• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.689-696
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• 2017

The practical applications of ordinary high-fluidity concrete have been limited due to several drawbacks, such as high hydration heat, high amount of shrinkage, and non-economic strength development. On the other hand, due to its advantages, such as improvement of construction quality, reduction of construction cost and period, the development of high-fluidity concrete is a pressing need. This study examined the properties of high-fluidity concrete, which can be manufactured on the low binders using a viscosity agent to prevent the segregation of materials. The optimal viscosity agent was selected by an evaluation of the mechanical properties of high-fluidity concrete among six viscosity agents. The acrylic type and urethane type viscosity agents showed the best performance within the range where no material separation occurred. The mechanical properties were evaluated to examine the optimal amount of AC and UT viscosity agent added by mixing two viscosity agents according to the adding ratio and blending them together with high performance water reducing agent. When the ratio of the AC : UT viscosity agents was 5:5, it was most suited for high-fluidity concrete with low binders by increasing the workability and effect of the reducing viscosity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.711-717
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• 2017

Measurements of the moment of inertia of a small turbocharger rotor were studied. A measuring device was manufactured using the trifilar method and the moment of inertia of the calibration rotor was measured to verify the device. The coefficient of variation was 0.43% and the error was 0.75%. The results showed that the device is suitable for measuring the moment of inertia of a turbocharger rotor. Next, the moment of inertia for two turbine rotors and compressor wheels was measured. Those for the turbine rotors showed precise and accurate results in that the coefficients were under 1.0% and the errors were under 3.0%. On the other hand, those for the compressor wheel were precise but inaccurate in that the coefficients were under 1.0% and the errors were over 24.4%. Therefore an indirect method for the compressor wheel was suggested. The results showed that the coefficients were under 1.2% and the errors were under 7.88%.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.4
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• pp.251-258
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• 2014

A wheelchair is a typical mobility aid for the physically disabled or the old and the weak, and is the most commonly used rehabilitation aid. In general, most of users of manual wheelchair have difficulty though vocational rehabilitation and independent living is possible. The reason is that long-distance movement is always accompanied with wheelchair transfer problem because a wheelchair is used as direct means of transport. Hence, the wheelchair transfer problem should be first solved in order that a wheelchair user can independently live. Therefore, this study examined and analyzed the domestic and overseas launched products and patented technologies of wheelchair transfer system for vehicle, and proposed a wheelchair transfer mechanism of a new system for vehicle. This study proposed a wheelchair transfer mechanism for vehicle in order to remove the disadvantage of wheelchair transfer system for vehicle to support the conventional wheelchair user's movement, and in order to conform with the structure of domestic welfare vehicle for the disabled. Because a difference between storage space installed in the roof of vehicle and storage space for leisure, which is generally utilized, gets to disappear by applying this proposed mechanism, popularity among users can be increased. And storage space that has become smaller like this will be capable of decreasing the disadvantage of air resistance in traveling. Besides, because of getting to conform with the structure of welfare vehicle, restrictions on the application range will disappear from small sedan to SUV. Therefore, users can have more choices.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.534-540
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• 2006

Thin films of $V_2O_3$, $VO_2$, and $V_2O_5$ were obtained from a single precursor solution through post-annealing processes under different annealing conditions. As annealed in air, the deposited films became $V_2O_5$ with orthorhombic crystal structure, while they were $V_2O_3$ and $VO_2$ with rhombohedral and monoclinic crystal structure as annealed in vacuums with base pressure of $1{\times}10^{-6}$ Torr and with 10 mTorr $O_2$ pressure, respectively. Electrical and optical measurements indicated that the $V_2O_5$ and $VO_2$ films are semiconducting, while the $V_2O_3$ films are metallic at room temperature. Chromium doping in $VO_2$ resulted in a decrease of the resistivity and changed the conduction type from n-type to p-type. 10% Cr-doped $VO_2$ films were found to have orthorhombic crystal structure, which is different from that of the undoped $VO_2$. Spectral features in the optical absorption spectra of all the films were interpreted as the transitions involving O 2p and V 3d bands. The crystal-field splittings between $t_{2g}$ and $e_g$ states of the V 3d bands are estimated to be about 1.5 and 1.0 eV for $V_2O_5$ and $VO_2$, respectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.3
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• pp.211-221
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• 2009

With recent trends of super-tallness, atypical plan shapes and zoning constructions in high-rise buildings, a structural stability of the building under construction is arising as a key issue for design and construction plan. To ensure the structural stability under construction, the differential column shortening of vertical members, the lateral displacement of tower frames, and differential settlement of raft foundation by unbalanced distributions of a tower self-weight before the completion of a lateral load resisting system should be checked by construction sequence analysis, which should be performed by systematic combinations with structural health monitoring, construction compensation program, and construction panning. This paper presents the scheme of zone-based construction sequence analysis by using the existing commercial analysis program, to check the stability of high-rise building under construction. This scheme is applied to 3-dimensional structural analysis for a real high-rise building under construction. The analysis includes real construction zoning plans and schedules as well as creep and shrinkage effects and time-dependent properties of concrete. The simplified construction sequence and assumed material properties were continuously updated with the change on construction schedule and correlations with in-situ measurement data.

