging with a thickness reduction of 30% and diagonal forging with a diagonal forging angle of $135^{\circ}$. In order to analyze the microstructural evolutions according to the number of repetitions, 1, 2, 3 and 4 cycles of the MADF process were performed. OFC specimens were successfully deformed without surface cracking for up to 4 cycles of MADF. The grain size, average misorientation and average grain orientation spread (GOS) of MADF processed materials were analyzed using EBSD technique and their Vicker's hardness were also measured. The results showed that MADF process effectively refined the microstructure of OFC with initial average grain size of $84.2{\mu}m$. The average grain sizes of specimens MADF processed for 1, 2, 3, 4 cycles were refined to be $8.5{\mu}m$, $2.2{\mu}m$, $1.5{\mu}m$, $1.1{\mu}m$, respectively. The grain refinement seemed to be saturated when OFC was MADF processed over 2 cycles. In the case of specimens subjected to two or more cycles of MADF, the degree of decrease in average grain size was drastically reduced as the number of cycles increased due to softening phenomena such as dynamic recovery or dynamic recrystallization during processing. The degree of increase in average Vicker's hardness was also dramatically reduced as the number of cycles increased due to the same reason.

• East Asian mathematical journal
• /
• 제35권1호
• /
• pp.67-75
• /
• 2019

We investigate the averaging value of a random sampling of a Dirichlet series with some condition using Poisson distribution. Our result is the following: Let $L(s)={\sum}^{\infty}_{n=1}{\frac{a_n}{n^s}}$ be a Dirichlet series that converges absolutely for Re(s) > 1. If $X_t$ is an increasing random sampling with Poisson distribution and there exists a number $0<{\alpha}<{\frac{1}{2}}$ such that ${\sum}_{n{\leq}u}a_n{\ll}u^{\alpha}$, then we have $${\mathbb{E}}L(1/2+iX_t)=O(t^{\alpha}{\sqrt{{\log}t}})$$, for all sufficiently large t in ${\mathbb{R}}$. As a result, we get the behaviour of $L({\frac{1}{2}}+it)$ such that L is a Dirichlet L-function or a modular L-function, when t is sampled by the Poisson distribution.

• 자원환경지질
• /
• 제4권4호
• /
• pp.225-234
• /
• 1971

With the advance of civilization and steadily increasing population rivalry and competition for the use of the sewage, culverts, farm irrigation and control of various types of flood discharge have developed and will be come more and more keen in the future. The author has tried to calculated a formula that could adjust these conflicts and bring about proper solutions for many problems arising in connection with these conditions. The purpose of this study is to find out effective sewage, culvert, drainage, farm irrigation, flood discharge and other engineering needs in the Taegu area. If demands expand further a new formula will have to be calculated. For the above the author estimated methods of control for the probable expected rainfall using a formula based on data collected over a long period of time. The formula is determined on the basis of the maximum daily rainfall data from 1921 to 1971 in the Taegu area. 1. Iwai methods shows a highly significant correlation among the variations of Hazen, Thomas, Gumbel methods and logarithmic normal distribution. 2. This study obtained the following major formula: ${\log}(x-2.6)=0.241{\xi}+1.92049{\cdots}{\cdots}$(I.M) by using the relation $F(x)=\frac{1}{\sqrt{\pi}}{\int}_{-{\infty}}^{\xi}e^{-{\xi}^2}d{\xi}$. ${\xi}=a{\log}_{10}\(\frac{x+b}{x_0+b}\)$ ($-b<x<{\infty}$) ${\log}(x_0+b)=2.0448$ $\frac{1}{a}=\sqrt{\frac{2N}{N-1}}S_x=0.1954$. $b=\frac{1}{m}\sum\limits_{i=1}^{m}b_s=-2.6$ $S_x=\sqrt{\frac{1}{N}\sum\limits^N_{i=1}\{{\log}(x_i+b)\}^2-\{{\log}(x_0+b)\}^2}=0.169$ This formule may be advantageously applicable to the estimation of flood discharge, sewage, culverts and drainage in the Taegu area. Notation for general terms has been denoted by the following. Other notations for general terms was used as needed. $W_{(x)}$ : probability of occurranec, $W_{(x)}=\int_{x}^{\infty}f_{(n)}dx$ $S_{(x)}$ : probability of noneoccurrance. $S_{(x)}=\int_{-\infty}^{x}f_(x)dx=1-W_{(x)}$ T : Return period $T=\frac{1}{nW_{(x)}}$ or $T=\frac{1}{nS_{(x)}}$ $W_n$ : Hazen plot $W_n=\frac{2n-1}{2N}$ $F_n=1-W_x=1-\(\frac{2n-1}{2N}\)$ n : Number of observation (annual maximum series) P : Probability $P=\frac{N!}{{t!}(N-t)}F{_i}^{N-t}(1-F_i)^t$ $F_n$ : Thomas plot $F_n=\(1-\frac{n}{N+1}\)$ N : Total number of sample size $X_l$ : $X_s$ : maximum, minumum value of total number of sample size.

