• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.158-163
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• 2009

Many longitudinal pipes in ships are subject to considerable loads, caused by hull girder bending in the ships and/or thermal loads in some special pipes through which fluids with highly abnormal temperatures are conveyed. As these loads may cause failure in the pipes or their supporting structures, loops have been widely adopted to prevent such failure, based on the idea that they can lower the stress level in a pipe byabsorbing some portion of these loads. But as the loops also have some negative effects, such as causing extra manufacturing cost, deteriorating the function of the pipe, and occupying extra space, the number and dimensions of these loops need to be minimized. This research developed design formulas for pipe loops, modeling them as a spring element, for which the axial stiffness is calculated based on the beam theory, incorporating the flexibility effect of the straight portion of the pipe. The accuracy of the proposed design formulas was verified by comparing two results obtained from the proposed formulas and MSC/NASTRAN. This paper concludes with a sample application of the proposed formulas, showing their efficiency.

• Steel and Composite Structures
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• v.22 no.4
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• pp.889-913
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• 2016

Vibration analysis of embedded functionally graded (FG)-carbon nanotubes (CNT)-reinforced piezoelectric cylindrical shell subjected to uniform and non-uniform temperature distributions are presented. The structure is subjected to an applied voltage in thickness direction which operates in control of vibration behavior of system. The CNT reinforcement is either uniformly distributed or functionally graded (FG) along the thickness direction indicated with FGV, FGO and FGX. Effective properties of nano-composite structure are estimated through Mixture low. The surrounding elastic foundation is simulated with spring and shear constants. The material properties of shell and elastic medium constants are assumed temperature-dependent. The motion equations are derived using Hamilton's principle applying first order shear deformation theory (FSDT). Based on differential cubature (DC) method, the frequency of nano-composite structure is obtained for different boundary conditions. A detailed parametric study is conducted to elucidate the influences of external applied voltage, elastic medium type, temperature distribution type, boundary conditions, volume percent and distribution type of CNT are shown on the frequency of system. In addition, the mode shapes of shell for the first and second modes are presented for different boundary conditions. Numerical results indicate that applying negative voltage yields to higher frequency. In addition, FGX distribution of CNT is better than other considered cases.

• Steel and Composite Structures
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• v.37 no.1
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• pp.99-115
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• 2020

This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO₂) subject to seismic load. In order to control the foundation smartly, a piezoelectric layer covered the foundation. The weight of the building by a column on the foundation is assumed with an external force in the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori-Tanaka law is utilized for calculating the equivalent mechanical characteristics of the concrete foundation. The Kevin-Voigt model is adopted to take into account the structural damping. The concrete structure is modeled by a thick plate and the governing equations are deduced using Hamilton's principle under the assumption of higher-order shear deformation theory (HSDT). The differential quadrature method (DQM) and the Newmark method are applied to obtain the seismic response. The effects of the applied voltage to the smart layer, agglomeration and volume percent of SiO₂ nanoparticles, damping of the structure, geometrical parameters and soil medium of the structure are assessed on the dynamic response. It has been demonstrated by the numerical results that by applying a negative voltage, the dynamic deflection is reduced significantly. Moreover, silica nanoparticles reduce the dynamic deflection of the concrete foundation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.338-343
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• 2018

Recently, commercial catches of the common squid Todarodes pacificus have dramatically decreased in Korean and Japanese waters. The relationship between common squid catches and environmental factors was investigated using squid catches, climate indices and observed seawater temperatures in Korean waters. Common squid consist of three spawning stocks: autumn, winter, and summer. The autumn stock is the largest in Korea, and its main fishing season appears to have shifted from September in the 1980s to October in the 1990s. We observed negative correlations between the spring Southern Oscillation Index and Korean catches and between the winter Pacific Decadal Oscillation and Japanese catches. Despite global warming, no conspicuous increases in October seawater temperatures have been observed at 10 and 50 m in Korean waters since the mid-1900s. Instead, the 50 m water layer of the East Sea appears to be gradually cooling. Moreover, temperatures at 50 m in the East Sea and the South Sea were significantly negatively correlated with squid catches in Korea and Japan, respectively. Our preliminary analysis indicates a link between climate change, seawater temperature, and squid catches in Korean waters, which helps to inform the direction of subsequent research to identify the cause of rapid decreases in this squid resource.

