• Proceedings of the KIEE Conference
• /
• 2003.11c
• /
• pp.612-615
• /
• 2003

In this paper, a design of radiation detector for gamma column scanner is introduced. Distillation column is important unit in Petro-chemical industries, and its on-line diagnose is very important. To get density profile measured by the radiation transmitted through column is well method for on-line diagnose as gamma scanning. For this purpose radiation detection circuit, radiation source and mechanical system for moving source and detector are required. Conventional radiation detection circuit for this application is sensitive to electric noise because of interface between the radiation circuit and the controller for mechanical system. The radiation detection system introduced here is using loop coil instead of slip ring to remove contact noise. Radiation detection system designed here for gamma scanning consist of BGO detector, high voltage circuit, PHA circuit and FSK modem. The BGO detector is used as radiation sensor, high voltage circuit and peak height analysis circuit is essential to process the signal generated from BGO detector. Micro controller convert measured data into ASCII data. FSK modem transmit ASCII data. Transmitted ASCH data is picked up in antenna coil and processed for combined function with mechanical system. This method gives good result by isolating the controlling circuit of mechanical system from radiation detecting circuit which is sensitive to noise.

• Journal of the Korean Society of Mechanical Technology
• /
• v.13 no.2
• /
• pp.93-100
• /
• 2011

This study deals with the high frequency induction hardening (HF at $850^{\circ}C$, 120kHz & 50kW condition) SM45C steel. (1) The HF specimen, which was tempered at $150^{\circ}C$, did not show any tempering effect. A brittle fracture occurred at rounded area of the tensile specimen. AE (acoustic emission) amplitude distribution showed between 45dB and 60dB. (2) A slip and fracture occurred at the hole area of the HF specimen which was tempered at $300^{\circ}C$. As they pass the yield point, the AE energy is increased intermittently and AE amplitude distribution exists between 70dB and 85dB. In addition, after imposing the maximum tensile load, AE signals showed high amplitude and energy distribution. The AE amplitude showed between 45dB and 70dB. (3) A brittle fracture occurred at HF specimen which was tempered at $450^{\circ}C$ as if it is torn in the direction of $45^{\circ}$ on parallel area over the both sides of the tensile specimen, which lead to several peak appeared in AE energy. It was found that the AE amplitude was relatively low and the AE energy was high.

• Structural Engineering and Mechanics
• /
• v.76 no.6
• /
• pp.823-837
• /
• 2020

In this research, the idea of improving the seismic response of an existing steel structure with use of friction dampers between external walls and the structure is discussed. The main difference of this method with other methods of seismic rehabilitation is that interior spaces of the existing structure remain untouched and new parts including external walls and dampers are added outside of the structure. Three frames having 3, 6 and 9 stories are modeled in SAP2000 software before and after seismic retrofit and responses of the system are investigated under the effect of seven earthquake records. Initially, different ratios of seismic weight of stories are presumed for slip forces of the dampers with a distribution based on given equations. The optimized capacity of dampers is obtained by investigating the average of maximum displacement, acceleration and base shear of the structure caused by earthquakes. For this optimized values, maximum inter-story drifts and acceleration are obtained through numerical models. Results show that in 3, 6 and 9-story frames peak roof displacement decreased up to 80%. Maximum roof acceleration and base shear of the frames also decreased 46, 40 and 32% and 84, 67 and 65%, respectively for three building structures.

