• 한국지진공학회논문집
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• 제21권1호
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• pp.59-67
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• 2017

Due to a lack of the hoop action of lateral reinforcements the effective confining force in rectangular sections reduces compared to circular ones. Therefore, the stress-strain model obtained from the experimental data with circular sections overestimates the lateral confinement effect in rectangular sections, which evaluates seismic safety margin of overall structural system excessively. In this study experiments with laterally-confined square sections have been performed and the characteristic values composing stress-strain model have been analyzed. With introduction of section coefficients, in addition, the new unified stress-strain model applicable to square sections as well as circular ones has been proposed.

• 한국소음진동공학회논문집
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• 제19권9호
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• pp.915-921
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• 2009

Cellulose based electro-active paper(EAPap) is considered as a new smart material which has a potential to be used for biomimetic actuators and sensors. Beside of the natural abundance, cellulose EAPap is fascinating with its biodegradability, lightweight, high mechanical strength and low actuation voltage. When the external stress is applied to EAPap, it can generate the electrical output due to its piezoelectric property. Using piezoelectric behavior of EAPap, we studied the feasibility of EAPap as mechanical strain sensor applications and compared to commercial strain sensor. By measuring the induced output voltage from the thin piezoelectric cellulose EAPap under static and dynamic force, we propose cellulose EAPap film as a potential strain sensor material.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.269-272
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• 1999

It is still hard to measure the strain distribution over entire surface of a medium or large-size stamped part even by using an automated strain measurement system. Several methods which enable to enlarge the measurement range without losing accuracy and precision are suggested in this study, The superposition of images having different high-lightened or damaged part each other results in an enhanced image. A new method for constructing the element connectivity from a line-thinned image makes it possible to identify up to 1,000 elements. And the geometry assembling algorithm is proved very efficient in which the whole area to be measured is divided into several parts ; the coordinate transformation between every two adjacent parts is obtained from the concept of the least square error ; and the 3-D shape or strain distribution over the whole surface is assembled,

• 한국항해학회지
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• 제21권3호
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• pp.49-54
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• 1997

It is very important to measure and monitor hull stress which is caused by a buoyant force and a weight of cargo for safety of ship. However, an exact measurement of hul stress, using the traditional strain gage which is made of metal or semiconductor, is very difficult, because a ship would be exposed by the severe temperature environment of $-20 ^{\circ}C$ to $80 ^{\circ}C$. This paper propose a new concept strain gage which can improve accuracy and compensage effectively affects due to temperature. The strain gage is consists of two parts. One is the Hull Deformation Amplifier which introuce several lever and link system, and another is a transducer converting distance into voltage signal. The HDA measure the amount of deformation and amplify it. And a lever and link system of the HDA is introduced for compensating temperature deformation by installing in perpendicular direction without stress. This paper also reports on the results of the experiments to verify linearity of the strain gage.

• Journal of Applied Biological Chemistry
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• 제43권2호
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• pp.74-78
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• 2000

A strain that produces a high level of carboxymethyl cellulase was isolated from rotten leaves. The isolated strain was revealed to be gram-negative, oxidase-positive, and catalase-negative. From the electron microscopic features, it was identified as a rod-shaped bacterium with peritrichous flagella and did not form spores. Morphological and biochemical characteristics of the strain were found to be similar to the Pseudomonas species. However, carbon utilization test showed different results. Based on the results, this new strain was identified as Pseudomonas sp. CMC-50. CMCase produced by this strain showed a strong activity in neutral and weak acidic conditions and maximum activity at $50^{\circ}C$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.132-137
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• 2004

In this work, effects of hyper-elastic rubber material properties on the indentation load-deflection curve and subindenter deformation are first examined via [mite element (FE) analyses. An optimal data acquisition spot is selected, which features maximum strain energy density and negligible frictional effect. We then contrive two normalized functions. which map an indentation load vs. deflection curve into a strain energy density vs. first invariant curve. From the strain energy density vs. first invariant curve, we can extract the rubber material properties. This new spherical indentation approach produces the rubber material properties in a manner more effective than the common uniaxial tensile/compression tests. The indentation approach successfully measures the rubber material properties and the corresponding nominal stress.strain curve with an average error less than 3%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1529-1531
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• 2003

Thick film mechanical sensors can be categorized into four main areas piezoresistive, piezoelectric, piezocapastive and mechanic tube. In this areas, the thick film strain gage is the earliest example of a primary sensing element based on the substrates. The latest thick film sensor is used various pastes that have been specifically developed for pressure sensor application. The screen printing technique has been used to fabricate the pressure sensors on alumina substrate($Al_2O_3$). Thick film capacitive of strain sensing characteristics are reported and dielectric paste based on (Ti+Ba) materials. The electric property of dielectric paste has been studied and exhibit good properly with good gage factor comparable to piezoresistive strain gage. New piezocapacitive strain sensor was designed and tested. The output of capacitive value was good characteristics.

