• Structural Engineering and Mechanics
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• 제87권4호
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• pp.363-373
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• 2023

Since the first family of structure-dependent methods can simultaneously integrate unconditional stability and explicit formulation in addition to second order accuracy, it is very computationally efficient for solving inertial problems except for adopting auto time-stepping techniques due to no nonlinear iterations. However, an unusual stability property is first found herein since its unconditional stability interval is drastically different for zero and nonzero damping. In fact, instability might occur for solving a damped stiffness hardening system while an accurate result can be obtained for the corresponding undamped stiffness hardening system. A technique of using a stability factor is applied to overcome this difficulty. It can be applied to magnify an unconditional stability interval. After introducing this stability factor, the formulation of this family of structure-dependent methods is changed accordingly and thus its numerical properties must be re-evaluated. In summary, a large stability factor can result in a large unconditional stability interval but also lead to a large relative period error. As a consequence, a stability factor must be appropriately chosen to have a desired unconditional stability interval in addition to an acceptable period distortion.

• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.396-403
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• 2016

PURPOSE. Early loading of implant can be determined by excellent primary stability and characteristic of implant surface. The implant system with recently improved surface can have load application 4-6 weeks after installing in maxilla and mandible. This study evaluated the effect of healing period to the stability of hydrophilic tapered-type implant at maxillary posterior area. MATERIALS AND METHODS. This study included 30 patients treated by hydrophilic tapered-type implants (total 41 implants at maxilla) and classified by two groups depending on healing period. Group 1 (11 patients, 15 implants) was a control group and the healing period was 12 weeks, and Group 2 (19 patients, 26 implants) was test group and the healing period was 6 weeks. Immediately after implant placement, at the first impression taking, implant stability was measured using Osstell Mentor. The patients also took periapical radiographs after restoration delivery, 12 months after restoration and final followup period. The marginal bone loss around the implants was measured using the periapical radiographs. RESULTS. All implants were survived and success rate was 97.56%. The marginal bone loss was less than 1mm after 1 year postoperatively except the one implant. The stabilities of the implants were not correlated with age, healing period until loading, insertion torque (IT), the diameter of fixture and the location of implant. Only the quality of bone in group 2 (6 week) was correlated with the stability of implant. CONCLUSION. Healing period of 6 weeks can make the similar clinical prognosis of implants to that of healing period of 12 weeks if bone quality is carefully considered in case of early loading.

• 한국광학회지
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• 제12권6호
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• pp.507-510
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• 2001

간단한 비선형 증폭 루프에서의 평균 솔리톤 전송의 안정성을 비선형 Schroedinger방정식에 기초한 수치해석법을 이용하여 솔리톤 주기에 대한 증폭 주기의 비율과 루프에서의 erbium doped광섬유의 길이 비율을 변화시켜가며 계산하고 그 결과를 분석하였다. 계산 결과 루프에서의 erbium doped광섬유의 길이 비율이 작을 경우 증폭 주기가 솔리톤 주기에 비해 많이 작아야 한다는 기존의 평균 솔리톤 형성 조건이 완화됨을 알 수 있었다.

• 전기의세계
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• 제21권2호
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• pp.20-24
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• 1972

The transient stability of the synchronous motor is generally improved by damper winding or flywheel. However the synchronous motor at full load will be pulled out from normal operation state when the period of power failure exceeds approximately ten cycle per second. This paper studies the method of improving the stability of synchronous motor by equipping the phase slipping switch between the motor and power source. This paper shows the motor does not pull out, which results from the decrease of power angle to about 30 electrical degrees by means of the switch even when the relatively long period of power failure brings the power angle to some 150 electrical degrees.

• 대한기계학회논문집B
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• 제26권1호
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• pp.94-100
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• 2002

The effects of periodic fuel supply on the nonpremixed flame stability and soot formation were experimentally studied. A solenoid valve was used to control the period of fuel supply. The laser induced incandescence technique was used to visualize cool: volume fraction profile. The flame base shape was changed significantly by the fuel supply period and partially by the fuel flowrates. The portion of bluish flame near the flame base became larger as the period increased. When the period was long, two flames coexisted within one period. It seemed that the characteristic of flame stability were repeated with 4.68m change of fuel supply line length. The soot mass measurements and soot volume fraction measurements revealed that the maximum suppression of soot by the perioic fuel supply was approximately 75% , which occurred when the occurred when the fuel supply period was relatively long.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1866-1888
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• 2017

Efficient energy consumption in WSN is one of the key design issues for improving network stability period. In this paper, we propose a new Heterogeneity-aware Energy-efficient Clustering (HEC) technique which considers two types of heterogeneity - network lifetime and of sensor nodes. Selection of cluster head nodes is done based on the three network lifetime phases: only advanced nodes are allowed to become cluster heads in the initial phase; in the second active phase all nodes are allowed to participate in cluster head selection process with equal probability, and in the last dying out phase, clustering is relaxed by allowing direct transmission. Simulation-based performance analysis of the proposed technique as compared to other relevant techniques shows that HEC achieves longer stable region, improved throughput, and better energy dissipation owing to judicious consumption of additional energy of advanced nodes. On an average, the improvement observed for stability period over LEACH, SEP, FAIR and HEC- with SEP protocols is around 65%, 30%, 15% and 17% respectively. Further, the scalability of proposed technique is tested by varying the field size and number of sensing nodes. The results obtained are found to be quite optimistic. The impact of energy heterogeneity has also been assessed and it is found to improve the stability period though only upto a certain extent.

