• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.331-340
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• 2000

The existing two-phase biological fluidized bed has some problems such as limit of oxygen transfer and blockade of fluidized distributor. In this study, three-phase swirl flow biological fluidized bed has designed to solve the problems and to investigate its running characteristics. TOC of influent synthetic wastewater was approximately $70mg/{\ell}$. HRT of reactor was 1.6 hours. Mean particle size of sand, as packing media, was 0.397mm and packing volume was varied from $200m{\ell}/{\ell}$ to $600m{\ell}/{\ell}$ by stages in the bed. The amount of biomass and effluent water quality was throughly investigated in the bed. Showing experiment results from the above conditions, it was possible to solve the problems of existing fluidized bed and to keep DO of $3mg/{\ell}$ or more. And it was also TOC removal rate of 91 to 94 %, MLVSS of 2,360 to $3,860mg/{\ell}$, MLVSS per g-media of 8.4 to 17.3 mg/g, F/M ratio of 0.59 to $1.04kg-TOC/kg-MLVSS{\cdot}day$, biofilm thickness of $35{\sim}71{\mu}m$ and sludge productivity of 1.03 to $2.35kg-SS/m^3{\cdot}day$. Optimal conditions in this experimental were as follows.; those were biofilm thickness of approximately $54{\mu}m$. MLVSS per g-media of 13 mg and media packing volume of 350 to $400m{\ell}/{\ell}$ when F/M ratio was low, treatment efficiency was high and sludge productivity was low. Showing the media with optics microscope in this optimal condition, attached microbes such as Epistylis sp. were observed. From SEM photographs, it showed that Coccus adhere to and grow on the media surface.

• Applied Microscopy
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• v.34 no.1
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• pp.71-81
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• 2004

When U. unicinctus mature oocytes were fertilized in vitro, germinal vesicle breakdown (GVBD) and meioses occurred and the zygotes entered cleavage stage. A modified pattern of spiral cleavages, suggestively based on behavior of mitotic spindles, have been observed in this work. The first and second cleavages were meridional and the third was equatorial, and then followed by repetitions of meridional-equatorial cleavage. The cleavage of the isolecithal egg were equal and holoblastic and its patterns were spiral. The anti-${\alpha}-,-{\beta}$- tubulin reactions and confocal microscopy revealed mitotic apparates tilted obliquely at each mitosis causing oblique displacements of the blastomeres. Despite isolecithal distribution of yolk, this observations implicated that tilting of mitotic apparates induced spiral cleavage and the displacements of blastomeres. However, these features would not be the typical spiral cleavage, but represented a modified pattern of known Spiralian s in the sense of the equal cleavage. During the first cleavage, heart-shaped eggs have been produced. Electron microscopies exhibited the first cleavage furrow extended with its membranous structure deeply into the cytoplasm. Contractile ring has not been observed.

• Journal of the Korean Society of Radiology
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• v.14 no.1
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• pp.69-75
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• 2020

Multilayer mirrors have widely been used not only in the industry but also in the medical field. X-ray reflectivity was measured by X-ray diffractometer to evaluate the performance of W/C multilayer mirror with 40 layers. Genetic algorithm are used to obtain thickness, density, and interfacial roughness for each of the 40 layers. The existing uniform random selection causes a problem that the solution does not converge or the error increases even if it convergence. To reduce the time to calculate the fitness of the genetic algorithm, the genetic algorithm was written in C/C++ parallel programming. The genetic algorithm showed excellent scalability of linear time increase with increasing number of generation and population. The genetic algorithm was selected with uniform and Gaussian randomness of 1:1 to improve the convergence of solution. The improved genetic algorithm can be applied to characterize each layer of a sample with more than a few tens of layers, such as a multilayer mirror.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.1
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• pp.30-35
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• 2000

The experimental study on the lift-off height of diffusion flames was conducted to investigate the damage of swirl-coaxial injector used in $GO_2$/kerosene rocket engine during initial stage of ignition. To investigate the causes of damage and to prevent further damage of the injector, experimental injector was designed and hot fire tests were performed with varying propellant momentum ratio($\frac{Momentum of {GO_2}}{Momentum of Kerosene}$) from 1 to 12. In experimental coaxial injector, kerosene is sprayed from the central nozzle with swirl and $GO_2$ sprayed around the kerosene nozzle in the direction parallel to the axis of combustion chamber. Chamber pressure are close to the atmospheric condition. Lift-off height was measured by still images from camcoder and average values were used as data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3296-3301
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• 2011

The Porous pavement gains popularity because of several benefits. It is to minimize hydro-planning condition, spraying condition, and splash to increase friction resistance, and decrease noise. Also, other studies showed that it is important to have appropriate porosity to reduce noise and water flush. The purpose of this study is an evaluation on the mechanical properties of asphalt pavements for surface course. In this study the specimen was manufactured using the Gyratory compactor in order to compact the strengthened surface course that involved the two-layer pavement. This study is conducted by using Marshall stability test(KS F 2377), Impact resonance test, Schmidt hammer test(KS F 2730), and the Uniaxial compression test(KS F 2314). Using the Uniaxial compression test and Schmidt hammer test, the values of compressive strength and bearing capacity were measured, and the modulus of elasticity for each specimen was respectively measured using the Uniaxial compression test, Impact Resonance test.

