• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.895-905
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• 2001

This paper presents vector fields, three dimensional mean velocities, turbulent intensities, turbulent kinetic energy and Reynolds shear stresses measured in the X-Y plane of the gas swirl burner with a cone type baffle plate by using an X-type hot-wire probe. This experiment is carried out at the flow rates of 350 and 450ℓ/min which are equivalent to the combustion air flow rate necessary to release 15,000 kcal/hr in a gas furnace. The results show that the maximum axial mean velocity component exists around the narrow slits situated radially on the edge of a burner. Therefore, there is some entrainment of ambient air in the outer region of a burner. The maximum values of turbulent intensities occur around the narrow slits and in front of a burner up to X/R=1.5. Moreover, the turbulent intensity components show a relatively large value in the inner region due to the flow diffusion and mixing processes between the inclined baffle plate and the swirl vane. Consequently, the combustion reaction is expected to occur actively near these regions.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.537-543
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• 2003

This paper presents the improved procedure to assess static and dynamic strength of crawler type excavators. A fully integrated model including front attachment and chassis was prepared for structural analysis. In this paper, two types of loading input methods were investigated and the method imposing digging force directly on bucket tooth was more convenient than imposing cylinder reaction force on cylinder pin even if the two methods showed no discrepancy in analysis results. Static strength analysis was carried out for eight analysis scenarios based on two extreme digging positions, maximum digging reach position and maximum digging force positions. The results from static strength analysis were compared with measured stresses, cylinder pressures and digging forces and showed a good quantitative agreement with measured data. Dynamic strength analysis was carried out for simple reciprocation of boom cylinders. It was recognized that the effect of compressive stiffness of hydraulic oil was very important for dynamic structural behavior. The results from dynamic strength analysis including hydraulic oil stiffness were also compared with measured acceleration data and showed a qualitative agreement with measured data.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.65-70
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• 2001

OH radical and NOx have been measured in a methane-air partially premixed flame using PLIF technique to define preheated air combustion characteristics. The temperature of mixture is determined by 300K, 400K, 600K and 800K below the auto-ignition temperature respectively. Flame height increases as equivalence ratio increased. As initial enthalpy is supplied, the radius of flame was increased and much amount of yellow flame in rich equivalence ratio was observed. This is due to the faster burning velocity. Also initial oxidization begins earlier as the initial temperature of mixture increased. It means that height of premixed flame front decreased. This phenomenon can be observed OH PLIF image. The qualitative analysis of OH concentration in the PLIF image shows that overall OH concentration increases with equivalence ratio and the initial temperature of mixture increased. At the preheating temperature goes up, axial gradient of OH concentration is less steep than that of lower temperature condition. This may identify that combustion reacts continuously, so preheated air combustion can evade the local heating and make high temperature indiscriminately in the overall reaction zone.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4316-4320
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• 2011

The effects of various hydroxide compounds on base stacking (BS) were investigated for pre-concentration of DNA molecules in capillary electrophoresis (CE). In BS, hydroxide ions ($OH^-$) were electrokinetically introduced after DNA sample injection. A neutralization reaction occurred between the $OH^-$ and $Tris^+$ of the running buffer, which resulted in a zone of lower conductivity. Within the low conductivity zone of the high electric field, the DNA molecules moved more rapidly and were concentrated in front of the low conductivity zone. At the same BS conditions of CE, the enhanced sensitivity of the DNA samples was dependent on the kind of multivalent cations in the hydroxide compounds. Except for LiOH, the hydroxide compounds with monovalent cations showed more effective BS than those with divalent cations because of solubility, ionic strength and electronegativity. The order of hydroxide compounds that enhance the detection sensitivity of DNA molecules was as follows: NaOH > $NH_4OH$ > KOH > $Ba(OH)_2$ > $Sr(OH)_2$ > LiOH > $Ca(OH)_2$ > $Mg(OH)_2$. $NH_4OH$, KOH and $Ba(OH)_2$ proved to be efficient hydroxide compounds to use as effective BS reagents in CE instead of NaOH.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.54-64
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• 1988

This paper assesses the models in the SCDAP code using the results of the FLHT-2 test. Calculations show that the SCDAP correctly predicts Ire temperatures, oxidation front movement, overall hydrogen generation and peak generation rate, internal fuel rod pressure, and cladding rupture due to ballooning. A comparison of the calculated results with measured data shows that two phase level is underpredicted, and that radiation heat transfer and auto-catalytic reaction temperature of zircaloy are overpredicted. These models are recommended to be modified. The analysis also shows that the simulation of the gap in a fuel rod improves the code prediction on core damage progression.

