• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.251-258
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• 2001

Cable and membrane structures can be classified as a unstable structure in the view point of shape determination process. An unstable stucture at the initial state generally cannot take a role as the resistance for the external force. Therefore, there should be a stabilizing process to get the stable state of a structure and it is necessary to visualize the shape finding from unstable state to stable state. In this paper, a numerical method of stabilizing procedure for the link structures is presented. The structures are assumed to have rigid movements and thus only changing of the topology of member is considered during the analysis. The generalized inverse matrix and the principle of minimum potential energy are used in the process. Illustrative examples are presented and the results show good convergence.

• The Journal of the Acoustical Society of Korea
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• v.18 no.2E
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• pp.39-44
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• 1999

In passive sonar, underwater moving objects are identified by the acoustic sounds they transmit. The spectrum of these sounds show features about the mechanism of the sound source, these features are discrete frequencies on the spectrum and frequency lines on the spectrogram. Variability in the underwater environment produce discontinuous broken or unstable fluctuating frequency lines. In this paper, we propose an efficient algorithm that estimate continuities of the discontinuous frequency lines and extract presence of the unstable frequency lines using neural networks and represent the proposed algorithm shows good performance in estimation and extraction the unstable frequency lines through the experiments.

• International Journal of Computer Science & Network Security
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• v.21 no.1
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• pp.64-69
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• 2021

In this paper, we have proposed a new internal model control structure (IMC). It is aimed at unstable overactuated multivariable systems whose transfer matrices are singular and unstable. The model inversion problem is essential to understand this structure. Indeed, the precision between the output of the process and the setpoint is linked to the quality of the inversion. This property is preserved in the presence of an additive disturbance at the output. This inversion approach proposed in this article can be applied to multivariable systems with no minimum phase or minimum phase shift with or without delays in their transfer matrices. It is proven by an example of simulation through which we have shown its good performance as a guarantee of stability, precision as well as rapidity of system responses despite the presence of external disturbances and we have tested this control structure in the frequency domain hence the robustness of the IMC.

• The Journal of the Korean dental association
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• v.38 no.3 s.370
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• pp.225-231
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• 2000

• PNF and Movement
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• v.16 no.2
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• pp.249-257
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• 2018

Purpose: This study aimed to explore the effects of additional trunk exercises on an unstable surface on the balance and walking ability of individuals with chronic stroke. Methods: Sixteen patients with chronic stroke participated in this study. The participants were randomly assigned to two groups: experimental group (n=8) and control group (n=8). All the participants underwent a typical physical therapy program for 30 min a day. Moreover, the experimental group participated in a 30 min trunk exercise program on an unstable surface, whereas the control group participated in a 30 min trunk exercise program on a stable surface. Both groups performed the exercises five times a week for three weeks. The Berg Balance Scale (BBS) was used to measure changes in balance. The gait variables were measured using the GAITRite system (CIR System Inc., Clifton, NJ, USA) to examine changes in walking ability. Results: Both groups showed a significant intragroup improvement in balance, gait speed, cadence, stride length, and double support period (p<0.05). In the intergroup comparisons after the intervention, the experimental group showed significant improvements over the control group in balance, gait speed, cadence, stride length, and double support period (p<0.05). Conclusion: This study applied additional trunk exercises on an unstable surface to chronic stroke patients, and the results showed a significant improvement in the patients' balance and walking abilities. Therefore, trunk exercise on an unstable surface may be applicable as an intervention method to improve the balance and walking ability of chronic stroke patients.

• Journal of The Korean Society of Integrative Medicine
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• v.6 no.3
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• pp.59-71
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• 2018

Purpose : The purpose of this study was to compare the effects of ankle balance training on unstable and stable surfaces to discover on which surface the proprioception, balance and muscle strength of obese middle aged women improves more. Method : Thirty obese middle-aged women were randomly recruited and divided into two groups (training on an unstable surface, training on a stable surface). The subjects in each group participated in the training for six weeks, three times per week for 30 minutes each session. Proprioception was measured using Dualer IQ digital inclinometer; sway length (SL) and sway area (SA) of center of pressure, and limit of stability (LOS) were measured for balance; muscle strength before and after the training was measured using manual muscle testing. Results : There were significant improvements in the subscales of the proprioception, balance and muscle strength in those who participated in ankle balance training on the unstable surface, and in those who participated on the stable surface. However, before and after the intervention, there were no differences between those who had the balance traning on the unstable surface and those who had the balance traning on the stable surface. Conclusion : Unstable and stable surface ankle balance training are both effective in improving the proprioception, balance and muscle strength of obese middle-aged woman.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.1
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• pp.59-67
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• 2012