• 한국과학교육학회지
• /
• 제20권4호
• /
• pp.505-509
• /
• 2000

담화단위의 연관도를 측정하는 평균기본계수 $(\bar{B}_1)$, 평균가중계수 $(\bar{B}_2)$ 그리고 진행도 (P)는 다음과 같다. T1($\bar{B}_1$, 0.21: $\bar{B}_2$, 0.86: P. 0.79), T2($\bar{B}_1$, 0.02:$\bar{B}_2$, 0.85: P. 0.80), T3($\bar{B}_1$, 0.22: $\bar{B}_2$, 0.83: P.0.78) and T4($\bar{B}_1$, 0.14: $\bar{B}_2$, 0.82: P. 0.86), T4 교사는 다른 교사들에 비해 낮은 역동적 구조를 나타냈으나 수업은 빠른 진행도를 보였다. 총 담화단위 수, 어소의 총 빈도 수, 어소의 종류 수는 T1, T2, T3,T4 교사의 순으로 나타났다. 결과적으로 T4 교사는 다른 교사에 비해 수업 내용의 역동적 구조가 전체적으로 볼 때 낮은 수준을 보였는데, 그 주된 이유는 T4 교사는 수업 준비를 체계적으로 하지 않아, 수업내용이 상대적으로 적었기 때문으로 추측된다. 게다가 T4 교사가 담당하고 있는 학급이 1개 학급이기에 반복적인 수업이 이루어지지 않아 자기 분석의 기회가 없었고, 수업의 내용이 전공 영역과의 관련성이 적었으며 교직 경력 또한 다른 교사보다 낮았기 때문으로 사료된다.

• Journal of applied mathematics & informatics
• /
• 제39권1_2호
• /
• pp.155-163
• /
• 2021

For a connected graph G of order n, a set S of vertices is called a double geodetic set of G if for each pair of vertices x, y in G there exist vertices u, v ∈ S such that x, y ∈ I[u, v]. The double geodetic number dg(G) is the minimum cardinality of a double geodetic set. Any double godetic set of cardinality dg(G) is called a dg-set of G. A connected double geodetic set of G is a double geodetic set S such that the subgraph G[S] induced by S is connected. The minimum cardinality of a connected double geodetic set of G is the connected double geodetic number of G and is denoted by dgc(G). A connected double geodetic set of cardinality dgc(G) is called a dgc-set of G. Connected graphs of order n with connected double geodetic number 2 or n are characterized. For integers n, a and b with 2 ≤ a < b ≤ n, there exists a connected graph G of order n such that dg(G) = a and dgc(G) = b. It is shown that for positive integers r, d and k ≥ 5 with r < d ≤ 2r and k - d - 3 ≥ 0, there exists a connected graph G of radius r, diameter d and connected double geodetic number k.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.473-478
• /
• 2010

In this study, the Ergun's equation has been verified in order to calculate pressure drop of the two phase flow. The equation had been used in the high Reynolds number region for interior ballistic analysis in spite of being verified in the low Reynolds number region. Therefore additional verification seems to be inevitable. Thus, the validity of the equation has been verified using CFD in the high Reynolds number cases of the diameter-particle ratio 10, 13 and 16.