• Journal of the Korea Institute of Building Construction
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• v.13 no.6
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• pp.602-608
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• 2013

The aim of this study is to investigate experimentally the effect of the combination of fine particle cement with high Blaine fineness (FC) and recycled aggregates on the engineering properties and micro structure of high volume blast furnace slag (BS) concrete with 75% BS and 21 MPa. FC manufactured by particle classification at the plant with Blaine fineness of more than $7000cm^2/g$ was used as additional alkali activator for high volume blast furnace slag concrete made with recycled fine and coarse aggregates. FC was replaced by 15, 20 and 25% OPC. Test results showed that the incorporation of FC resulted in an increase in the compressive strength compared to BS concrete without FC by as much as 30% due to accelerated hydration and associated latent hydraulic reaction. It was found that the use of FC and recycled aggregates played an important role in activating BS for high volume BS concrete by offering sufficient alkali.

• Journal of Animal Environmental Science
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• v.9 no.2
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• pp.69-78
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• 2003

In this study, the energy conversion equipment from the radiation energy to mechanical energy by using n­pentane as the operating fluid was constructed and the performance to pump the water was tested for the utilization of solar powered water pump. The equipment was designed optimally, after the theoretical analyses of the water pumping head and water quantity per cycle were done. The pentane vapour temperature in the condenser and the temperature of the outlet water from the condenser became lowered and the heat transfer rate became higher with decreasing the water inlet level to the condenser. The temperature difference between the condenser and the water tank was significant. Therefore, the distance between the water tank and condenser was recommended to be shorten and the diameter of their connecting pipe was recommended to be narrow in order to reduce the resistance of the fluid passage and improve the heat transfer rate. The amount of water pumped was 1.6­2.4 liters. Mass flow rate of the cooling water became lowered when the cooling water pipe was prolonged from the condenser to improve the heat transfer rate.

• Clean Technology
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• v.13 no.4
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• pp.293-299
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• 2007

Direct coating of catalyst layer on the $Nafion^{(R)}$ membrane has been optimized in the process of fabrication of membrane electrode assembly (MEA) to enhance the performance of direct methanol fuel cell (DMFC). In this method, the contact resistance at the interface of the catalyst layer and the membrane was found to be low. The effect of catalyst loading, thickness of membrane and the gas diffusion layer (GDL) with or without the presence of micro-porous layer (MPL) on the performance of the MEA was also investigated. The MEA fabricated by the above-mentioned method exhibited a performance of $147\;mW/cm^2$ and $100\;mW/cm^2$ at $80^{\circ}C$ and $60^{\circ}C$, respectively, with the catalysts loading of $4\;mg/cm^2$.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.389-400
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• 2017

Based on U-shaped composite beam, the new form of AU-composite beam were developed to create economical and efficient components reducing the cost and shortening the length of construction work. Because the U-shaped sections are open and needs to be fixed by topping concrete securely. Therefore, it is required to maintain the U-shaped sections in a structure and to work in the safe condition through construction. It also requires accessories that resist the horizontal shear force for synthesis between the top and bottom of the U-shaped section. To reinforce these shortcomings, a shear connector has been developed with various purposes of steel plate anchors. In this study, the steel plate anchors were directly tested and the shear force was evaluated by the horizontal shear force. The experiment was divided into two types, depending on the applicable deck plates. As a result of the experiment, the continuous type specimens showed greater resistance in both strength and displacement than the ones of stud anchor specimen. In discontinuous type case, due to shear simulations and simple element analysis, the less increase the ratio of width to height and the more shear strength decreased. Thus, the shear strength equation of the stud anchor was modified to suggest the new shear strength based on the testing results.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.159-167
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• 2017

A precast concrete deck system is considered an effective alternative in terms of its rapid construction and quality assurance than cast-in-place concrete deck. In precast concrete deck system, structural performance and serviceability are mostly determined by the connection methods between the precast decks. This research proposes more improved precast deck system with asymmetric ribbed connection details improving the disadvantage of previous precast deck system such as difficulties in assembling precast decks. And in this precast deck system, a separate form is not required at the site because partition wall of the precast decks serves as a form when placing non-shrinkage mortar in the connection part of the precast decks. Therefore, rapid construction is possible. Flexural performance is verified through load tests considering main parameter such as rib length in the precast deck connection. From the test results, it can be inferred that the development of the rebar and prevention of adhesion failure in the partition wall of the precast deck system are important factors in securing the flexural performance. Although the structural performance of the precast deck system with asymmetric connection details is gradually reduced as the rib length in the precast deck connection increases, the proposed precast deck system shows sufficient flexural performance and can be applied to the connection part of precast decks effectively.