• Smart Structures and Systems
• /
• v.7 no.5
• /
• pp.417-432
• /
• 2011

The present paper is devoted to vibration canceling and shape control of piezoelastic slender beams. Taking into account the presence of electric networks, an extended electromechanically coupled Bernoulli-Euler beam theory for passive piezoelectric composite structures is shortly introduced in the first part of our contribution. The second part of the paper deals with the concept of passive shape control of beams using shaped piezoelectric layers and tuned inductive networks. It is shown that an impedance matching and a shaping condition must be fulfilled in order to perfectly cancel vibrations due to an arbitrary harmonic load for a specific frequency. As a main result of the present paper, the correctness of the theory of passive shape control is demonstrated for a harmonically excited piezoelelastic cantilever by a finite element calculation based on one-dimensional Bernoulli-Euler beam elements, as well as by the commercial finite element code of ANSYS using three-dimensional solid elements. Finally, an outlook for the practical importance of the passive shape control concept is given: It is shown that harmonic vibrations of a beam with properly shaped layers according to the presented passive shape control theory, which are attached to an resistor-inductive circuit (RL-circuit), can be significantly reduced over a large frequency range compared to a beam with uniformly distributed piezoelectric layers.

• Smart Structures and Systems
• /
• v.5 no.6
• /
• pp.613-632
• /
• 2009

The present paper is concerned with the design of a proper patch actuator network in order to track a desired displacement of the sidewalls of a one-storey frame structure; both, for the static and the dynamic case. Weights for each patch of the actuator network found in our previous work were based on beam theory; in the present paper a refinement of these weights by modeling the sidewalls of the frame structure as thin plates is presented. For the sake of calculating the refined weights approximate solutions of the plate equations are calculated by an extended Galerkin method. The solutions based on the analytical plate model are compared with three-dimensional Finite Element results computed in the commercially available code ANSYS. The patch actuator network is put into practice by means of four piezoelectric patches attached to each of the two sidewalls of the frame structures, to which electric voltages proportional to the analytically refined patch weights are applied. Analytical and numerical results coincide very well over a broad frequency range.

• Steel and Composite Structures
• /
• v.29 no.6
• /
• pp.749-758
• /
• 2018

This article derived a hybrid coupling technique using the higher-order displacement polynomial and three soft computing techniques (teaching learning-based optimization, particle swarm optimization, and artificial bee colony) to predict the optimal stacking sequence of the layered structure and the corresponding frequency values. The higher-order displacement kinematics is adopted for the mathematical model derivation considering the necessary stress and stain continuity and the elimination of shear correction factor. A nine noded isoparametric Lagrangian element (eighty-one degrees of freedom at each node) is engaged for the discretisation and the desired model equation derived via the classical Hamilton's principle. Subsequently, three soft computing techniques are employed to predict the maximum natural frequency values corresponding to their optimum layer sequences via a suitable home-made computer code. The finite element convergence rate including the optimal solution stability is established through the iterative solutions. Further, the predicted optimal stacking sequence including the accuracy of the frequency values are verified with adequate comparison studies. Lastly, the derived hybrid models are explored further to by solving different numerical examples for the combined structural parameters (length to width ratio, length to thickness ratio and orthotropicity on frequency and layer-sequence) and the implicit behavior discuss in details.

• Earthquakes and Structures
• /
• v.19 no.6
• /
• pp.471-484
• /
• 2020

Previous earthquakes show that, structural safety evaluations should include the evaluation of nonstructural components. Failure of nonstructural components can affect the operational capacity of critical facilities, such as hospitals and fire stations, which can cause an increase in number of deaths. Additionally, failure of nonstructural components may result in economic, architectural, and historical losses of community. Accelerations and random vibrations must be under the predefined limitations in structures with high technological equipment, data centers in this case. Failure of server equipment and anchored server racks are investigated in this study. A probabilistic study is completed for a low-rise rigid sample structure. The structure is investigated in two versions, (i) conventional fixed-based structure and (ii) with a base isolation system. Seismic hazard assessment is completed for the selected site. Monte Carlo simulations are generated with selected parameters. Uncertainties in both structural parameters and mechanical properties of isolation system are included in simulations. Anchorage failure and vibration failures are investigated. Different methods to generate fragility curves are used. The site-specific annual hazard curve is used to generate risk curves for two different structures. A risk matrix is proposed for the design of data centers. Results show that base isolation systems reduce the failure probability significantly in higher floors. It was also understood that, base isolation systems are highly sensitive to earthquake characteristics rather than variability in structural and mechanical properties, in terms of accelerations. Another outcome is that code-provided anchorage failure limitations are more vulnerable than the random vibration failure limitations of server equipment.

• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.238-247
• /
• 2023

The present work represents a technical guideline for decommissioning a disused teletherapy machine model Theratron-780 and contains category one ⁶⁰Co radioactive source. The first section predicts the dose rate from the source in case of normal and radiological emergency situations via FLUKA-MC simulation code. Moreover, the dose assessment for the occupational during the whole process is calculated and compared to the measured values. A suggested cordoned area for safety and security in a radiological emergency is simulated. The second section lists the whole process's technical procedures, including (preview, dismantle, securing, transport and storage) of the disused teletherapy machine. Results show that the maximum obtained accumulated dose for occupational were found to be 24.5 ± 4.9 μSv in the dismantle and securing process in addition to 3.5 ± 1.8 μSv during loading on the transport vehicle and unloading at the storage facility. It was found that the measured accumulated dose for workers is in good agreement with the estimated one by uncertainty not exceeding 5% in normal operating conditions.

