• Nuclear Engineering and Technology
• /
• v.49 no.3
• /
• pp.466-475
• /
• 2017

Coolant mixing under natural circulation flow regime constitutes a key parameter that may play a role in the course of an accidental transient in a nuclear pressurized water reactor. This issue has motivated some experimental investigations carried out within the OECD/NEA PKL projects. The aim was to assess the coolant mixing phenomenon in the reactor pressure vessel downcomer and the core lower plenum under several asymmetric steady and unsteady flow conditions, and to provide experimental data for code validations. Former studies addressed the mixing phenomenon using, on the one hand, one-dimensional computational approaches with cross flows that are not fully validated under transient conditions and, on the other hand, expensive computational fluid dynamic tools that are not always justified for large-scale macroscopic phenomena. In the current framework, an unsteady coolant mixing experiment carried out in the Rossendorf coolant mixing test facility is simulated using the three-dimensional porous media capabilities of the thermal-hydraulic system CATHARE code. The current study allows highlighting the current capabilities of these codes and their suitability for reproducing the main phenomena occurring during asymmetric transient natural circulation mixing conditions.

• Journal of Veterinary Clinics
• /
• v.39 no.3
• /
• pp.138-143
• /
• 2022

A 21-year-old female Halla Horse weighing 248 kg was referred to the Jeju National University Equine Hospital with the chief complaint of anorexia accompanied by general weakness and depression for the previous three days suspected to be related to colic. Extensive diagnostic tests were performed for the following six days, including complete blood count (CBC), serum chemistry, gastroscopy, x-rays, and ultrasound imaging. The signalment, history, symptoms, and test results strongly suggested a chronic intestinal inflammatory disease with or without an alimentary tumor; hence, an exploratory laparotomy was performed. Almost the entire small intestine wall was severely thickened with diffuse ecchymosis on the serosa and protruded nodules on the mucosa. A presumptive diagnosis of an intestinal tumor was made, and the patient was euthanized, considering the patient's welfare with poor prognosis and low expectancy. A massive part of the small intestine was collected and submitted for macroscopic and microscopic pathology evaluations. The pathologic examination, including immunohistochemistry (IHC), indicated equine intestinal lymphoma showing strong positivity for T cell marker. This report describes the clinical signs, diagnosis and pathological features of intestinal lymphoma in a Halla Horse in detail.

• Computers and Concrete
• /
• v.29 no.6
• /
• pp.361-374
• /
• 2022

On the premise of ensuring that the automatic and quantitative discharging function of concrete conveyors is met, the accuracy of the weight forecast by the mathematical model of the screw conveying volume is improved, and the error of the weight of the concrete parts and the accumulation thickness is reduced. In this paper, the discrete element method (DEM) is used to simulate the macroscopic flow of concrete. Using the concrete discrete element model, the size of the screw conveyor is set, and establish the response model between the influencing factors (process and structure) and the concrete mass flow rate according to the design points of the screw discharging experiment. The nonlinear data fitting method is used to obtain the volumetric efficiency function under the influence of process and structural factors, and the traditional screw conveying volume model is improved. The mass flow rate of concrete predicted by the improved mathematical model of screw conveying volume is consistent with the test results. The model can accurately describe the conveying process of concrete and achieve the purpose of improving the accuracy of forecasting the weight of discharged concrete.

• Nuclear Engineering and Technology
• /
• v.55 no.8
• /
• pp.2823-2834
• /
• 2023

