• 한국산학기술학회논문지
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• 제13권9호
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• pp.4277-4283
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• 2012

고장력볼트 마찰이음에서 접촉면의 표면상태에 따라 다양한 값을 갖는 미끄러짐계수는 볼트의 축력과 미끄러짐하중에 의해 결정되어진다. 또한 접촉면적은 미끄러짐하중에 영향을 미치게 되므로 볼트구멍에 따라 변하는 접촉면적은 미끄러짐계수와 상관관계를 갖게 된다. 본 연구에서는 부재의 종류, 볼트의 직경 및 볼트구멍의 크기에 따른 미끄러짐계수와 미끄러짐하중의 변화를 파악하기 위하여 32개의 시험편을 제작하여 휨시험 및 인장시험을 실시하였다. 과대볼트구멍으로 제작된 시험편의 미끄러짐하중은 표준볼트구멍으로 제작된 미끄러짐하중의 80%이상의 강도를 발휘하였으며 설계 미끄러짐강도를 상회하였다. 또한 과대볼트구멍으로 제작된 시험편과 표준볼트구멍으로 제작된 시험편의 순단면적비와 미끄러짐비간에는 상당한 상관성을 가지는 것으로 나타났다. 그러나 시험결과가 각 시험체에 따라 다소의 차이를 보이는 것은 미끄러짐계수의 중요한 파라메타인 고장력볼트의 도입축력이 감소하기 때문인 것으로 판단된다. 볼트구멍 크기의 증가는 미끄러짐 계수 뿐 아니라 볼트 축력의 감소를 야기시키므로 설계강도의 감소를 초래하는 것은 자명한 사실이지만 외국의 경우와 같이 구조적 안정을 위협하지 않는 범위 내에서 볼트구멍에 대한 규정에 유연성을 갖는 것도 시공성과 효율성에 긍정적인 요소가 될 것으로 기대된다.

• 농업과학연구
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• 제48권4호
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• pp.815-829
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• 2021

The purpose of this study is to construct a flatfish outlook model that is consistent with the "Fisheries outlook" monthly publication of the fisheries outlook center of the Korea Maritime Institute (KMI). In particular, it was designed as a partial equilibrium model limited to flatfish items, but a model was constructed with a dynamic ecological equation model (DEEM) system, considering biological breeding and shipping times. Due to limited amounts of monthly data, the market equilibrium price was calculated using a recursive model method as the inverse demand. The main research results and implications are as follows. As a result of estimating young fish inventory levels, the coefficient of the young fish inventory in the previous period was estimated to be 0.03, which was not statistically significant. Because there is distinct seasonality, when estimating the breeding outcomes, the elasticity of breeding in the previous period was found to exceed 0.7, and it increased more as the weight of the fish increased, in addition, the shipment coefficient gradually increased as the weight increased, which means that as the fish weight increased, the shipment compared to the breeding volume increased. When estimating shipments, the elasticity of breeding in previous period was estimated to respond elastically as the weight increases. The price flexibility coefficient of the total supply was inelastically estimated to be -0.19. Finally, according to a model predictive power test, the Theil U1 was estimated to be very low for all of the predictors, indicating excellent predictive power.

• 한국의류학회지
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• 제23권6호
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• pp.898-908
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• 1999

This paper was aimed to identify the hand and sensibility of silk woven fabrics for neckties to find their relationships to the hand and purchasing preferences and to make their image scale. 56 male and female students evaluated 20 specimens with semantic differential scale of 21 hand and 25 sensibility adjectives. Data were analyzed through factor analysis pearson correlational coefficient t-test using PC SAS package. the hand adjectives were grouped as 4 surface property thermal property flexibility and dryness. The sensibility adjectives were modern classic character and natural,. The flat fabrics with warm hand displayed 'modern' sensibility but those with col hand show 'classic' The rough fabrics with warm hand showed 'natural' but those with cool hand showed 'character' The fabrics rated as high hand preference and purchasing preference showed soft and flat hand occuring 'modern' and 'classic' sensibility.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.605-638
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• 2015

It is intended to perform buckling analysis of steel gabled frames with tapered members and flexible connections. The method is based on the exact solutions of the governing differential equations for stability of a gabled frame with I-section elements. Corresponding buckling load and subsequently effective length factor are obtained for practical use. For several popular frames, the influences of the shape factor, taper ratio, span ratio, flexibility of connections and elastic rotational and translational restraints on the critical load, and corresponding equivalent effective length coefficient are studied. Some of the outcomes are compared against available solutions, demonstrating the accuracy, efficiency and capabilities of the presented approach.