• 전자공학회논문지 IE
• /
• v.43 no.4
• /
• pp.115-121
• /
• 2006

In this paper, we proposed about data error check and correction on channel transmission in the communication system. LDPC codes are used for minimizing channel errors by modeling AWGN Channel as a VDSL system. Because LDPC Codes use low density parity bit, mathematical complexity is low and relating processing time becomes shorten. Also the performance of LDPC code is better than that of turbo code in long code word on iterative decoding algorithm. This algorithm is better than conventional algorithms to correct errors, the proposed algorithm assigns weights for errors concerning parity bits. The proposed weighted Bit-flipping algorithm is better than the conventional Bit-flipping algorithm and we are recognized improve gain rate of 1 dB.

• International Commerce and Information Review
• /
• v.8 no.3
• /
• pp.299-321
• /
• 2006

The purpose of this study was to analyze export competitiveness of Korean auto parts and Chinese auto parts in U.S. market by using Index of Export Bias and Market Comparative Advantage Index. For attaining the purpose of study, we classified the auto parts which exported to U.S. market and the imported products by using the six units classification of the Harmonized System(HS). Analyzing period was 1998-2005. The analysis of Korean results of MCA indicated that the Korean auto parts which gained export competitiveness in the U.S. market were HS Code No. 8708.94, 8708.99, 8708.92. The products which will have export competitiveness in the U.S. market would be HS Code No. 8708.93, 8708.39, 8708.60 respectively. On the other hand, the results indicated that the Chinese auto parts which gained export competitiveness in the U.S. market were HS Code No. 8708.70, 8708.31, 8708.91, 8708.60, 8708.39. From this study, we find the following strategies for successful advancing into the U.S. and world market. i) Linking strategy through working cooperation with local auto firms, government and academic world. ii) Advance strategy of auto firm accompany by module working and system auto parts firm. iii) Retention strategy of large technical institution established by auto parts firms and taking cooperation of auto firms iv) Settlement strategy for having weaken competitive article and production field. v) Cost-cutting strategy through strengthening logistics cooperation system between auto parts firms and auto firms. vi) Active invitation strategy of foreign investment under quickly cooperating of government.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.39 no.2
• /
• pp.233-246
• /
• 2015

Focus on Digital Fashion Image, the conceptual framework for the thesis is established from Virtuality in Digital Art. Formative characteristics and aesthetic characteristics were studied by classifying the Digital Fashion Image applied and expressed by digital media and technology. A detective research method was used for a case study. A literature study for case-by-case data was analyzed with focus on the works expressing fashion that utilized digital media and technology since the 2000s. Through this study, the Digital revolution has created the socio-cultural impact of a Virtual representation to implement technology and fashion culture that finds ways to take advantage of the image shown in a Digital Fashion Media by understanding Virtuality. The results are as follows. First, it was a re-formation of the fashion culture through the experience of virtuality with mental zone parameters between the media 'Mediation Code'. Reflect the reality of the virtual environment as represented by a cultural image of fashion brands and fashion that reset the team relationship and formed a Homo Ludens cultural code. Second, 'Interactive Exchange' acts on the exchange interaction between the method of digital technology, the human and the machine as well as the technical interoperability of network elements and techniques. This exchange is applied to fashion images that express emotion. Forming personalized fashion items and the user interactively storage that expresses the interactive exchange to forward the identity of the emotional fashion by a change in the message delivery system fashion. Third, the emphasis on intuitive artistic expression 'Synesthesia Immersion' induces a sense of immersion and excitement through the fusion of the interconnected. Enhance a visual image in fashion sensory representation and maximize a tactile and visual virtual reality involvement.

• Structural Engineering and Mechanics
• /
• v.66 no.2
• /
• pp.203-215
• /
• 2018

A large body of experiments have been conducted to date to evaluate the punching shear strength of flat slab-column connections, but it is noted that only a few of them have been considered for the development of the ACI Code provisions. The limited test results used for the development of the code provisions fall short of predicting accurately the punching shear strength of such connections. In an effort to address this shortfall and to gain an insight into the factors that control the punching shear strength of flat slab-column connections, we report a qualified database of 650 punching shear test results in this article. All slabs examined in this database were tested under gravity loading and do not contain shear reinforcement. In order to justify including any test result for evaluation punching shear database, we have developed an approved set of criteria. Carefully established set of criteria represent the actual characteristics of structures that include minimum compressive strength, effective depths of slab, flexural and compression reinforcement ratio and column size. The key parameters that significantly affect the punching shear strength of flat slab-column connections are then examined using ACI 318-14 expression. The results reported here have paramount significance on the range of applicability of the ACI Code provision and seem to indicate that the ACI provisions do not sufficiently capture many trends identified through regression of the principal parameters, and fall on the unsafe side for the prediction of the punching shear strength of flat slab-column connections.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.5
• /
• pp.579-585
• /
• 2014

For the application of fuel cell systems on ship which is future eco-friendly ship technology, it is need that the modification of relevant laws and regulations with relevant technical development. This paper reviews the trend of fuel cell development, SOLAS and IACS UR/UI as a international regulations, international standardization trend such as IMO MEPC, IMO BLG and major classification rules, the consideration for the standard development of ship fuel cell systems, the implications for application of fuel cell systems on ships in Korea. The IGF Code which is developing in the IMO included fuel cell, and thus Korean government and related company should participate in the codification. The analysis of development of IMO's relevant regulations also needed for the preparations.