• International Journal of Knowledge Content Development & Technology
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• v.14 no.2
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• pp.81-97
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• 2024

The study investigated computer literacy skills as a determinant of electronic reference sources utilization among selected secondary school students in Ado-Odo Ota Local Government, Ogun State, Nigeria. Four specific objectives with conforming research questions guided the study. Descriptive survey research design was adopted for the study. The population of the study comprises of SSS3 students of the three selected Community Secondary Schools in Ado Odo Ota. A sample size of 150 was used for the study. The instrument for data collection was a self-developed structured questionnaire. Data collected was analyzed using frequency and percentages. Findings of the study revealed that majority of secondary school students were not aware of the availability of electronic reference sources. It also revealed that the level of their computer literacy skills was below average. Majority of them have never used computer before and the few of them that have used computer before used it in their homes, their friend's homes or in the cyber café. It was found that lack of formal training on the use of electronic reference sources, lack of access to computer, lack of awareness of availability of electronic reference sources, lack of funds for internet subscriptions, over dependency on printed reference sources and lack of motivation to use electronic reference sources were the major hindrances to the use of electronic reference sources among secondary school students. It was recommended that the school librarians and teachers should play a role in creating awareness among secondary school students about the availability of online/ electronic reference sources among others.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.580-586
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• 2002

The effect of processing and designing variables such as pouring temperature(1400 or $1500^{\circ}C$), inoculation and risering design(T and H type) on the formation of defects such as external depression, primary and secondary shrinkage cavities in GC150 gray cast iron was investigated. In T type risering design, external depression or primary shrinkage cavity due to liquid contraction was formed in all of the eight cases. Regardless of its modulus value, the riser could not function properly in T type risering design because directional solidification was not promoted toward the riser. On the other hand, the four cases of H type risering design in which thermal sleeves were set onto the risers produced defect-free castings. In both types of the risering designs, secondary shrinkage cavity caused by solidification contraction was not observed in the casting because of the expansion pressure due to graphite precipitation and the application of rigid pep-set mold. The degree of external depression or primary shrinkage cavity was reduced with lowered pouring temperature. The effect of inoculation was diminished because of the high carbon equivalent of GC 150 gray cast iron.

• Computational Structural Engineering
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• v.10 no.3
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• pp.225-231
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• 1997

The dynamic characteristics of Control Element Drive Mechanism(CEDM) for Korea Standard Nuclear Power Plant are studied with the CEDM modeled as a secondary mass in a simplified two degree of freedom system, while the reactor vessel as a primary mass. The optimal .mu.-f curve is developed to reduce the response amplitudes of both primary and secondary masses. In order to improve a design it is proposed that the natural frequency ratio, f, should be converged to 0.93, the mass ratio, .mu., should not be reduced, and the result should be converged to the optimal .mu.-f curve. Optimal design for CEDM components has been carried out and the response amplitude ratios of reactor are reduced 10.5 - 19.7% while those of CEDM are reduced 6.3 - 3.4%.

• Journal of Power Electronics
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• v.7 no.1
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• pp.13-20
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• 2007

LLC resonant converters display many advantages over the conventional LC series resonant converter such as narrow frequency variation over wide range of load and input variation and zero voltage switching even under no load conditions. This paper presents analysis and design consideration for the half bridge LLC resonant converter. Using the fundamental approximation, the gain equation is obtained, where the leakage inductance in the transformer secondary side is also considered. Based on the gain equation, the practical design procedure is investigated to optimize the resonant network for a given input/output specifications. The design procedure is verified through an experimental prototype of the 115W half-bridge LLC resonant converter.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.413-420
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• 1998

In this study, optimum design methodology for rail vehicle suspension characteristics is suggested. Three parameters, primary lateral/longitunal stiffness and secondary lateral stiffness, are selected as design parameters. critical speed, suspension stroke trade-off and derailment coefficient are selectee as performance constraints. The optimum parameters to maximize ride quality are evaluated under the constraints. Steady-state curiving model to be able to evaluate derailment coefficient is developed. The combined design procedure is developed to evaluate Three parameters at the same time.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.411-412
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• 2002

Piston-cylinder system are widely used in power engineering applications. In reciprocating refrigeration compressors, where extremely low friction losses are required, ringless pistons are being used to diminish the friction between piston rings and cylinder wall. Since the ringless piston has the freedom of lateral motion there is a potential danger that it will occasionally hit the cylinder wall while moving up and down along it's axis. A good design must therefore provide a smooth and stable reciprocating motion of the piston and ensure that the fluid film separating the piston from the cylinder wall is maintained all times. And the compromise between refrigerant gas leakage through the piston-cylinder clearance and the friction losses is required utilizing a dynamic analysis of the secondary motion for the high efficiency compressor. To this end, the computer program is developed for calculating the entire piston trajectory and the lubrication characteristics as functions of crank angle under compressor running conditions. The results explored the effects of some design parameters and operating conditions on the stability of the piston, the oil leakage, and friction losses.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.777-782
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• 2000

The flow fields in the volute casing of a small-size turbo-compressor at different flowrate (design point ${\pm}20%$) are studied by numerical analysis. The governing equations for three-dimensional steady viscous flow are solved using SIMPLE algorithm with commercial code of STAR-CD. Numerical results show that the three-dimensional flow pattern inside the volute casing of a small-size turbo-compressor is strongly influenced by secondary flows that are typically created by the curvature or the casing passages. The flow pattern in the casing also affects the performance of the turbo-compressor. In order to elucidate the loss mechanism through the volute, we prepared the secondary flow, velocity magnitude, and static pressure distribution at the four cross-sectional planes of the casing.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.496-501
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• 2003

Computational study is performed to understand the fluidic thrust vectoring control of an axisymmetric nozzle, in which secondary gas injection is made in the divergent section of the nozzle. The nozzle has a design Mach number of 2.0, and the operation pressure ratio is varied to obtain the different flow features in the nozzle flow. The injection flow rate is varied by means of the injection port pressure. Test conditions are in the range of the nozzle pressure ratio from 3.0 to 8.26 and the injection pressure ratio from 0 to 1.0. The present computational results show that, for a given nozzle pressure ratio, an increase of the injection pressure ratio produces increased thrust vector angle, but decreases the thrust efficiency.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.116-125
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• 2010

In this study, a novel hydraulic energy-regenerative system was presented from its proposal through its modeling to its control. The system was based on a closed-loop hydrostatic transmission and used a hydraulic accumulator as the energy storage system in a novel configuration to recover the kinetic energy without any reversion of the fluid flow. The displacement variation in the secondary unit was reduced, which widened the uses of several types of hydraulic pump/motors for the secondary unit. The proposed system was modeled based on its physical attributes. Simulation and experiments were performed to evaluate the validity of the employed mathematical model and the energy recovery potential of the system. The experimental results indicated that the round trip recovery efficiency varied from 22% to 59% for the test bench.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.410-418
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• 2024

Study of flow behavior within rod bundles has been an active topic. Surface modification technologies are important parts of the design of the fourth generation reactor, which can increase the strength of the secondary flow within the rod bundle lattices. Quasi-periodic large-scale vortex structure (QLVS) is introduced by arranging micro ribs on the surface of rod bundles, which enhanced the scale of the secondary flow between the rod bundle lattices. Using computational fluid dynamics (CFD) and water experiments, the flow field distribution and drag coefficient of the rod-bundle lattices are studied. The secondary flow between the micro-ribbed rod-bundle lattice is significantly enhanced compared to the standard rod-bundle lattice. The numerical simulation results agree well with the experimental results.