• Structural Engineering and Mechanics
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• 제77권3호
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• pp.369-381
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• 2021

The seismic responses of elevated tanks considering liquid-structure interaction are presented under horizontal earthquake. The scaled model tank is fabricated to study the dynamic responses of anchored tank and newly designed uplift tank with replaced dampers. The natural frequencies for structural mode are obtained by modal analysis. The dynamic responses of tanks are completed by finite element method, which are compared with the results from experiment. The displacement parallel and perpendicular to the excitation direction are both gained as well as structural acceleration. The strain of tank walls and the axial strain of columns are also obtained afterwards. The seismic responses of liquid storage tank can be calculated by the finite element model effectively and the results match well with the one measured by experiment. The aim is to provide a new type of tank system with vertical constraint relaxed which leads to lower stress level. With the liquid volume increasing, the structural fundamental frequency has a great reduction and the one of uplift tank are even smaller. Compared with anchored tank, the displacement of uplift tank is magnified, the strain for tank walls and columns parallel to excitation direction reduces obviously, while the one perpendicular to earthquake direction increases a lot, but the values are still small. The stress level of new tank seems to be more even due to uplift effect. The new type of tank can realize recoverable function by replacing dampers after earthquake.

• Steel and Composite Structures
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• 제44권6호
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• pp.817-828
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• 2022

In this study, considering dissipated energy in fracture process zone (FPZ), a novel criterion based on maximum strain energy release rate (SER) for orthotropic materials is presented. General case of in-plane loading for cracks along the fibers is assumed. According to the experimental observations, crack propagation is supposed along the fibers and the reinforcement isotropic solid (RIS) concept is employed as a superior model for orthotropic materials. SER in crack initiation and propagation phases is investigated. Elastic properties of FPZ are extracted as a function of undamaged matrix media and micro-crack density. This criterion meaningfully links between dissipated energy due to toughening mechanisms of FPZ and the macroscopic fracture by defining stress intensity factors of the damaged zone. These coefficients are used in equations of maximum SER criterion. The effect of crack initiation angle and the damaged zone is considered simultaneously in this criterion and mode II stress intensity factor is extracted in terms of stress intensity factors of damage zone and crack initiation angle. This criterion can evaluate the effects of FPZ on the fracture behavior of orthotropic material. Good agreement between extracted fracture limit curves (FLC's) and available experimental data proves the ability of the new proposed criterion.

• KSBB Journal
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• 제27권3호
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• pp.151-156
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• 2012

Lactic acid is an important product arising from the anaerobic fermentation by lactic acid bacteria (LAB). It is used in the pharmaceutical, cosmetic, chemical, and food industries as well as for biodegradable polymer and green solvent production. The poly lactic acid (PLA) is an important material for bio-plastic manufacturing process. For PLA production by new LAB, we screened LAB isolates from shellfish. A total of 28 LAB were isolated from various shellfishes. They were all Gram positive, oxidase and catalase negative. Based on API 50CHL kit, 7 strains among the 28 isolates were identified as Lactobacillus plantarum, 6 strains as Lactobacillus delbrueckii, 5 strains as Leuconostoc mesenteroides, 3 strains as Lactobacillus brevis, 2 strains as Lactococcus lactis, 1 strain as Lactobacillus salivarius, 1 strain as Lactobacillus paracasei, 1 strain as Lactobacillus pentosus, 1 strain as Lactobacillus fermentum and 1 strain as Pediococcus pentosaceu. Also, we examined the amount of total lactic acid produced by these new strains by HPLC analysis with Chiralpak MA column. One strain E-3 from Mytilus edulis was indentified as Lactobacillus plantarum and found to produce 20.0 g/L of D-form lactic acid from 20 g/L of dextrose. Further studies are underway to increase the D-lactic acid production by E-3.