• 한국치위생학회지
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• 제15권1호
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• pp.91-99
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• 2015

Objectives: The purpose of the study was to investigate the relationship between internet addiction and health in dental hygiene students. Methods: A self-reported questionnaire was completed by 216 dental hygiene students in Daegu from June 9 to 13, 2014. Data were analyzed by descriptive statistics, t-test, and ANOVA using SAS 9.2 program. The instruments included Korean internet addiction scale(K scale) and Korean version of the general health questionnaire. General characteristics consisted of grade, religion, residential types, economic condition, place of internet use, duration, purpose, and time of use. Physical characteristics consisted of subjective physical condition, smoking, alcohol drinking, exercise above twice per week, musculoskeletal disease, and location of physical symptoms. Psychiatric scale and 6 questions of physical characteristics were consulted by the statistician of preventive medicine department. Results: Internet users over 4 hours manifested the poor mental health, while those who uses internet under 2 hours showed good mental health(F = 1.41, p < 0.01). The students having good physical condition showed better mental health than those with poor physical condition(t = -2.81, p < 0.01). The students exercising at least twice a week showed better mental health than those who do not exercise(t = -3.10, p < 0.01). Those who having musculoskeletal symptoms showed higher index of internet addiction score than those who do not(t = 4.21, p < 0.01). Those who have no musculoskeletal symptoms tended to have better mental health than those who have musculoskeletal symptoms(t = 2.28, p < 0.05). The variables correlated to mental health were internet addiction, subjective physical condition, and exercise at least twice a week. The severity level of internet addiction leads to poor mental health(r = 0.26, p < 0.001). Conclusions: Internet addiction is closely related to mental health. So the students must know the danger of internet addiction. Proper health education is necessary for the prevention of addiction symptoms.

• 대한수학회보
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• 제22권2호
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• pp.95-98
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• 1985

In [1], E.B. Lee and L. Markus described a sufficient condition for which the domain of null-controllability of a linear autonomous system is all of R$^{n}$ . The purpose of this note is to extend the result to a certain linear nonautonomous system. Thus we consider a linear control system dx/dt = A(t)x+B(t)u in the Eculidean n-space R$^{n}$ where A(t) and B(t) are n*n and n*m matrices, respectively, which are continuous on 0.leq.t<.inf. and A(t) is a periodic matrix of period .omega.. Admissible controls are bounded measurable functions defined on some finite subintervals of [0, .inf.) having values in a certain convex set .ohm. in R$^{m}$ with the origin in its interior. And we present a sufficient condition for which the domain of null-controllability is all of R$^{n}$ .

• 대한기계학회논문집A
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• 제33권10호
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• pp.1065-1073
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• 2009

In this paper, the estimation method of C(t)-integral for combined mechanical and thermal loads is proposed for elastic-plastic-creep material via 3-dimensional FE analyses. Plasticity induced by initial loading makes relaxation rate different from those produced elastically. Moreover, the interactions between mechanical and thermal loads make the relaxation rate different from those produced under mechanical load alone. To quantify C(t)-integral for combined mechanical and thermal loads, the simplified formula are developed by modifying redistribution time in existing work done by Ainsworth et al..

• 한국전기전자재료학회논문지
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• 제19권2호
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• pp.126-129
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• 2006

We investigated an optimized condition of the capacitor threshold voltage implantation(capacitor $V_T$ Implant) in planar P-MOS DRAM Cell. Several samples with different condition of the capacitor $V_T$ Implant were prepared. It appeared that for the capacitor $V_T$ Implant of $BF_2\;2.0{\times}l0^{13}\;cm^{-2}$ 15 KeV, refresh time is three times larger than that of the sample, in which capacitor $V_T$ Implant is in $BF_2\;1.0{\times}l0^{13}\;cm^{-2}$ 15 KeV. Raphael simulation revealed that the lowed maximum electric field and lowed minimum depletion capacitance ($C_{MIN}$) under the capacitor resulted in well refresh characteristics.

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1109-1118
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• 2009

In this paper, we are concerned with the following four point boundary value problem with one-dimensional p-Laplacian, $\{({\phi}_p(x'(t)))'+h(t)f(t,x(t),|x'(t)|)=0$, 0< t<1, $x'(0)-{\delta}x(\xi)=0,\;x'(1)+{\delta}x(\eta)=0$, where $\phi_p$ (s) = |s|$^{p-2}$, p > $\delta$ > 0, 1 > $\eta$ > $\xi$ > 0, ${\xi}+{\eta}$ = 1. By using a fixed point theorem in a cone, we obtain the existence of at least three symmetric positive solutions. The interesting point is that the boundary condition is a new Sturm-Liouville-like boundary condition, which has rarely been treated up to now.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2023년도 춘계학술대회
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• pp.51-51
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• 2023

Global warming has significant effects on the growth and development of wheat and can cause a reduction in grain yield and quality. Grain quality is a major factor determining the end-use quality of flour and a reduction in quality can result economic losses. Therefore, it is necessary to study the physiological characteristic of wheat to understand its response to temperature elevation, which can aid in the development of strategies to mitigate the negative effects of high temperature and sustain wheat production. This study investigated the effects of elevated temperature on grain characteristics and quality during the grain filling period of two Korean bread wheat cultivars Baekkang and Jokyoung. These two bread wheat cultivars were subjected to an increasing temperature conditions regime; T0 (control), T1 (T0+1℃), T2 (T0+2℃) and T3 (T0+3℃). The results showed that high temperature, particularly in T3 condition, caused a significant decrease in the number of grains per spike and grain yield compared to the T0 condition. The physical properties, such as grain weight and hardness, as well as chemical properties, such as starch, protein, gluten content and SDSS, which affect the quality of wheat, were changed by high temperature during the grain filling period. The grain weight and hardness increased, while the grain size not affected by high temperature. On the other hand, amylose content decreased, whereas protein, gluten content and SDSS increased in T3 condition. In this study, high temperature within 3℃ of the optimal growth temperature of wheat, quantity properties decreased while quality-related prosperities increased. To better understand the how this affects the grain's morphology and quality, further molecular and physiological studies are necessary.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.10-13
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• 2005

