• Environmental Engineering Research
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• v.24 no.4
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• pp.630-637
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• 2019

The present study aimed to investigate the potential of Enterococcus faecalis (E. faecalis) and Bacillus cereus (B. cereus) in improving the properties of bio-concrete. E. faecalis and B. cereus strains were obtained from fresh urine and an acid mire water at cell concentration of 1.16×10¹² and 1.3×10¹² cells mL^-1, respectively. The bacterial strains were inoculated in a liquid medium into the concrete with 1, 3 and 5% as replacement of water cement ratio (w/c). The ability of E. faecalis and B. cereus cells to accumulate the calcite and the decrement of pores size within bio-concrete was confirmed by SEM and EDX analysis. The results revealed that E. faecalis exhibited high efficiency for increasing of compressive and splitting tensile strength than B. cereus (23 vs. 14.2%, and 13 vs. 8.5%, respectively). These findings indicated that E. faecalis is more applicable in the bio-concrete due to its ability to enhance strength development and reduce water penetration.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.488-503
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• 1999

The present paper considers the constraint effect on J-R curves under the two-parameter $J-A_2$ controlled crack growth within a certain amount of crack extension. Since the parameter $A_2$ in $J-A_2$ three-term solution is independent of applied loading under fully plasticity or large-scale defor-mation $A_2$ is a proper constraint parameter uring crack extension. Both J and $A_2$ are used to char-acterize the resistance curves of ductile crack growth using J as the loading level and $A_2$ are used to char-acterize the resistance curves of ductile crack growth using J as the loading level and A2 as a con-straint parameter. Approach of the constraint-corrected J-R curve is proposed and a procedure of transferring the J-R curves determined from standard ASTM procedure to non-standard speci-mens or real cracked structures is outlined. The test data(e.g. initiation toughness JIC and tearing modulus $T_R$) of Joyce and Link(Engineer-ing Fracture Mechanics 1997, 57(4) : 431-446) for single-edge notched bend[SENB] specimen with from shallow to deep cracks is employed to demonstrate the efficiency of the present approach. The variation of $J_{IC}$ and $T_R$ with the constraint parameter $A_2$ is obtained and a con-straint-corrected J-R curves is constructed for the test material of HY80 steel. Comparisons show that the predicted J-R curves can very well match with the experimental data for both deep and shallow cracked specimens over a reasonably large amount of crack extension. Finally the present constraint-corrected J-R curve is used to predict the crack growth resistance curves for different fracture specimens. over a reasonably large amount of crack extension. Finally the present constraint-corrected J-R curve is used to predict the crack growth resistance curves for different fracture specimens. The constraint effects of specimen types and specimen sizes on the J-R curves can be easily obtained from the constrain-corrected J-R curves.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.4
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• pp.388-396
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• 2011

Sun tracking system is the most important subsystem in parabolic dish type solar thermal power plant, since it determines the amount of thermal energy to be collected, thus affects the efficiency of solar thermal power plant most significantly. Various types of sun tracking systems are currently used. Among them, use of photo sensors to located the sun(which is called sensor type) and use of astronomical algorithm to compute the sun position(which is called program type) are two of the mostly used methods. Recently some uses CCD sensor, like CCD camera, which is called image processing type sun tracking system. This work is concerned with the analysis of sun tracking performance of various types of sun tracking systems currently used in the parabolic dish type solar thermal power plant. We first developed a sun tracking error measurement system. Then, we evaluate the performance of five different types of sun tracking systems, sensor type, program type, hybrid type(use of sensor and computed sun position simultaneously), tracking error compensated program type and image processing type. Experimentally obtained data shows that the tracking error compensated program type sun tracking system is very effective and could provide a good sun tracking performance. Also the data obtained shows that the performance of sensor type sun tracking system is being affected by the cloud significantly, while the performance of a program type sun tracking system is being affected by the sun tracking system's mechanical and installation errors very much. Finally image processing type sun tracking system can provide accurate sun tracking performance, but costs more and requires more computational time.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.86-92
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• 2013

$SF_6/O_2$ inductively coupled plasmas were employed to texture Si surface as a pretreatment for nanocrystalline diamond film growth. It was found that the $SF_6/O_2$ plasma texturing provided a very wide process window where normalized roughness values in the range of 2~16 could be obtained. Significantly improved nucleation densities of ${\sim}6.5{\times}10^{10}cm^{-2}$ compared to conventional mechanical abrasion were achieved after seeding for the textured Si substrate.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.245-252
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• 2020

Unexpected equipment defects can cause a huge economic losses in the society at large. Although condition monitoring can provide solutions, the signal processing algorithms must be developed to predict mechanical failures using data acquired from various sensors attached to the equipment. The signal processing algorithms used in a condition monitoring requires high computing efficiency and resolution. To improve condition monitoring on a wireless sensor network(WSN), data visualization can maximize the expressions of the data characteristics. Thus, this paper proposes the extraction of visual feature from temperature data over time using condition monitoring based on a WSN to identify environmental conditions of equipment in a large-scale infrastructure. Our results show that time-frequency analysis can visually track temperature changes over time and extract the characteristics of temperature data changes.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.12-18
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• 2015