• Computers and Concrete
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• v.21 no.4
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• pp.471-484
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• 2018

Refined analysis depicting mass transportation and physicochemical reaction and reasonable computing load with acceptable DOFs are the two major challenges of numerical simulation for concrete durability. Mesoscopic numerical simulation for chloride diffusion considering binder, aggregate and interfacial transition zone is unable to be expended to the full structure due to huge number of DOFs. In this paper, a multiscale approach of combining both mesoscopic model including full-graded aggregate and equivalent macroscopic model was introduced. An equivalent conversion of chloride content at the Interfacial Transition Layer (ITL) connecting both models was considered. Feasibility and relative error were discussed by analytical deduction and numerical simulation. Case study clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Difference for single-scale simulation and multiscale approach was observed. Finally, this paper addressed some worth-noting conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar placement, rebar diameter, concrete cover and exposure period.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.4
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• pp.34-41
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• 1995

The structure of premixed tubulent flames in a constant-volume vessel was investigated using a schlieren method and microprobe method. The schlieren method was used to observe the flame structure qualitatively. The microprobe method, which detects a flamelet by detecting its flame potential signal, was used to investigate the deeper flame structure behind the flame front. The flame potential signal having one to six peaks was obtained in the case of turbulent flames, each of them being regarede as a flamelet existing in the flame zone. Based on this consideration, the flame propagation speed, the thickness of the flame zone, the number of flamelets and the separation distance between adjacent flamelets in the flame zone were measured. Moreover, the thickness of flamelet which could not be attempted in the conventional electrostatic probe method was also investigated. The experimental results of this work suggest the existence of "reactant islands" in the reaction zone, and show that the averaged number of flamelets increases with an increase in the turbulence intensity and/or a decrease in the Damkohler number. The mean thickness of flamelet in the case of turbulent flames was found to be about two times compared to laminar values.ar values.

• The Korean Journal of Pain
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• v.8 no.1
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• pp.149-151
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• 1995

Piriformis syndrome is a syndrome of low back and leg radiating pain thought to be due to a chronic contracture of the piriformis muscle that causes irritation of the sciatic nerve. The piriformis muscle is a flat pyramidal muscle, an external rotator and abductor of the hip, originating from the front of the sacrum and inner aspect of the sacroiliac joint, then passes laterally out of the sciatic notch to attach posteriorly to the greater trochanter of the femur, the sciatic nerve passes between the two bellies of the muscle. Mechanical irritation of the sciatic nerve by an inflammatory reaction of the piriformis muscle and its fascia at this pelvic level causes pain to radiate in the dermatomal regions of the nerve roots similar to that disk entrapment. diagnosis of piriformis syndrome is made primary on the basis of history and clinical examination. The incidence is considerably higher in women, with the reported ratio of women to men of 6:1. These patients frequently present with associated symptoms of pelvic pain and/or dyspareunia. Symptoms are usually unilateral but occasionally be bilateral. We had a 42 year-old woman patient with low back and left leg radiating pain and dyspareunia treated by caudal steroid and local anesthetic.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.914-922
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• 2002

Thermo-acoustic waves can be thermally generated in a compressible flow field by rapid heating and cooling, and chemical reaction near the boundary walls. This mechanism is very important in the space environment in which natural convection does not exist. Also this may be a significant factor for heat transfer when the fluids are close to the thermodynamic critical point. In this study, the generation and transmission characteristics of thermo-acoustic waves in an air-filled confined domain with two-step pulsed heating are studied numerically. The governing equations are discretized using control volume method, and are solved using PISO algorithm and second-order upwind scheme. For the purpose of stable solution, time step was set to the order of $1\times10_-9s,\;and\;grids\;are\;50\times2000$. Results show that temperature and pressure distributions of fluid near the boundary wall subjected to a rapid heating are increased abruptly, and the induced thermo-acoustic wave propagates through the fluid until it decays due to viscous and heat dissipation. Pressure waves have sharp front shape and decay with a long tail in the case of step heating, but these waves have sharp pin shape in the case of pulsed heating.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.77-84
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• 2010

Reduction of oxides has been investigated for the volume reduction and recycling of the spent oxide fuel from commercial nuclear power plants. Various oxide reduction methods were proposed and KAERI (Korea Atomic Energy Research Institute) is currently developing an electrochemical reduction process using a LiCl-$Li_2O$ molten salt as a reaction medium. The electrochemical reduction process, the front end of the pyroprocessing, can connect the PWR (Pressurized Water Reactor) oxide fuel cycle to a metal fuel cycle of the sodium cooled fast reactor. This paper summarizes KAERI efforts on the development, improvement, and scale-up of the oxide reduction process.