• 품질경영학회지
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• 제50권3호
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• pp.473-490
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• 2022

Purpose: The purpose of this study is to propose a new useful suggestion to monitor the stability of process by developing a stability ratio or index related to investigating how well the process is controlled or operated to the specified target. Methods: The proposed method to monitor the stability of process is building up a new measure index which is making up for the weakness of the existing index in terms of short or long term period of production. This new index is a combined one considering both stability and capability of process to the specification limits. We suppose that both process mean and process variation(or deviation) are changing on time period. Results: The results of this study are as follows: regarding the stability of process as well as capability of process, it was shown that two indices, called SI(stability index) and PI(performance index), can be expressed in two-dimensional X-Y graph simultaneously. This graph is categorized as 4 separated partitions, which are characterized by its numerical value intervals of SI and PI which are evaluated by test statistics. Conclusion: The new revised index is more robust than the existing one in investigating the stability of process in terms of short and long period of production, even in case both process mean and variation are changing.

• 수산해양기술연구
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• 제45권4호
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• pp.267-275
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• 2009

According to the recent statistics of marine casualties in Korea, fishing boats are more likely to be ended in the casualties, and small fishing boats especially cause much more accidents in sinking and capsizing than any other big vessels. These casualties were mainly produced from the ignorance on the lack of own ship stability. From this view, this study aims to analyze the characteristics of stability on the crab trap fishing boat receiving transverse wave by means of carrying out the water tank test. The rolling angle of the model ship was affected largely with the displacement and the wave period of it, and the trends were shown that the magnitude of the angle was proportional to the displacement, but inversely to the wave period. And the wave height had effect on the rolling angle just in the specific range of the wave period. The force of steady wind didn't have influence on the rolling variation significantly.

• 한국항공우주학회지
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• 제34권4호
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• pp.25-32
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• 2006

현대의 고성능 전투기는 공력성능 및 조종성능의 향상을 위하여 대부분 세로축 방향으로 항공기를 불안정하게 설계하는 정안정성 완화(Relaxed Static Stability) 개념을 채택하고 있다. 비행제어법칙의 설계 작업은 불안정하게 설계된 항공기에 안정성(Stability)을 부여하고, 주어진 비행임무에 대하여 만족스런 조종성능(Controllability)을 발휘할 수 있도록 비행성능을 조작하는 일련의 과정이다. 항공기의 세로축 운동은 장주기 및 단주기 운동이라는 2개의 감쇠진동 모드가 중첩되어 있다고 간주한다. 전투기에서 세로축 제어법칙설계는 장주기 모드가 설계대상으로 고려되지 않으며, 미 군사규격인 MIL-F-8785C에 정의되어 있는 단주기 모드(Short Period Mode)의 요구조건을 이용하여 주파수와 감쇠비를 최적화한다. 이 때, 제어법칙이 포함된 고차시스템을 저차 등가시스템으로 등가 시켜 판별한다. 현재까지 항공기의 단주기 운동 특성에 관한 연구는 활발하게 진행되어 왔으나, 장주기 운동 특성에 관한 연구는 그렇지 못하였다. 본 논문에서는 T-50 훈련기의 장주기 모드 운동 특성을 분석하기 위해 선형 및 비선형해석을 수행하였으며, 받음각제한기 및 자동 피치자세각 트림 명령이 세로축 운동에 미치는 영향성을 분석하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.518-528
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• 2008

Purpose: The long-term experience of using osseointegrated implants for prosthetic rehabilitation of the edentulous patients shows that high success rates can be predictably achieved. Primary implant stability has been identified to be a prerequisite to achieve osseointegration. In this study, we set up the amount of removed bone so that it differed on implant installation site for each group. The influence of each initial stability on secondary stability and osseointegration was compared with time lapse using resonance frequency analysis and histomorphometric analysis. Materials and methods: A total 27 US $II^{(R)}$ (Osstem, Korea) implants were placed in the mandibular edentulous area of 3 beagle dogs. The implant site was prepared by the conventional technique with drills, and three experimental groups were divided into under-drilling group, normal-drilling group and over-drilling group. The Implant Stability Quotient (ISQ) was measured at intervals of immediately, 4, 8, 12 weeks after placement using $Osstell^{(R)}$ mentor RFA. After the animals were sacrificed, histomorphometric evaluation was executed for measuring BIC and BD. Results: 1) The under-drilled group showed most high ISQ value for whole experiment period. 2) Bone-to-implant-contact(BIC) showed the tendency to be increased gradually as the experiment period passed except the 8 weeks of the normal group. 3) The under-drilled group showed most high bone density(BD) level for whole experiment period, and it was expressed the aspect to be increased gradually according to an experiment period passage in the average of all group. 4) Resonance frequency analysis and histomorphometric analysis are presumed by generally proportional. Conclusions: As this research result, it seems that there are some correlation between resonance frequency analysis and histomorphometric analysis. As are accomplished osseointegration stably so that more superior at the region which the overpressure comes to add, it will be applicable method in clinical field.