• 한국소음진동공학회논문집
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• 제13권4호
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• pp.290-299
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• 2003

This paper presents an efficient modeling and dynamic analysis method for open cracked rotor bearing systems. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of cracks. The proposed modeling method is validated through a series of simulations and experiments. First, the proposed method Is rigorously compared with a commercial finite element code. Then, an experiment is performed to validate the proposed modeling method. Finally, a numerical example is introduced to demonstrate the possible application of the proposed method in the crack diagnosis for rotor systems.

• Smart Structures and Systems
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• 제5권5호
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• pp.507-515
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• 2009

The present work is an alternative methodology in order to balance a nonlinear highly flexible rotor by using neural networks. This procedure was developed aiming at improving the performance of classical balancing methods, which are developed in the context of linearity between acting forces and resulting displacements and are not well adapted to these situations. In this paper a fully experimental procedure using neural networks is implemented for dealing with the adaptive balancing of nonlinear rotors. The nonlinearity results from the large displacements measured due to the high flexibility of the foundation. A neural network based meta-model was developed to represent the system. The initialization of the learning procedure of the network is performed by using the influence coefficient method and the adaptive balancing strategy is prone to converge rapidly to a satisfactory solution. The methodology is tested successfully experimentally.

• Journal of information and communication convergence engineering
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• 제12권2호
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• pp.75-82
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• 2014

Dispersion management (DM), optical phase conjugation (OPC), and the combination of DM and OPC are promising techniques to compensate for optical signal distortion due to group velocity dispersion and nonlinear Kerr effects. The system performance improvement in DM links combined with OPC has been reported; however, the fixed residual dispersion per span (RDPS) usually used in these links restricts the flexibility of link configuration. Thus, in this paper, a flexible optical link configuration with artificially distributed single-mode fiber (SMF) lengths and RDPS in the combination of DM and OPC is proposed. Simulation results show that the best artificial distribution pattern is the gradually descending distribution of SMF lengths and the gradually ascending distribution of RDPS, as the number of fiber spans is increased, regardless of the average RDPS, the optimal net residual dispersion, and the dispersion coefficient of the dispersion compensating fiber.

• Transactions on Electrical and Electronic Materials
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• 제11권3호
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• pp.130-133
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• 2010

A flexible three-axial tactile sensor was fabricated on Kapton polyimide film using polymer micromachining technology. Nichrome (Ni:Cr = 8:2) strain gauges were positioned on an etched membrane to detect normal and shear loads. The optimal positions of strain gauges were determined through strain distribution from finite element analysis. The sensor was evaluated by applying normal and shear loads from 0 N to 0.8 N using an evaluation system. Sensitivity of the tactile sensor to normal and shear loads was about 206.6 mV/N and 70.1 mV/N, respectively. The sensor showed good linearity, and its determination coefficient ($R^2$) was about 0.982. The developed sensor can be applied in a curved or compliant surface that requires slip detection and flexibility, such as a robotic fingertip.

• 대한기계학회논문집
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• 제14권2호
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• pp.288-297
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• 1990

The method of analyzing flexible mechanisms with clearances was studied considering flexibility of beams in the mechanism using finite elements. Both ends of a beam were modeled as free following Dubowsky's impact pair model. Instead some force constraints were imposed at imposed at the connections between adjoining links. Coulomb model has been developed using dry frictions in place of tangential damping forces in the impact pair model and the contact compliance and damping coefficient approximated in a form of root function were used. As examples, impacts of a rigid ball in a cylinder, impact beam model and four-bar mechanisms made up of three flexible links with clearance connections were simulated numerically. The results from examples showed similar but a little bit smaller magnitude of impact forces compared with published studies.

• 한국해양공학회지
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• 제10권1호
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• pp.108-118
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• 1996

This paper presents automatic reentry of a deepsea reser by adaptive control. Reentry is one of the major pro blems regarding a deepsea riser. In the reentry operation, the lower end of riser must be accurately positioned over the tarket point on the seabed. But the deepsea riser shows complex elastic response due to flexibility and nonlinearity of the riser dynamics and the required positioning accuracy is high. Moreover, elastic deformation must by controlled for securing structural integrity. In adaptive control, uncertainly known parameters like added mass and drag coefficient in the riser dynamics are identified and control forces at the floating body and the riser are calculated simultaneously. An Adaptive algorithm for MIMO linear discrete time system without requiring a persistent excitation is adopted in this study. The effectiveness of adaptive control logic is tested by numerical simulation and model experiment. The designed control system shows good overall performances, so that the present study can be applied to the control of the deepsea riser.