• Journal of The Korean Society of Grassland and Forage Science
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• v.14 no.2
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• pp.93-98
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• 1994

This experiment was canied out to investigated the effect of slope exposure on winter hardiness of grasses in mountainous pastures of Taekwalyong area The results obtained were summarized as follows; 1. Plant vigour(PV) before wintering influenced on the growth of next spring, field survival rates and winter hardiness of grasses. 2. The dry weight of plant per relative tiller appearance rates(DW/RTAR) was significantly negative correlated with plant vigour(PV) before wintering, but the weight of plant per relative tiller appearance rates(DW1 RTAR) were significantly positive correlated with the number of tiller per plant before wintering($NT_O$), number of tillers per plant of 1st cutting(NT), dry weight of plant(DW), field survival rates(SR) and relative tiller appearance rate(RTAR). 3. There ranking order of high winter hardiness of grasses, it were west(W), north-north west(NNW), eastsoutheast( ESE) and south-southwest(SSW) exposure, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.2
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• pp.140-148
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• 2000

In this paper, using surface micromachining technology with thick photoresist and aluminum, an SLM(Spatial Light Modulator), which is applied to the fields of adaptive optics and pattern recognition system, was fabricated and the electromechanical properties of the fabricated micro SLM are measured. In order to maximize fill-factor and remove mechanical coupling between micro SLM actuators, the micro SLM is composed of three aluminum layers so that spring structure and upper electrode are placed beneath the mirror plate, and $10\times10$ each mirror plate is individually actuated. Also, the micro SLM was designed to be able to modulate phase and amplitude of incoming light in order to have a continuity of phase modulation of incoming light. In the case of amplitude and phase modulation, maximum vertical displacement is 4$\mum$, and maximum angular displacement is $\pm4.6^{\corc}$ respectively. The height difference of the fabricated mirror plate was able to be reduced to 1100A with mirror plate planarization method using negative photoresist(AZ5214). The electromechanical properties of the fabricated micro SLM were measured with the optical measurement system using He-Ne laser and PSD(position sensitive device).

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2005.11a
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• pp.249-254
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• 2005

The purpose of this study is to provide the guideline of the outdoor space of residential land development district for children's outdoor activites. This study was accomplished by the valuation of the physical environment of 5 residential land development districts, the analyzation of behavioral mapping about children's outdoor activities, and the analyzation of satisfaction and the consciousness of 190 residents(parents) & 230 children. Especially, outdoor spaces were divided into 6 parts (play space, education facility, commercial facility, green space, and empty space & parking lot). And than, 6 outdoor spaces were valuated about the physical characters such as accessibility, network, safety, variety, functional, natural elements. Also, the survey for residents and children's consciousness were used the Likert scale. According to the result of this study, many parts of the housing area were not good for children's activities, and resident's satisfaction was low. In the sample areas, negative factors were car and motorcycle. And many residents were pointed out the lack of natural elements, variety, and safety of outdoor space in dwelling area. Finally, this study suggested the guideline children's activities based on the result of analyzation of valuation, behavioral mapping, and survey.

• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.87-93
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• 2012

Many longitudinally-arranged pipes in ships are equipped with loops as a measure to reduce stresses caused by displacement loads conveyed from the hull girder bending and/or thermal loads of carried fluid of non-ambient temperature. But as the loops have some negative effects such as causing extra manufacturing cost and occupying extra space, the number and the dimensions of the loops need to be minimized. In the meanwhile, a design formula for pipe loops has been developed by modeling them as a spring element of which stresses and axial stiffness are calculated based on the beam theory. But as the beam theory turns out to be inappropriate to deal with the complex structural behavior in the curved corner portion of the loop, this paper aims at improving the previously developed design formula by adopting correction factors which can allow for the gap between the results of beam theory and a more accurate analysis. This paper adopts a finite element analysis with two-dimensional shell elements with some validation work for it. The paper ends with a sample application of the proposed formulas showing their accuracy and efficiency.

• Journal of Ocean Engineering and Technology
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• v.23 no.4
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• pp.91-99
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• 2009

Many longitudinally arranged pipes in ships are subject to considerable displacement loads caused by the hull girder bending of ships and/or thermal loads in some special pipes through which fluids with highly abnormal temperatures are conveyed. As these loads may cause failure in the pipes or their supporting structures, loops have been widely adopted as a measure to prevent such failure, with the idea that they can lower the stress level in a pipe by absorbing some portion of these loads. But since such loops have some negative effects, such as causing extra manufacturing cost and occupying extra space, the number and dimensions of the loops need to be minimized. This research developed design formulas for pipe loops, modeling them as a spring element, for which the axial stiffness is calculated based on the beam theory, incorporating the effects of the curvature of loop corners and the flexibility of the straight portion of the pipe. The accuracy of the proposed design formulas was verified by comparing two results respectively obtained by the proposed formulas and MSC/NASTRAN. The paper ends with a sample application of the proposed formulas showing their efficiency.