• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.100-100
• /
• 2009

This paper is concerned with numerical analyses of residual stresses in welds and material's susceptibility to stress corrosion cracking (SCC) for the primary piping system in nuclear power plants: Both the dissimilar metal weld (DMW) for stainless steel to low alloy steel joints and the similar metal weld (SMW) for forged stainless steel to cast stainless steel joints are considered. Thermal elasto-plastic analyses using the finite element method (FEM) are performed to predict residual stresses generated in fabrication welding and its related processes for both the DMW and SMW, including effects of quenching for cast stainless steel piping, machining of the DMW root, and grinding of the SMW root. As a result, the effect of quenching should be included in the evaluation of residual stresses in the SMW for the cast stainless steel piping. It is deemed that residual stresses in both the DMW and SMW would not affect the SCC susceptibility of the welds providing that the welding processes are completed without any weld repair on the inside wall of the joint. However, the grinding process if performed on the safe-end to piping weld, would produce a high level of residual stresses in the inner surface region and thus a stress improvement process (e.g. buffing) should be considered to reduce susceptibilities to SCC.

• Journal of Korean Society of Forest Science
• /
• v.86 no.1
• /
• pp.80-86
• /
• 1997

The objective of this study was to investigate how resistant poplar hybrid makes compensation to ozone stress. Growth, net assimilation rate and initial Rubisco activity were investigated. This study elucidates the physiological mechanisms associated with ozone sensitivity and resistance in 3 selected $F_2$ hybrids, a family originating from a cross between Populus trichocarpa${\times}$P. deltoides. Open-top chambers were used. Ozone concentrations varied from 90 to 115 ppb for 126 days, 6 to 9 hours in a day. This study tested the hypothesis that resistant poplar hybrid maintains the biomass production to ozone exposure via increased net assimilation rate and Rubisco activity. Growth, biomass, net assimilation rate and initial Rubisco activity were generally reduced by ozone treatment. In the tree parts, root under ozone stress was the most sensitive part. Reduced allocation of photosynthates to root growth might be due to increased respiratory demands for maintenance and repair of aboveground tissue damaged by ozone stress. Maintenance or increases remaining leaves in photosynthetic rates and Rubisco activity in resistant clone in response to ozone treatment were the results of biological compensation to ozone stress.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.6
• /
• pp.704-711
• /
• 2023

This paper discusses the control method of BLDC(Brushless Direct Current) motor that has similar electrical characteristics with DC motor but has improved its lifespan and reliability. The BLDC motor can improve durability and speed stability by using rotor position information to eliminate commutators that require mechanical contact with DC motors. In this study, a controller for a DC motor was designed based on the fact that the current in the windings of a BLDC motor is a square-wave current like the current flowing in the armature of a DC motor. Next, the designed controller was applied to a 3-phase BLDC motor to confirm the effectiveness of the controller. In detail, a single-phase DC motor with electrical parameter values of a three-phase BLDC motor was modeled and a PI controller for motor speed control was designed by applying the root locus method to the derived system. The speed control simulation of the DC motor was performed to confirm the validity of the controller, and the same controller was applied to the speed control of the 3-phase BLDC motor implemented in MATLAB. From the simulation, similar results of the DC motor were obtained in the 3 phase BLDC motor and confirmed the usefulness of the proposed control scheme.

• The Journal of the Korean dental association
• /
• v.50 no.3
• /
• pp.148-154
• /
• 2012

Mineral trioxide aggregate (MTA) is mainly composed of lime and silica. Its four major phases are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracaclcium aluminoferrite. MTA has relatively long initial setting time (2h 45m) and various additives can be added to reduce setting time. Compressive strength of MTA increases with time and reaches 100 MPa after 28 days. MTA has high pH of 9-12.5 because of the formation of calcium hydroxide during its hydration reaction. MTA has superior sealing ability to amalgam and IRM when it is used in perforation repair or root end filling. MTA is safe in cytotoxicity and genotoxicity and have potential to promote pulpal and periapical hard tissue formation.

• Archives of Plastic Surgery
• /
• v.35 no.3
• /
• pp.273-278
• /
• 2008

Purpose: The most widely accepted protocol for alveolar cleft reconstruction is to repair it during the mixed dentition stage. There were lower resorption rate (about 88%) at this stage. However we found some cases that need repeated bone grafting. Therefore we sought to analyze the cause of repeated alveolar bone grafting in connection with other factors. Methods: From January 2000 to January 2006, thirty-nine secondary alveolar bone grafts with iliac crest spongiosa were carried out. In 39 patients, 5 patients who had significant bone graft resorption received repeated alveolar bone graft. In all the cases, the causes of repeated bone grafts were dental root exposure(angulation), and the deficiency of the bony support for lateral incisor or canine eruption. In 3 cases, there was deficiency of the alveolar bone at the cleft side. There was the need of repeated bone grafts for orthodontic treatment in 2 cases and for application of dental implants in 1 case. Results: During the follow-up period, the clinical and radiologic examinations showed that repeated alveolar bone grafts were maintained successfully without any complications. The volume of the repeated bone graft was sufficient for orthodontic treatment and implantation. Conclusion: The essential conditions for successful alveolar bone grafting includes the status of cleft sided teeth, further treatment and planed schedule, as well as canine eruption. Alveolar bone grafting has to be performed with difference of each case in mind.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.44 no.3
• /
• pp.296-301
• /
• 1999

