• Journal of the Korean Magnetics Society
• /
• v.16 no.1
• /
• pp.34-39
• /
• 2006

Pure and Fe-doped CuO thin-film and powder samples were prepared using a sol-gel method. Undoped CuO films exhibited monoclinic structure and p-type electrical conductivity $(\~10^{-2}\;{\Omega^{-1}\;cm^{-1}$ due to copper deficiency. On the other hand, CuO: Fe films were found to be insulating and Li doping on the films led to a restoration of p-type conductivity and a ferromagnetic hysteresis behaviour at room temperature. The observed properties far the CuO : Fe, Li films can be explained in terms of hole creation by substitution of $Li^+$ for $Cu^{2+}$ sites and mediation of long-range interactions between $Fe^{3+}$ ions by the $Li^+$-induced defect states. CuO: Fe powders exhibited a ferromagnetism at room temperature with its strength being dependent on post-annealing temperature. Mossbauer measurements on the CuO: Fe films and powders revealed that the octahedral $Cu^{2+}$ sites are mostly substituted by $Fe^{3+}$ ions.

• Journal of the Korean Magnetics Society
• /
• v.16 no.4
• /
• pp.211-215
• /
• 2006

Measurement methods in order to measure the mechanical properties nondestructively have been studied. The mechanical properties of the structural and turbine rotor steels are related with their magnetic properties. If the magnetic properties of the cold rolled carbon steel sheet (CR) for a car are measured nondestructively, its mechanical properties are analogized by their magnetic properties. And then the mechanical properties are monitored on-line by measuring the magnetic properties. We prepared three CR materials, CBQ 3060, CBQ 3041, and CBQ 3036, were prepared in order to measure their mechanical and magnetic properties. The Vickers hardness,yield strength, and tensile strength were measured by ASTM E 8M, and the reversible magnetic permeability was measured by the surface type probe. The coercivity calculated by the peak interval of reversible magnetic permeability increased linearly with the increase of Vickers hardness, yield strength, and tensile strength. The amplitude of the peak interval of reversible magnetic permeability drastically decreased when the lift-off was increased.

• Journal of the Korean Wood Science and Technology
• /
• v.37 no.3
• /
• pp.208-215
• /
• 2009

As a fundamental study to develop absorbing materials on harmful volatile organic compounds (VOC) such as formaldehyde, structural and crystalline characteristics of MDF carbonized at different temperatures were examined by a scanning electron microscope and an X-ray diffraction method. Fibers in surface layer of MDFs showed more compressed morphology than those in middle layer of MDFs, but the porosity of MDFs increased with increasing the carbonized temperature. The wrinkle shape was frequently surfaces of cell walls was more severe than that at the lumina of cells. The shape of pits in the fibers of carbonized MDFs were hardly changed. The cell walls of MDFs carbonized at $400^{\circ}C$ and over showed an amorphous-like structure without cell layering. X-ray diffratograms from the MDFs carbonized at $400^{\circ}C$ showed a trace of crystalline cellulose. On the other hand, an amorphous diffraction pattern from carbons was obtained with the MDFs carbonized at $1,000^{\circ}C$.

• Korean Journal of Construction Engineering and Management
• /
• v.14 no.5
• /
• pp.35-43
• /
• 2013

Nowadays the widely used media in architecture include visualizations, animations and three-dimensional models. 3D digital methods using active CAM(Computer Aided Manufacturing) and CNC(Computerized Numerical Control) imaging have been developed for accurate shape and 3D measurements in freeform buildings. In contrast to a conventional building using auto CAD system and others, the proposed digital optimization method is based on a combination of 3D numerical data and parametric 3D model for design and construction. The objective of this paper is therefore to present digital optimization process for constructability of freeform building. The method can be useful in the effective implementation of an error-proofing process of freeform building during design and construction phase. 3D digital coordinate data can be used effectively to identify correct size of structural and finish members and installation location of each members in construction field. In addition, architects, engineers and contractors can evaluate design, materials, constructability and identify error-proofing opportunities. Other project participants can also include representatives from all levels of management, departments as well as workers and key subcontractors' personnel, if necessary. The 3D digital optimization process is therefore appropriate to serious variations in freeform shape. For future study, the developed digital optimization method is necessary to be carried out to verify the robustness and accuracy for constructability in construction field.

