• Journal of applied mathematics & informatics
• /
• 제29권1_2호
• /
• pp.279-292
• /
• 2011

In this paper, we consider anti-periodic solutions of the following BAM neural networks with multiple delays on time scales: $$\{{x^\Delta_i(t)=-a_i(t)e_i(x_i(t))+{\sum\limits^m_{j=1}}c_{ji}(t)f_j(y_j(t-{\tau}_{ji}))+I_i(t),\atop y^\Delta_j(t)=-b_j(t)h_j(y_j(t))+{\sum\limits^n_{i=1}}d_{ij}(t)g_i(x_i(t-{\delta}_{ij}))+J_j(t),}\$$ where i = 1, 2, ..., n,j = 1, 2, ..., m. Using some analysis skills and Lyapunov method, some sufficient conditions on the existence and exponential stability of the anti-periodic solution to the above system are established.

• 한국정밀공학회지
• /
• 제10권4호
• /
• pp.216-226
• /
• 1993

Three dimensional cutting is considered as an equivalent orthogonal cutting through the plane containing both the cutting velocity vector and the chip flow velocity vector in dynamic cutting process. An analytical expression of dynamic cutting force is obtained from the cutting parameters determined by the static cutting. Particular attention is paid to the energy supplied to the vibratory system of cutting tool with two degree of freedom. In this approach, the phase lag of the horizontal vibration of the tool behind the vertical vibration and the direction angle of the fluctuating cutting force is considered in point of stability limits. Chatter vibration can be effectively suppressed by relatively increasing the spring constant and the damping coefficient of the cutting system in the vertical cutting force direction. A good agreement is found between the stability limits predicted by theoretical value and experimental results.

• 충청수학회지
• /
• 제24권4호
• /
• pp.617-630
• /
• 2011

Let X, Y be vector spaces, and let r be 2 or 4. It is shown that if an odd mapping $f:X{\rightarrow}Y$ satisfies the functional equation $${\hspace{50}}rf(\frac{\sum_{j=1}^{d}\;x_j} {r})+\;{\sum\limits_{\iota(j)=0,1 \atop {\sum_{j=1}^{d}}\;{\iota}(j)=l}}\;rf(\frac{\sum_{j=1}^{d}{(-1)^{\iota(j)}x_j}}{r}) \\({\ddag}){\hspace{160}}=(_{d-1}C_l-_{d-1}C_{l-1}+1)\;{\sum\limits_{j=1}^{d}\;f(x_j)}$$ then the odd mapping $f:X{\rightarrow}Y$ is additive, and we prove the Cauchy-Rassias stability of the functional equation in Banach modules over a unital $C^*$-algebra. As an application, we show that every almost linear bijection $h:{\mathcal{A}}{\rightarrow}{\mathcal{B}}$ of a unital $C^*$-algebra ${\mathcal{A}}$ onto a unital $C^*$-algebra ${\mathcal{B}}$ is a $C^*$-algebra isomorphism when $h(2^nuy)=h(2^nu)h(y)$ for all unitaries $u{\in}{\mathcal{A}}$, all $y{\in}{\mathcal{A}}$, and $n=0,1,2,{\cdots}$.

• 한국추진공학회지
• /
• 제21권1호
• /
• pp.63-71
• /
• 2017

메탄($CH_4$)/산소($O_2$) 액체이원추진제는 친환경성, 무독성, 경제성, 우수한 성능 등의 장점으로 최근 들어 차세대 친환경 이원추진제로서 관심을 받고 있다. 본 연구에서는 연소실 내 압력 변화에 따른 기체 메탄/산소 비예혼합 동축 화염의 연소안정한계를 측정하고, 화염 및 유동의 가시화를 통해 분사 조건 및 압력 변화에 따른 화염의 구조와 특성을 파악하였다. 연구 결과 연료과농 조건에서 연소실 내 압력이 증가할 경우 연소안정한계가 확장되고 반응 영역이 증가하는 것을 확인할 수 있었다.

• 대한통합의학회지
• /
• 제9권3호
• /
• pp.69-78
• /
• 2021

Purpose : The purpose of this study was to investigate the effect of stair exercise and Kegel combined exercise on the maximum voluntary ventilation (MVV) and limits of stability (LOS). Methods : 23 female students participated in this experiment. MVV was measured with a spirometer. The LOS was measured with a Biorescue. Subjects were randomly assigned to two groups. 12 subjects were assigned to the experimental group and 11 subjects were assigned to the control group. The experimental group performed 5 minutes of stair exercise and 5 minutes of Kegel exercise. The control group performed 10 minutes of stair exercise. After 5 minutes of exercise, 1 minute of rest was provided. Both groups exercised for 5 minutes according to the metronome beat 130 during the stair exercise. After 5 minutes of rest after exercise, MVV and LOS were measured again in the same way. The measurement sequence was also randomly alternated. Results : Significant differences were found within and between groups in the experimental group in MVV (p<.05). In LOS, significant differences were confirmed in left, right, forward, backward, and total LOS in the experimental group (p<.05). In the control group, there were significant differences in left, forward, and total LOS (p<.05). However, there was no significant difference between groups (p>.05). Conclusion : Based on the results of this study, it was confirmed that the stairs and Kegel combined exercise had a positive effect on MVV and LOS. However, in the short term, it was found that the stair and Kegel combined exercise was insufficient in time and the threshold of exercise to show the difference between groups in LOS. Therefore, additional research should be conducted by modifying the limitations of this study.