The concerns on the crop damage by ultraviolet (UV) radiations is increasing owing to the decrease of their absorbing stratospheric ozone in the tropospheric. Cultivar differences on early growth of UV radiation among five Korean rice cultivars, four japonica types and one Tongil type (indica-japonica cross hybrid), were studied. Pot-seeded rice plants were grown under four different radiation conditions, i.e., visible radiation only, visible radiation with supplemented with high or low dose of UV-B (280~320 nm in wavelength) and UV-C (less than 280 nm in wavelength). The inhibitory degree on plant height, shoot and root weight and length of leaf blade and leaf sheath were determined at 40 days after seeding. UV-C showed the most severe inhibitory effect on the degree of biomass gain and leaf growth in most cultivars examined, followed by high UV-B and low UV-B. Among the cultivars used, the Kuemobyeo was the most sensitive cultivar and had not repair or showed resistance ability to continued irradiation of UV radiation. However, Janganbyeo and Jaekeon showed different responses that the elongation of leaf blades was promoted on 2nd and 3rd leaves and inhibited on 4th and 5th leaves but this inhibitory degree was reduced on 6 th and 7th leaves. Such tendency on leaf growth means that both cultivars had low sensitivity and most resistant ability to continued irradiation of UV radiation. While Tongil showed different response to enhanced UV radiation, ie., low UV-B promoted leaf growth but the inhibitory was severely increased by continued irradiation of high UV-B and UV-C, which means that Tongil had high threshold of UV radiation for response as an inhibitory light of plant growth. The results of this study indicate that the differences on sensitivity or resistant to the effects of UV radiation were existed among Korean rice cultivars.

• Advances in biomechanics and applications
• /
• v.1 no.3
• /
• pp.169-185
• /
• 2014

Computational multibody models of the elbow can provide a versatile tool to study joint mechanics, cartilage loading, ligament function and the effects of joint trauma and orthopaedic repair. An efficiently developed computational model can assist surgeons and other investigators in the design and evaluation of treatments for elbow injuries, and contribute to improvements in patient care. The purpose of this study was to develop an anatomically correct elbow joint model and validate the model against experimental data. The elbow model was constrained by multiple bundles of non-linear ligaments, three-dimensional deformable contacts between articulating geometries, and applied external loads. The developed anatomical computational models of the joint can then be incorporated into neuro-musculoskeletal models within a multibody framework. In the approach presented here, volume images of two cadaver elbows were generated by computed tomography (CT) and one elbow by magnetic resonance imaging (MRI) to construct the three-dimensional bone geometries for the model. The ligaments and triceps tendon were represented with non-linear spring-damper elements as a function of stiffness, ligament length and ligament zero-load length. Articular cartilage was represented as uniform thickness solids that allowed prediction of compliant contact forces. As a final step, the subject specific model was validated by comparing predicted kinematics and triceps tendon forces to experimentally obtained data of the identically loaded cadaver elbow. The maximum root mean square (RMS) error between the predicted and measured kinematics during the complete testing cycle was 4.9 mm medial-lateral translational of the radius relative to the humerus (for Specimen 2 in this study) and 5.30 internal-external rotation of the radius relative to the humerus (for Specimen 3 in this study). The maximum RMS error for triceps tendon force was 7.6 N (for Specimen 3).

• Korean Journal of Environment and Ecology
• /
• v.18 no.4
• /
• pp.437-445
• /
• 2004

The purpose of this study was to provide basic visitor and trail use data for developing trail management strategies in Korean national park system. To accomplish the purpose of the study, a questionnaire survey was carried on at two different national parks(Bukhansan and Chiaksan National Park). As for the results, root and rock exposure on the trails and trail width expansion were perceived as major types of trail impact. In addition, majority of respondents pointed to construct or maintain facilities on steep paths and repair trail surface as for the priority of trail maintenance. In conclusion, the priority of trail management and maintenance has to be differently determined based on each trail conditions because visitor impacts on the trails vary along with site-specific and activity-specific differences. Findings of the study expect to be used as fundamentals in trail management strategy making for Korean national parks.

• Journal of Chest Surgery
• /
• v.34 no.9
• /
• pp.724-728
• /
• 2001

We report a case of an 8 years and 11 month-old male patient who had developed severe tricuspid insufficiency(TI) after correction of anomalous origin of the left coronary artery from the pulmonary artery(ALCAPA). Transthoracic echocardiogram and coronary angiography confirmed ALCAPA, ischemic mitral regurgitation and trivial TI. He underwent direct reimplantation of the left coronary artery to the aortic root by using additional cannulation at the main pulmonary artery for arterial inflow and cardioplegia delivery to the left coronary artery. After the correction of ALCAPA, transesophageal echocardiogram(TEE) revealed good antegrade flow at the aortic implantation site of the left coronary artery and severe TI(Gr III-IV/IV). Cardiopulmonary bypass was reestablished and tricuspid valve was repaired with Kay-type annuloplasty, artificial chordae formation and chordal shortening plasty. The postrepair TEE revealed trivial to mild TI.

• Journal of Chest Surgery
• /
• v.40 no.3 s.272
• /
• pp.225-227
• /
• 2007

The aortic inclusion technique is frequently used in the original Bentall's procedure for the control of excessive postoperative bleeding. Although this procedure has improved the outcome of patients with aortic root disease, there is a high incidence of both early and late complications, including coronary artery stenosis, kinking or pseudoaneurysm formation at the coronary suture lines. Pseudoaneurysm of the ascending aorta is a relatively rare, but fatal complication, which occurs after wrap-inclusion composite graft replacement. Herein, the case of a 45-year-old female, who developed a perigraft aortic pseudoaneurysm 10 years after a Bentall's procedure (wrap-inclusion technique), but was successfully managed using the Cabrol's method, is reported.