• Journal of Conservation Science
• /
• v.26 no.4
• /
• pp.445-458
• /
• 2010

The deterioration and structural damage such as exfoliation, cracks, and separation of painted layer on the wall paintings of Maitreya Hall in Geumsan-sa temple have been accelerated since it was re-positioned to the original place after the dismantling from the building in 1993. The examination of which result and analysis described in this study, is a preliminary survey for establishing conservation plan of the wall paintings. It aimed at the understanding of the physical and chemical characteristics of the materials applied in the 1993 conservation. The research focused on the south walls which displayed the worst condition compared to other walls. Samples for the examination for the understanding of micro-structure, chemical composition, cristalisation, and particle distribution, were collected for finishing, middle, and consolidated layers of the walls between pillars and the ones between brackets. Those samples were collected from separated fragments of the walls. The sample analysis displayed that: 1. the 1993 conservation used the similar type of weathered soil as the original for the finishing layer, and such soil and sand for the middle layer; 2. those walls are composed of a group of mineral particles which are relatively equal in size and shape and in their distribution; 3. the mineral particles were cohered forming solid aggregate due to the application of acrylic resin for the reinforcement on the wall. The main composition of crystalisation on the first and the second reinforcement layers of the back walls were lime plaster ($CaSO_4{\cdot}2H_2O$). The overall examination confirmed that the priority of the future conservation treatment should be given to the removal of the first and the second layers of reinforcement and the treatment on the back walls which were partially consolidated.

• Journal of Microbiology and Biotechnology
• /
• v.26 no.11
• /
• pp.1951-1964
• /
• 2016

1,4-Dioxane-degrading bacterial consortia were enriched from forest soil (FS) and activated sludge (AS) using a defined medium containing 1,4-dioxane as the sole carbon source. These two enrichments cultures appeared to have inducible tetrahydrofuran/dioxane and propane degradation enzymes. According to qPCR results on the 16S rRNA and soluble di-iron monooxygenase genes, the relative abundances of 1,4-dioxane-degrading bacteria to total bacteria in FS and AS were 29.4% and 57.8%, respectively. For FS, the cell growth yields (Y), maximum specific degradation rate ($V_{max}$), and half-saturation concentration ($K_m$) were 0.58 mg-protein/mg-dioxane, $0.037mg-dioxane/mg-protein{\cdot}h$, and 93.9 mg/l, respectively. For AS, Y, $V_{max}$, and $K_m$ were 0.34 mg-protein/mg-dioxane, $0.078mg-dioxane/mg-protein{\cdot}h$, and 181.3 mg/l, respectively. These kinetics data of FS and AS were similar to previously reported values. Based on bacterial community analysis on 16S rRNA gene sequences of the two enrichment cultures, the FS consortium was identified to contain 38.3% of Mycobacterium and 10.6% of Afipia, similar to previously reported literature. Meanwhile, 49.5% of the AS consortium belonged to the candidate division TM7, which has never been reported to be involved in 1,4-dioxane biodegradation. However, recent studies suggested that TM7 bacteria were associated with degradation of non-biodegradable and hazardous materials. Therefore, our results showed that previously unknown 1,4-dioxane-degrading bacteria might play an important role in enriched AS. Although the metabolic capability and ecophysiological significance of the predominant TM7 bacteria in AS enrichment culture remain unclear, our data reveal hidden characteristics of the TM7 phylum and provide a perspective for studying this previously uncultured phylotype.