• The Journal of Engineering Geology
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• v.15 no.4 s.42
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• pp.447-462
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• 2005

The purposes of this study are to evaluate and discuss the importance of geochemical properties of soil materials that play an important role in the occurrence of the landslide, using analyses of microtexture, particle size distribution, XRC, and FE-SEM equipped with energy dispersive spectrum on soils collected from landslide slopes of gneiss, granite and sedimentary rock areas. Soils from gneiss and granite areas where landslides took place have much clay content relative to those from non landslide areas, particularly pronounced in the granite area. Therefore the clay content is considered a sensitive factor on landslide. Clay minerals contained in soils are illite, chlorite, kaolinite and montmorillonite. Especially the content of clay minerals in soils from the Tertiary sedimentary rocks is highest, with abundant montmorillonite as expandable species. It is believed that this area was much vulnerable to landslide comparable to other areas because of its high content of monoorillonite, even though there might be weak precipitation. Since no conspicuous differentiation in mineralogy between the landslide area and non landslide area can be made, the occurrence of landslide may be influenced not by mineralogy, but by local geography and mechanical properties of soils. Geochemical information on weathering properties, mineralogy, and microtexture of soils is helpful to better understand the causes and patterns of landslide, together with engineering geological analyses.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.965-972
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• 2016

This paper presents results of flight experiments on a navigation algorithm including multiplicative extended Kalman filter for estimating attitude of the guided munition. The filter describes orientation of aircraft by data fusion with low-cost sensors where measurement update is done by multiplication, rather than addition, which is suitable for quaternion representation. In determining attitude from vector observations, the existing approach utilizes a 3-axis accelerometer as a 2-axis inclinometer by measuring gravity to estimate pitch and roll angles, while GNSS velocity is used to derive heading of the vehicle. However, during accelerated maneuvers such as coordinated flight, the accelerometer provides inadequate inclinometer measurements. In this paper, the measurement update process is newly defined to complement the vulnerability by using different vector observations. The acceleration measurement is considered as a result of a centrifugal force and gravity during turning maneuvers and used to estimate roll angle. The effectiveness of the proposed method is verified through flight experiments.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.138-152
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• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.33-42
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• 2021

Modern aircraft fighters improve the maneuverability and performance with the RSS (Relaxed Static Stability) concept and therefore these aircrafts are susceptible to abrupt pitch-up in the transonic and moderate Angle-of-Attack (AoA) flight region where the shock wave is formed and the mean aerodynamic center is moved forward during deceleration. Also, the modeling of the aircraft flying in this flight region is very difficult due to complex flow filed and unpredictable dynamic characteristics and the model-based control design technique does not fully cover this problem. In this paper, we analyzed the performance of the TPMC (Transonic Pitching Moment Compensation) control based on the model-based IDI (Incremental Dynamic Inversion) and the Hybrid IDI based on the model and sensor based IDI during the SDT (Slow Down Turn) in transonic region. As the result, the Hybrid IDI had quicker response and the same maximum g suppression performance and provided the predictable flying qualities compared to the TPMC control. The Hybrid IDI improved the performance of the Over-G protection controller in the transonic and moderate AoA region

• Conservation Science in Museum
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• v.8
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• pp.49-69
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• 2007

This is about the scientific analysis of the 10 items of the gilt-bronze Panbul excavated from Anapji, Gyeongju. First, the composition of the Panbul was confirmed, using X-ray fluorescence spectrometer (XRF), and the patinas covering the surface of the Panbul were analyzed, using X-ray diffractometer (XRD). And the micro structures and gilt layer of the Panbul were investigated, using microscope and scanning electron microscope with energy dispersive spectrometer (SEM/EDS), and in order to investigate the internal conditions of the Panbul, X-radiography was conducted. As the result, it is found out that the material of the Panbul excavated from Anapji was the bronze of copper (86~95%) and tin (4~12%), and coated with gold. And cuprite (Cu₂O) was detected from red patina of the gilt-bronze Panbul, and chalcocite(Cu₂S) also was detected from the black patina. As the result of the observation of the micro structure through microscope, it is estimated that it was manufactured, using the wax molding method, and, judging from the fact that the thickness of gilt layer was not even, and that the groove had been filled, it was presumed that the amalgam coating method had been used, but some questions still remain, because mercury was not detected. Lastly, through the X-radiography, it was observed that the tiny round spots existed, which was presumed to have been generated during the casting.