• Steel and Composite Structures
• /
• v.44 no.6
• /
• pp.803-816
• /
• 2022

Composite materials are effective in forming externally bonded reinforcements which find applications related to existing structures repair, attributed to their high strength-to-weight ratio and ease of installation. Among various composites, fibre reinforced polymers (FRP) have somewhat been largely accepted as a commonly utilized composite for such purposes. It is only recently that steel fibres have been considered as additional members of the FRP fibre family, intuitively termed as steel reinforced polymer (SRP). Owing to its low cost and permissibility of fibre bending at sharp corners, SRP is rapidly becoming a viable contender to other FRP systems. This paper investigates the bond behaviour of SRP-concrete joints with different bonded lengths (50, 75, 100, 150 and 300 mm) and widths (15, 30, 40, 50, and 75 mm) using single-lap shear tests. The experimental specimens contain SRP strips with a fixed density of steel fibres (0.472 cords/mm) bonded to the face of concrete prisms. The load responses were obtained and compared in terms of corresponding load and slip boundaries of the constant region and the peak loads. The failure modes of SRP composites are discussed, and the range of effective bonded length is evaluated herein. In the end, a new analytical model was proposed to estimate the SRP-concrete bond strength using a genetic algorithm, which outperforms 22 existing FRP-concrete bond strength models.

• Korean Journal of Materials Research
• /
• v.2 no.6
• /
• pp.389-397
• /
• 1992

Workability and aging behavior of Mg-Li-Al alloys hate been investigated with variation of Li and Al contents. It was found that ${\alpha}$(HCP) + ${\beta}$(BCC) two phase structure reveals better workability than ${\alpha}$(HCP) single phase structure. Increase of workability is attributed to the additional slip on pyramidal and prism planes besides the slip on basal plane of HCP Mg. Workability of ${\alpha}$+${\beta}$ two phase structure is improved with increased amount of Al. Among alloys studied in the present study, reduction limit up to 62 % was obtained for Mg-8.08Li-4.26Al. MgL$i_2$Al(${\theta}$) aging precipitation was observed in ${\alpha}$+ ${\beta}$ two phase structure, while it was not in a single phase structure. Result of microhardness reveals peak hardness for ${\alpha}$ +${\beta}$ two phase structure due to $\theta$ precipitate in ${\theta}$ phase. In ${\alpha}$+${\beta}$ two phase Mg-Li-Al alloys, hardness increased with increasing amount of Al. It is believed that addition of Al raised the amount Al partition in u phase and ${\theta}$ precipitation in ${\beta}$ phase.

• The Korean Journal of Rheology
• /
• v.11 no.1
• /
• pp.57-65
• /
• 1999

In order to measure yield stress of PIM feedstocks simply and effectively, a yield stress measuring technique was developed by a vane method. The vane method had an advantage that there was no wall-slip, while it had a drawback that it could not measure viscosity change at various shear rates. A Newtonian fluid was tested for the appropriateness of the measuring technique. The end effect of a vane was checked to produce an acceptable error. The torque peak has been considered to be developed at yielding of non-Newtonian fluids with yield stress. However, it was influenced very much by control system of the instrument so that the torque value at the stable region was taken to calculate yield stress. Torque at zero rotational speed was obtained by extrapolating the torque values at various speeds to remove the effect of the rotational drag. As general verification, yield stress of feedstocks made of Tungsten carbide powder with wax-based binder was measured at different temperatures and various powder concentrations.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.12 no.1
• /
• pp.62-71
• /
• 1990

This study was to evaluate the nature of traumatic injuries on anterior teeth of 530 patients and the prognosis of stabilized cases of 102 patients, including possible 18-follow up cases among them, treated at Dental Hospital, Yonsei Medical Center from Mar. 1983 to Feb. 1988. The obtained results were as follows. 1. The peak of monthly distribution of trauma to the anteriors was June and was the lowest in November. The ratio of male to female was 2.6 : 1. The most common incidence of the trauma to the anteriors was seen in the 3rd decades. The most chiefly involved teeth were central incisors in both upper and lower jaws. The causes of trauma were as followed in descending order by first blows, traffic accidents, falls, slip downs, and sports. The types of traumatic injuries of anterior teeth consisted of periodontal tissue injuries(55.9%), the injuries to the hard dental tissues and pulp(31.3%), and alveolar bone injuries(12.8%). 2. 35.1% stabilized anteriors were treated with root canal therapy. The success rate of stabilization was 95.3%, and 92.3% in replantation of avulsed teeth. 3. External root resorption, internal root resorption with calcification of pulp chamber or root canal, ankylosis of root, and other periapical pathosis were seen in follow-up radiographic findings. 4. Success rate of stabilization of the traumatized anteriors after 3 years showed 71.4% average.