• Composites Research
• /
• v.28 no.4
• /
• pp.155-161
• /
• 2015

A composite structure was fabricated with embedded impact detection capabilities for applications in Structural Health Monitoring (SHM). By embedding sensor functionality in the composite, the structure can successfully perform impact localization in real time. Smart resin, composed of $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,\;Ti)O_2$ (PNN-PZT) powder and epoxy resin with 1:30 wt%, was used instead of conventional epoxy resin in order to activate the sensor function in the composite structure. The embedded impact sensor in the composite was fabricated using Hand Lay-up and Vacuum Assisted Resin Transfer Molding(VARTM) methods to inject the smart resin into the glass-fiber fabric. The electrodes were fabricated using silver paste on both the upper and bottom sides of the specimen, then poling treatment was conducted to activate the sensor function using a high voltage amplifier at 4 kV/mm for 30 min at room temperature. The composite's piezoelectric sensitivity was measured to be 35.13 mV/N by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. Because impact sensor functionality was successfully embedded in the composite structure, various applications of this technique in the SHM industry are anticipated. In particular, impact localization on large-scale composite structures with complex geometries is feasible using this composite embedded impact sensor.

• Composites Research
• /
• v.28 no.6
• /
• pp.356-360
• /
• 2015

In this paper, the carbon fiber reinforced plastic is processed as the double cantilever beam in order to estimate the fracture behavior of composite and is carried out with the static analysis as the mode I. The specimen sizes are 25 mm, 30 mm, 35 mm and 40 mm. And the material property is used with carbon. As the analysis result of mode I, the adhesive part is detached latest by the small force at the specimen thickness of 25 mm. The largest force is happened at the specimen thickness of 40 mm. The defection of the adhesive interface is shown slowest at the displacement of 9.75 mm at the specimen thickness of 25 mm. And the defection is shown quickest at the displacement of 7.82 mm at the specimen thickness of 40 mm. This defection is due to the fracture of specimen. The result of this study on the defection of the adhesive interface and the reaction force due to this defection is thought to be contributed to the safe structural design of the carbon fiber reinforced plastic.

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.993-1000
• /
• 2005

Various types of FRP materials have been applied for structural strengthening of RC beams in various forms. When CFRP plates are used, a premature failure used to occur before enough strengthening effect appears. This is primarily due to the rip-off of CFRP Plate attached on RC beams. Despite of numerous studies on the rip-off failure of externally strengthened RC beams, its failure mechanism is not definitely clarified yet. Investigations from literatures have shown that the rip-off failure is dependant on the vertical and shear stresses at the level of main reinforcements in RC beams. This study suggests an analytical model to Investigate the rip-off failure load based on the stress states at the level of main reinforcements. The proposed model is relatively simple and produces very comparable results to the test data. It is believed that the proposed model can be successfully used to provide more information on the rip-off failure mechanisms and its prevention.

• Journal of the Korea Concrete Institute
• /
• v.23 no.3
• /
• pp.377-384
• /
• 2011

Although concrete is considered as fire proof materials, high strength concrete shows severe material and structural damages when exposed to fire. To understand such damages in high strength concrete structures, the effects of various design parameters and fire condition on the thermal behaviors of high strength concrete structures are investigated in this study. In order to achieve this goal, fire tests are performed on high strength concrete columns with different fire conditions and design parameters including cross sectional area, cover thickness, and reinforcement alignment. To investigate thermal behaviors, temperature distributions and amount of spalling are measured. In overall, the columns show rapidly increasing inner temperatures between 30~60 mins of the fire tests due to spalling. In detail, the higher temperature distributions are observed from the columns with the larger cross section and less cover thickness. Moreover, among the columns with same reinforcing ratio, larger number of reinforcements with the smaller diameter causes the higher temperature distribution. The findings from the experimental study allow not only understanding of thermal behaviors of high strength concrete columns under fire, but also guidance in revising fire safety design.