Recently, the development trend of turbomachinery is high capacity and high efficiency. Most of turbomachinery in the market are adopting ball bearings or air foil bearings. However, ball bearings have a limit for high speed product over $2.0{\times}10^6DN$(product of the inner diameter of the bearing in mm (D) and the maximum speed in rpm (N)). Air foil bearings have a limit for high axial load for high power products over 200~300 HP(horse power). Magnetic bearing is one of the solutions to overcome the limits of high speed and high axial load. Because magnetic bearings have no friction between the rotor and the bearings, they can reduce the load of the motor and make it possible to increase the rotating speed up to $5.0{\times}10^6DN$. Moreover, they can have high axial load capacity, because the axial load capacity of magnetic bearing depends on the capacity of the designed electromagnet. In this study, the radial and thrust magnetic bearings are designed to be applied to the 200 HP class turbo blower, and their performance was evaluated by the experiment. Based on the tests up to 26,400 rpm and 21,000 rpm under the no-load and load condition, respectively, it was verified that the magnetic bearings are stably support the rotor of the turbo blower.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.62-67
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• 2004

Many ships in voyage experience weight and buoyancy distribution change by various reasons such as change of sea water density and waves, weather condition, and consumption of fuel, provisions, etc . The weight and buoyancy distribution change can bring the ships out of allowable trim, heeling angle. In these case, the ships should adjust trim and heeling angle by shifting of liquid cargo or ballasting, deballasting of ballast tanks for recovery of initial state or for a stable voyage. But, if the adjustment is performed incorrectly, ship's safety such as longitudinal strength, intact stability, propeller immersion, wide visibility, minimum forward draft cannot be secured correctly. So it is required that the adjustment of trim and heeling angle should be planned not by human operators but by optimization computer algorithm. To make an optimized plan to adjust trim and heeling angle guaranteeing the ship's safety and quickness of process, Uk! combined mechanical analysis and optimization algorithm. The candidate algorithms for the study were heuristic algorithm, meta-heuristic algorithm and uninformed searching algorithm. These are widely used in various kinds of optimization problems. Among them, heuristic algorithm $A^\ast$ was chosen for its optimality. The $A^\ast$ algorithm is then applied for the study. Three core elements of $A^\ast$ Algorithm consists of node, operator, evaluation function were modified and redefined. And we analyzed the $A^\ast$ algorithm by considering cooperation with loading instrument installed in most ships. Finally, the algorithm has been applied to tanker ship's various conditions such as Normal Ballast Condition, Homo Design Condition, Alternate Loading Condition, Also the test results are compared and discussed to confirm the efficiency and the usefulness of the methodology developed the system.

• Korean Institute of Interior Design Journal
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• v.17 no.2
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• pp.13-21
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• 2008

The purpose of this study is to analyze the development and characteristics of movable-housing planning concept. A document research method was used to analyze and classified the development of the movable-housing concept of 20th century. Through this study, the following conclusions have been reached; First, the origin of the movable-housing is from the prehistoric and traditional portable buildings, also due to the emergence of nomadic lifestyle using car traveling and mobile home in the 1920's. Second, the development of the movable-housing in 20th century was classified as follows; (1) In order to obtain the productivity and efficiency drawing from the industrialized-housing in the early of 1900s, movable furniture and flexibility was proposed. (2) American mobile home in 1920's, influenced by the development of car industry, was the most successful example of a factory-built building to be found in the world. (3) Dymaxion house and dome by R.B.Fuller, an aggregation of high-tech mechanical equipment, had a great impact on the development the concept of 'mobility' and influenced Archigram & Metabolist's movable capsule ideas in 1960's. (4) The lightweight materials such as plastic, duralumin and pneumatic structure were adopted for movable-housing in 1960's. Through this research, It is discovered that the stage of social development has close links with the developing aspects of movable-housing concepts. This study shows that the combination of three planning concepts such as flexible housing, mobile-housing and capsule will be more ideal in movable-housing planning rather than relying on just one type.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.1
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• pp.34-42
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• 2001

A battery is the device that transforms the chemical energy into the direct-current electrical energy directly without a mechanical process. Unit cells are connected in series to obtain the required voltage, while being connected in parallel to organize capacity for load current and to decrease the internal resistance for corresponding the sudden shift of the load current. Because the voltage droop down in one set of battery is faster than in tow one, it amy result in the low efficiency of power converter with the voltage drop and cause the system shutdown. However, when the system being driven in parallel, a circular-current can be generated. The changing current differs in each set of battery because the system including batteries, rectifiers and loads is connected in parallel and it makes the charge voltage constant. It is shown that, as a result the new batteries are heated by over-charge and over-discharge, and the over charge current increases rust of the positive grid and consequently shortens the lifetime of the new batteries. The difference between the new batteries and old ones is the amount of internal resistance. In this paper, we can detect the unbalance current using the micro-processor and achieve the balance current by adjusting resistance of each set. The internal resistance of each set becomes constant and the current of charge and discharge comes to be balanced by inserting the external resistance into the system and calculating the change of internal resistance.

• Resources Recycling
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• v.16 no.6
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• pp.46-51
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• 2007

This study aimed at developing high-efficiency RDF(refuse derived fuels) fuel in order to use RDF energy rationally and to recycle industrial product. As most studies in this area are concentrated in large combustion apparatuses such as kilns, but this study was focused on the small-sized heating systems, applying them directly to grate type boiler which has a heating capacity of $66{\sim}132m^2$. The different kinds of fuel are experimented including RDF. Coke and Waste Tire. First, for this, we experimented and analyzed RDF to see the change in its mass and heating value. Also, four kinds of exhaust gas are sampled by gas analyzer including CO, $CO_2$, NO and $NO_2$ at different temperature. As a result, the levels of CO concentration of RDF are higher than these of coke and waste tire. But, the levels of NO, $CO_2$ and $SO_2$ concentration of RDF and coke were lower then the levels when waste tire is burned.