Transport current and magnetic field which is generated by transport current make AC current - AC mag-netic field condition(AC-AC condition) in AC power application system using HTS tape. Therefore, characteristics of AC loss under the AC-AC condition are necessary to estimate AC loss of power device with accuracy such as HTS transformer. In this paper, we researched transport current loss, magnetization loss by perpendicular magnetic field and total loss which is represented as summation of both losses under the AC-AC condition in single HTS tape. As a result, magnetization loss showed increasing behavior under 65mT and decreasing behavior upper 65mT by influence of transport current. Transport current loss was increased continuously through out whole measurement ranges in the AC-AC condition. Total loss in HTS tape was dominated entirely by magnetization loss.

• 인지과학
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• 제27권2호
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• pp.275-301
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• 2016

주의깜박거림(AB)이란 시야의 고정 위치에 신속순차제시(RSVP)되는 항목들 중에 출현하는 두 표적에 대해 후행 표적(T2)이 선행 표적(T1)의 출현 이후 약 500ms 이내에 출현할 경우 그에 대한 의식적 수준의 보고가 어려워지는 현상을 의미한다. 본 연구는 T1 기억공고화에 요구되는 주의자원량이 T2에 대한 AB 강도를 결정한다는 병목 모형을 토대로 T1에 대한 표적 가시성 처치가 T2에 대한 주의깜박거림의 강도에 미치는 영향을 조사하였다. T1 저가시성 조건의 경우 T1에 배경화면과의 명암대비가 낮은 회색을 그리고 T1 고가시성 조건의 경우 선명한 색상을 부여해 흰색의 나머지 방해자극들과 구분되도록 처치하였다. 또한 표적 위치에 대한 불확실성 부여를 위해 시야의 네 위치에 전개되는 다중 RSVP 배열 내에 T1과 T2를 제시해 표적처리에 관여하는 주의 자원을 평균적으로 소진시켰다. 두 편의 실험에서 T2에 대한 AB의 강도는 고가시성 조건에서 상대적으로 큰 것이 관찰되었으며 T2의 가시성을 증가시켰을 때 T1 가시성 처치의 영향력이 더욱 분명해졌다. 이러한 결과는 T1 병목 해소를 위해 할당되는 가용한 주의 자원의 양이 부족할수록 더욱 T1 가시성 효과의 영향력이 분명해짐을 시사하며, T1의 가시성 수준이 T1 병목의 강도를 결정할 수 있다는 병목 모형의 제안을 지지한다.

• 한국항공우주학회지
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• 제38권7호
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• pp.664-672
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• 2010

본 논문은 표적의 방향 정보만을 측정할 경우 $t_{go}$-다항식 유도법칙의 표적 가관측성 분석을 다룬다. 본 연구에서는 직접적인 방법으로 표적의 가관측성을 분석한다. 등속도 표적에 대해 가관측성을 갖기 위한 조건들이 시선각의 함수로만 주어지기 때문에, $t_{go}$-다항식 유도법칙을 적용 했을 때 시선각의 닫힌 해를 도출하고, 이 닫힌 해를 가관측성 조건에 직접 대입하므로, $t_{go}$-다항식 유도법칙의 표적 가관측성 특성을 해석한다. 표적의 가관측성은 유도법칙의 유도이득, 초기 유도 조건과 유도명령의 형상에 따라 달라진다. 최종적으로 시뮬레이션을 통해 $t_{go}$-다항식 유도법칙의 표적 가관측성을 검증한다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제34권5호
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• pp.532-536
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• 2008

Purpose: This study was designed to evaluate effect of EMD on proliferation of HPDLCs and MC3T3-E1 cells in high glucose condition in vitro. Material and method: The Human PDL fibroblasts(HPDLCs) were obtained through typical way and the cells used in this experiment were divided in 4 groups. $1{\times}10^4/ml$ HPDLCs suspension was cultured in typical DMEM and assigned to group 1. The cells cultured in DMEM which included 400mg/dl glucose are allocated to group 3. Group 2 and 4 are established by adding EMD to group 1 and 3 respectively. These control and experimental groups had been cultured for 24 and 48 hours, and MTT assay was conducted. The differences of each group in cellular proliferation was evaluated. The same experiment was conducted for preosteoblast (MC3T3-E1) with adding $25\;{\mu}g/ml$ EMD. Results: EMD had the same effect on both PDL cells and MCT3T3-E1 cells. The experimental group had more meaningful differences and active cellular proliferation than the control group did. The EMD accelerated cellular proliferation not only in normal glucose condition but also in high glucose condition. The same results were observed via MTT assay; EMD-added experimental group had more meaningful differences and showed higher cellular activity than control group did. Each experimental and control group was inspected for statistical significance through Kruskal-Wallis Test. Statistical significances were observed among these groups. (SPSS 12.0 Chicago, IL, USA, p=0.008, p=0.011) Conclusion: EMD is considered to accelerate proliferation of PDL cells and MC3T3-E1 cells in high glucose condition as well as normal glucose condition.