Austenitic stainless steel welds (ASSWs) of nuclear components undergo aging-related degradations caused by high temperature and neutron radiation. Since irradiation leads to the change of material characteristics, relevant quantification is important for long-term operation, but limitations exist. Although ion irradiation is utilized to emulate neutron irradiation, its penetration depth is too shallow to measure bulk properties. In this study, a systematic approach was suggested to estimate mechanical properties of ion irradiated 308 ASSW. First of all, weld specimens were irradiated by 2 MeV proton to 1 and 10 dpa. Microstructure evolutions due to irradiation in δ-ferrite and austenite phases were characterized and micropillar compression tests were performed. In succession, dislocation density based stress-strain (S-S) relationships and quantification models of irradiation defects were adopted to define phases in finite element analyses. Resultant microscopic S-S curves were compared to verify material parameters. Finally, macroscopic behaviors were calculated by multiscale simulations using real microstructure based representative volume element (RVE). Validity of the approach was verified for the unirradiated specimens such that the estimated S-S curves and 0.2% offset yield strengths (YSs) which was 363.14 MPa were in 10% agreement with test. For irradiated specimens, the estimated YS were 917.41 MPa in 9% agreement.

• Journal of ILASS-Korea
• /
• v.27 no.1
• /
• pp.1-10
• /
• 2022

In this study, an experimental investigation on the effects of the pressure ratio on the wall-impingement spray characteristics of nitrogen gas using a compressed natural gas (CNG) injector was conducted. The transient development of the impingement spray was recorded by a high speed camera with Z-type Schlieren visualization method. The spray behavior under various pressure ratio conditions were analyzed. The experimental results showed that the pressure ratio has positive effect on the development of spray wall-impingement. The effects of the above factor were evaluated in a constant volume chamber at atmospheric conditions. The data from test showed that, with the increase of the pressure ratio, the spray tip penetration (STP) quickly increases before the impingement and gradually increases after the impingement. Additionally, the spray velocity first increases and then sharply decreases on regardless of the injection pressure level. As the spray spreading angle increases, spray area and volume increases rapidly with the increase in STP at the beginning of injection, and finally entered a stable range, has a great correlation with the increase of pressure ratios.

• Geomechanics and Engineering
• /
• v.35 no.5
• /
• pp.475-486
• /
• 2023

Ballast particles have an irregular shape and are discrete in nature. Due to the discrete nature of ballast, it exhibits complex mechanical behaviour under loading conditions. The discrete element method (DEM) can model the behaviour of discrete particles under a multitude of loading conditions. DEM is used in this paper to simulate a series of three-dimensional direct shear tests in order to investigate the shear behaviour of railway ballast and its interaction at the microscopic level. Particle flow code in three dimension (PFC3D) models the irregular shape of ballast particles as clump particles. To investigate the influence of particle size distribution (PSD), real PSD of Indian railway ballast specification IRS:GE:1:2004, China high-speed rail (HSR) and French rail specifications are generated. PFC3D built-in linear contact model is used to simulate the interaction of ballast particles under various normal stresses, shearing rate and shear box sizes. The results indicate how shear resistance and volumetric changes in ballast assembly are affected by normal stress, shearing rate, PSD and shear box size. In addition to macroscopic behaviour, DEM represents the microscopic behaviour of ballast particles in the form of particle displacement at different stages of the shearing process.

• Steel and Composite Structures
• /
• v.51 no.1
• /
• pp.53-61
• /
• 2024

Aluminum foams sandwich panel (AFSP) has been used in engineering field, where cyclic loading is used in most of the applications. In this paper, the fatigue life of AFSP prepared by the bonding method was investigated through a three-point bending test. The mathematical statistics method was used to analyze the influence of different plate thicknesses and core densities on the bending fatigue life. The macroscopic fatigue failure modes and damage mechanisms were observed by scanning electron microscopy (SEM). The results indicate that panel thickness and core layer density have a significant influence on the bending fatigue life of AFSP and their dispersion. The damage mechanism of fatigue failure to cells in aluminum foam is that the initial fatigue crack begins the cell wall, the thinnest position of the cell wall or the intersection of the cell wall and the cell ridge, where stress concentrations are more likely to occur. The fatigue failure of aluminum foam core usually starts from the semi-closed unit of the lower layer, and the fatigue crack propagates layer by layer along the direction of the maximum shear stress. The results can provide a reference for the practical engineering design and application of AFSP.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.2
• /
• pp.535-541
• /
• 2020