Purpose : This study was somatosensory less in patients with idiopathic scoliosis somatosensory input to the lumbar stabilization exercises carried out to determine the most effective treatment method to be stable and unstable in terms of supporting the lumbar stabilization exercises the patient's torso length and postural sway by comparing the distance from a standing position and looked for differences in effect on the balance. Methods : The subjects of the study were 18 patients who showed the symptom of scoliosis. The study classified the patients into two experimental groups, one using an unstable surface and one a fixed surface, and the patients were required to do a lumbar stabilization exercise a total of 12 times for 60 minutes per session, three times a week for four weeks. The study carried out a paired comparison t-test so as to compare differences between measurement values in each experimental group before and after the exercise. Results : Superior iliac spine on the left, there was a significant reduction in the group doing the lumbar stabilization exercise on an unstable surface (p<0.05). Regarding change in sway distance to the left and right directions in the group doing the lumbar stabilization exercise on the unstable surface, there was a significant decrease in both the condition of closed eyes or open eyes (p<0.05). As for change in sway distance in forward-and-backward direction, there was a significant reduction in the condition of either closed eyes or open eyes (p<0.05). Conclusion : The lumbar stabilization exercise on an unstable surface improved the trunk posture of patients with scoliosis symmetrically, and the static balance ability in a standing posture was discovered to be improved. In the future, the lumbar stabilization exercise on an unstable surface may be used as a posture correction and balance increase exercise for patients with scoliosis.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.75-82
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• 2004

Many researcher's efforts have made a significant advancement of space frame structure with various portion, and it becomes the most outsanding one of space structures. However, with the characteristics of thin and long term of spacing, the unstable behavior of space structure is shown by initial imperfection, erection procedure or joint, especially space frame structure represents more. This kind of unstable problem could not be set up clearly and there is a huge difference between theory and experiment. Moreover, the discrete structure such as space frame has more complex solution, this it is not easy to derive the formulation of design about space structure. In this space frame structure, the character of rise-span ratio or load mode is represented by the instability of space frame structure with initial imperfection, and snap-through or bifurcation might be the main phenomenon. Therefore, in this study, space frame structure which has a lot of aesthetic effect and profitable for large space covering single layer is dealt. And because that the unstable behavior due to variation of inner force resistance in the elastic range is very important collapse mechanism, I would like to investigate unstable character as a nonlinear behavior with a geometric nonlinear. In order to study the instability. I derive tangent stiffness matrix using finite element method and with displacement incremental method perform nonlinear analysis of unit space structure, star dome and 3-ring star dome considering rise-span $ratio(\mu}$ and load $ratio(R_L)$ for analyzing unstable phenomenon.

• Clinics in Shoulder and Elbow
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• v.6 no.2
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• pp.131-137
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• 2003

Purpose: Unstable Neer type II lateral end fracture of clavicle may be required operation. The purpose of this study is the effectiveness of the use of Hook plate in the management of unstable Neer type II fractures. We preliminary reported the results of Unstable Neer type II lateral end fracture of clavicle using by Hook plate. Material and Methods: From May 1998 to May 2002, we operated 6 cases unstable Neer type II lateral end fracture of clavicle with Hook plate by one surgeon. We checked radiologic evaluation and disappearance of pain per 1 week, and evaluated improvement of range of motion per 2 week. And we followed up at each interval 3 months,6 months, 12 months and after that per 6months interval, at that each time we checked stress radiogram of shoulder and functional evaluation. The shoulder function was evaluated using Modified Shoulder Rating Scale (MSRC) for Distal Clavicle Fracture and UCLA score. Average follow up was on 37.2 (12∼57) months. Results: All 6 patients were regained satisfactory function. Average MSRC for distal clavicle fracture was 17.3 (15∼20) and average UCLA score was 33.2 (31∼35) at last follow up. Conclusion: There are many advantage of the use of Hook plate on management of unstable Neer II distal clavicle fracture in spite of several disadvantage. There have not yet been reported in our country. So we obtained good to excellent clinical result in surgical treatment of 6 cases on type II displaced lateral end fracture of the clavicle. But we think that more cases will be review and longer follow up will be needed in the future.

• The Journal of Korean Physical Therapy
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• v.29 no.2
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• pp.55-61
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• 2017

Purpose: The purpose of this study was to investigate the effects of a task-oriented upper arm exercise performed in a sitting position on either an unstable support surface or a stable support surface for children with cerebral palsy. Methods: We prospectively evaluated 18 children with cerebral palsy. Eight subjects were randomly assigned to each of the stable and unstable support surface groups. We performed the upper arm exercise three times a week for 6 weeks. To confirm the effects of the intervention, the berg balance scale test, modified functional reaching test (MFRT), timed up and go test (TUG), and Jebsen-Taylor hand function test were conducted before and after the study. Results: Significant differences were observed in MFRT and TUG between the experimental and control groups (p<0.05). In the Jebsen-Taylor hand function test, there were significant differences between the groups for the items picking up small objects, stacking checkers, lifting large light objects, and lifting large heavy objects (p<0.05), but not for writing and stimulation of feeding. Significant differences were observed between the groups in items of card turning, lifting large light objects, and lifting heavy objects. Conclusion: The purpose of this study was to evaluate the effectiveness of a task-oriented upper extremity exercise program for dynamic balance and hand function performed in a sitting position with either stable or unstable support by cerebral palsy patients. There were improvements in the two groups, but performing the exercise while sitting on an unstable support surface had a greater effect on dynamic balance and hand function than exercise while sitting on a stable supporting surface. The results of this study can be used to improve the daily lives of cerebral palsy patients.