• Journal of Magnetics
• /
• 제20권1호
• /
• pp.52-56
• /
• 2015

The purpose of the current study was to investigate the effect of repetitive transcranial magnetic stimulation (rTMS) in conjunction with mirror therapy on the balance function of patients with sub-acute stroke hemiparesis. This study was conducted with 36 subjects who were diagnosed with a hemiparesis due to stroke. Participants in the experimental (19 members) and control groups (17 members) received rTMS and sham rTMS during 10 minute sessions each, which were carried out five days per week for four weeks. This was followed by the mirror therapy over 30 minute sessions, which were carried out five days per week for four weeks. Motor recovery was assessed by balance index, dynamic limits of stability, Berg balance scale, and time up go test. The change values of the balance index ($-2.06{\pm}1.99$ versus $-0.41{\pm}1.11$), dynamic limits of stability ($3.68{\pm}2.71$ versus $1.17{\pm}2.38$), and time up go test ($-7.05{\pm}5.64$ score versus $-3.35{\pm}5.30$ score) were significantly higher in the experimental group than in the control group (p < 0.05). At post-test, balance index ($4.08{\pm}1.14$ versus $5.09{\pm}1.04$), dynamic limits of stability ($13.75{\pm}0.60$ versus $11.73{\pm}3.53$), and time up go test ($23.89{\pm}4.51$ versus $28.82{\pm}3.07$) were significantly higher in the experimental group than in the control group (p < 0.05). In the experimental group, significant differences were found in the pre- and post-test scores for the balance index, dynamic limits of stability, Berg balance scale, and time up go test (p < 0.01). In the control group, a significant difference was observed between the pre- and post-test only for the Berg balance scale and time up go test (p < 0.05). These findings demonstrate that the application of 1Hz rTMS in conjunction with mirror therapy can be helpful in improving the balance function of patients with sub-acute stroke hemiparesis, and this may be used as a practical adjunct to routine rehabilitation therapy.

• 대한수학회논문집
• /
• 제26권1호
• /
• pp.99-113
• /
• 2011

In this paper, we investigate the stability using shadowing property in Abelian metric group and the generalized Hyers-Ulam-Rassias stability in Banach spaces of a quadratic functional equation, $f(x_1+x_2+x_3+x_4)+f(-x_1+x_2-x_3+x_4)+f(-x_1+x_2+x_3)+f(-x_2+x_3+x_4)+f(-x_3+x_4+x_1)+f(-x_4+x_1+x_2)=5{\sum\limits_{i=1}^4}f(x_i)$. Also, we study the stability using the alternative fixed point theory of the functional equation in Banach spaces.

• 한국콘텐츠학회논문지
• /
• 제18권11호
• /
• pp.348-352
• /
• 2018

BioRescue($RMIng{\acute{e}}nierie$, Marseille, France)는 대상자가 일어서거나 앉을 때 동적과 정적인 균형을 평가하기 위해 사용하는 장비이다. 이전부터 다양하게 사용되고 있지만 이 장비에 대한 명확한 신뢰도에 대한 연구는 아직 부족한 상태이다. 본 논문은 균형 능력 측정을 위한 BioRescue의 측정자내와 측정자간 신뢰도를 측정했다. 이 연구의 대상자는 34명의 건강한 대상자들과 2명의 물리치료사 평가자들로 구성되었다. BioRescue는 발지표(면적과 압력), 롬버그 검사, 안정성 검사로 구성되어 있다. 발지표의 면적과 안정성 검사는 모든 방향에서 ICC값이 0.60 이상으로 나왔다. 하지만 발지표의 압력과 롬버그 검사는 모든 방향에서 ICC값이 0.60 이하로 나왔다. BioRescue는 균형검사 시 발지표의 면적과 안정성 검사에서 높은 신뢰도를 나타냈다. 하지만, 발지표의 압력과 롬버그 검사의 수치에서 숙련자와 비숙련자의 차이를 보이기 때문에 장비의 정확성을 위해 숙련이 필요하다.

• 대한전기학회논문지:전력기술부문A
• /
• 제51권11호
• /
• pp.535-543
• /
• 2002

Modern power grids are becoming more and more stressed with the load demands increasing continually. Therefore large stressed power systems exhibit complicated dynamic behavior when subjected to small disturbance. Especially, it is needed to analyze special conditions which make small signal stability structure varied according to operating conditions. This paper shows that the relation between small signal stability structure varied according to operating conditions. This paper shows that the relation between small signal stability and operating conditions can be identified well using node-focus point and 1:1 resonance point. Also, the weak point which limits operating range is found by the analysis of resonance condition, and it is shown that reactive power compensation may solve the problem in the weak points. The proposed method is applied to test systems, and the results illustrate its capabilities.

• 한국전기전자재료학회논문지
• /
• 제30권8호
• /
• pp.530-534
• /
• 2017

Transparent film heaters employing silver nanowires (Ag NWs) have attracted increasing attention because of their widespread applications. However, the low thermal resistance of Ag NWs limits the maximum operating temperature of the Ag NW film heater. In this study, Ag NW film heaters with high mechanical and thermal stability were successfully developed. The thermal power-out characteristics of the Ag NW heaters were investigated as a function of the Ag NW density. The results revealed that the prepared flexible Ag NW heater possessed high thermal stability over $190^{\circ}C$ owing to ZnO encapsulation. This indicates that the Ag NW film with excellent thermal stability have remarkably high potential for use as electrodes in film heaters operating at high temperatures.