FCAW is used mainly in the welding of carbon steel and alloy steel because it can be welded in all positions and can obtain excellent quality at sites with variable working conditions. Recently, many studies in Korea have estimated the fatigue strength, residual stress, and deformation, and to develop a fillet welding process. On the other hand, there have been few studies of the mechanical properties based on the strength, macro and magnetic particle test results for fillet welding. This study shows the following results through fillet welding, macro testing and strength testing using SM490A (solid-structure rolled steel) for thick plates using SS400 (rolled steel) for the upper plate and FCAW. The hardness test, macro test and magnetic particle test were then conducted. The hardness tests showed that all result values were smaller than the KS B 0893 standard values of 350Hv. The macro-test showed that each type of welded part was in a normal organic state and that there were no internal errors, bubbles, or impurities on the front of the welded part. Therefore, there were no concerns about lamination. The magnetic particle examination showed no problems.

• Archives of Plastic Surgery
• /
• v.41 no.6
• /
• pp.693-701
• /
• 2014

Background A thin perforator flap is one of the best methods for covering defects. This study aimed to revisit and further test the rapidly advancing field of flap thinning techniques. Methods We performed two cadaveric studies to test the known flap thinning methods, and then applied these methods to a clinical series. In the first study, five cadavers were used to observe the anatomical relation of the perforator with the subdermal plexuses and the subcutaneous fat layer by injecting a colored latex solution. The second study was done on four cadavers independently from the first study. Last, a clinical series was performed on 15 patients. Results The areolar fat lobules of 10 anterolateral thigh perforator (ALT), seven deep inferior epigastric artery perforator (DIEAP), and six thoracodorsal artery perforator (TAP) flaps were dissected to reduce the flap thickness guided by the colored vascular pattern. On average, the ALT, DIEAP, and TAP flaps were reduced to $32.76%{\pm}9.76%$, $37.01%{\pm}9.21%$, and $35.42%{\pm}9.41%$, respectively. In the second study, the areolar fat lobules were directly dissected in six ALT, six TAP, and four MSAP flaps, and an average reduction in flap thickness of $53.41%{\pm}5.64%$, $52.30%{\pm}2.88%$, and $47.87%{\pm}6.41%$, respectively, was found. In the clinical series, 13 out of the 15 cases yielded satisfactory outcomes with an average thickness reduction of $37.91%{\pm}7.15%$. Conclusions These multiple studies showed that the deep fat layer could be safely removed to obtain a thin yet viable perforator flap. This evidence suggests that the macroscopic flap thinning technique can achieve thin flaps. Surgeons should consider this technique before embracing the latest technique of supermicrosurgery.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.3
• /
• pp.80-87
• /
• 2010

The purpose of this paper is to analyze the effects of ethanol blending ratio and fuel temperature in diesel-ethanol blended fuel on the spray-atomization characteristics in a high pressure common-rail injection system. In this work, a diesel fuel and three blended fuels were used as test fuels. Blended fuels were made by blending ethanol with a purity 99.9% to diesel fuel, from 0% to 30%. In order to keep diesel-ethanol blending stability, 5% of biodiesel fuel as volumetric ratio was added into test fuels. The fuel temperature was controled in steps with 40K, from 290K to 370K. Macroscopic spray characteristics were investigated by analyzing the spray tip penetration and spray cone angle through spray images obtained from visualization system. In addition, in order to study microscopic spray characteristics of ethanol blended fuels, the droplet diameter, was analyzed using the droplet measuring system. It is revealed that the spray tip penetration is similar regardless of ethanol blending ratio. As ethanol blending ratio is increased, the spray cone angle becomes wider. It is shown that the spray cone angle is affected by low viscosity and density of ethanol. As the fuel temperature increases, the spray tip penetration and spray cone angle become shorter and narrower respectively. The SMD of ethanol blending fuels is smaller than that of diesel fuel because of low viscosity and surface tension of ethanol.