• Kyungpook Mathematical Journal
• /
• 제59권3호
• /
• pp.363-375
• /
• 2019

Let G = (V, E) be a simple graph with p vertices and q edges. A subset S of V (G) is called a strong (weak) efficient dominating set of G if for every $v{\in}V(G)$ we have ${\mid}N_s[v]{\cap}S{\mid}=1$ (resp. ${\mid}N_w[v]{\cap}S{\mid}=1$), where $N_s(v)=\{u{\in}V(G):uv{\in}E(G),\;deg(u){\geq}deg(v)\}$. The minimum cardinality of a strong (weak) efficient dominating set of G is called the strong (weak) efficient domination number of G and is denoted by ${\gamma}_{se}(G)$ (${\gamma}_{we}(G)$). A graph G is strong efficient if there exists a strong efficient dominating set of G. In this paper, some cycle and star related Nordhaus-Gaddum type relations on strong efficient dominating sets and the number of strong efficient dominating sets are studied.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2004년도 ICCAS
• /
• pp.383-388
• /
• 2004

This paper presents the aerodynamic coefficient modeling with a new model structure explored by Least Squares using Modulating Function Technique (LS/MFT) for an F-16XL airplane using wind tunnel data supplied by NASA/LRC. A new model structure for aerodynamic coefficient was proposed, one that considered all possible combination terms of angle of attack ${\alpha}$(t) and ${\alpha}$(t) given number of harmonics K, and was compared with Pearson's model, which has the same number of parameters as the new model. Our new model harmonic results show better agreement with the physical data than Pearson's model. The number of harmonics in the model was extended to 6 and its parameters were estimated by LS/MFT. The model output of lift coefficient with K=6 correspond reasonably well with the physical data. In particular, the estimation performances of four aerodynamic coefficients were greatly improved at high frequency by considering all harmonics included in the input${\alpha}$(t), and by using the new model. In addition, the importance of each parameter in the model was analyzed by parameter reduction errors. Moreover, the estimation of three parameters, i.e., amplitude, phase and frequency, for a pure sinusoid and a finite sum of sinusoids- using LS/MFT is investigated.

• 한국병원경영학회지
• /
• 제4권2호
• /
• pp.286-304
• /
• 1999

The purpose of the study was to analysis physician's prescribing behavior. Data was collected from 320 medical doctors of 10 general hospitals from August to September in 1996. The major findings are as follows; 1) Prescribing dosage: 74% of total selected middle dosage. Resident doctors used maximum dosage. 2) The number of similar antibiotics: 72.4% of total used 1 antibiotic. Surgery depts. and resident doctors selected 2, 3 antibiotics. Physicians to consider of insurance benefit or non insurance benefit used the number of antibiotics less than not to consider. Physicians to think over patient's economic state used less the number of antibiotics than that not to consider. 3) Used term of antibiotics: Total mean was 7.39 days. medical parts had 9.11 days but surgery used 6.41 days. Specialists consumed 6.57 days and residents applied 7.80 days. Physician to reflect result of claim used short term of antibiotics than that don't reflected. 4) Optional order of antibiotics: First antibiotics were selected 68% of total respondents, by medical depts, but secondary, tertiary antibiotics was used surgery depts. Tertiary antibiotics was used residents doctors, universal hospitals, fill beds and over. 5) The number of the items of oral drug : 3-4 the items of oral drug were used 76% of respondent Surgery parts selected 1-2 the items of oral drug, medical depts. selected five and over. Physician to reflect result of claim used less the number of the items of oral drug than that don't reflected. Physician to prescribe different of class of insurance used less the number of the items of oral drug than that don't prescribe different.

• Journal of Power Electronics
• /
• 제14권6호
• /
• pp.1157-1165
• /
• 2014

The T-type topology is a three-level topology that has an advantage in terms of its number of switching device and its efficiency when compared to the neutral-point clamped (NPC)-type topology. With the recent increase in the usage of the T-type topology, the interest in its reliability has also increased. Therefore, a tolerance control for a T-type rectifier is necessary to improve the reliability of applications when an open-switch fault occurs. NPC-type rectifiers cannot eliminate input current distortion completely. However, the T-type rectifier is able to restore distorted current. In this paper, a tolerance control for the $S_{x2}$ and $S_{x3}$ open-switch faults of a T-type rectifier is proposed where it is advantageous in terms of efficiency when compared with other tolerance controls. The performance of the proposed tolerance control is verified through simulation and experimental results.