• Computers and Concrete
• /
• v.22 no.4
• /
• pp.395-405
• /
• 2018

In this paper, the performance of post-installed adhesive bonded anchor embedded in concrete is assessed using numerical simulations. This study aims at studying the influence of parameters on the performance of a chemically bonded anchorage system. Non-linear finite element modelling and simulations are carried out by properly using the material properties and phenomenon. Materials parameters such as characteristic length, fracture energy, damage criteria, tension retention and crack width of concrete and interface characteristics are carefully assigned so as to obtain a most realistic behaviour of the chemical anchor system. The peak strength of two different anchor systems obtained from present numerical studies is validated against experimental results. Furthermore, validated numerical models are used to study the load transferring mechanism and damage progression characteristics of various anchors systems where strength of concrete, strength of epoxy, and geometry and disposition of anchors are the parameters. The process of development of strain in concrete adjacent to the anchor and energy dissipated during the course of damage progression are analysed. Results show that the performance of the considered anchorage system is, though a combined effect of material and geometric parameters, but a clear distinction could be made on the parameters to achieve a desired performance based on strength, slip, strain development or dissipated energy. Inspite the increase in anchor capacity with increase in concrete strength, it brings some undesirable performance as well. Furthermore, the pullout capacity of the chemical anchor system increases with a decrease in disparity among the strength of concrete and epoxy.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.24 no.3
• /
• pp.345-351
• /
• 2016

This study was carried out to determine an optimal lean $NO_x$ trap (LNT) regeneration condition based on a $NO_x$ storage fraction. The LNT regeneration was performed by an in-cylinder post fuel injection method. A $NO_x$ storage fraction is defined by the ratio of current cumulated $NO_x$ amount in the LNT to the $NO_x$ storage capacity: 0 means empty and 1 fully loaded. In this study five engine operating conditions were chosen to represent the New European Driving Cycle. With various $NO_x$ storage fractions each engine operating condition, the LNT regeneration was executed and then $NO_x$ conversion efficiency, additional fuel consumption, CO and THC slip, peak catalyst temperature were measured. The results showed that there exist an optimal condition to regenerate the LNT, eg. 1500 rpm 6 bar BMEP with below 0.7 $NO_x$ storage fraction in this experimental constraint.

• Journal of Trauma and Injury
• /
• v.22 no.1
• /
• pp.87-96
• /
• 2009

Purpose: Injuries are the most important cause of morbidity and mortality in the childhood population worldwide. Thus, this study was down to investigate the type and the severity of injuries according to the age group in childhood. Methods: A survey of injury information and a chart review were done on 378 children (257 boys, 121 girls) who visited the Emergency Departments of Asan Medical Center from March 1, 2009, to March 31, 2009. To determine differences in injury mechanism, accident place, injury site, New Injury Severity Score (NISS) and Pediatric Trauma Score (PTS), we divided the 378 patients into 4 group: under 1 year, 1 to 4 years, 5 to 9 years, and 10 to 15 years. Results: The mean (${\pm}SD$) age of the study group was 5.1 (${\pm}4.4$) years. Two year olds formed the largest group of injured children, with 77 cases (20.4% of the total). The most common cause of injury in childhood was being hit by an object (26.2%). Falls were frequent in the under-1-year group (22.2%) and slip downs (30.1%) were more frequent in 1-to-4-year group. More than half (53.4%) of the injuries occurred in the home, and the most common places of home-related injuries were the living room (41.1%) and the bedroom (31.2%). The mean (${\pm}SD$) NISS was 1.5 (${\pm}1.8$), and traffic accidents had the highest NISS ($2.8{\pm}5.1$). Injuries occurred most frequently during the evening. The peak period was 4:00 PM to 8:00 PM (33.7%). Conclusion: Patterns of childhood injury by age group were considerably different, and less severe and nonhospitalized injuries were common. Thus, need to improve surveillance of a variety of injuries, promote intersectional collaboration, build institutional capacities and mobilize community support and policy as an investment in prevention.