• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.174-181
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• 2018

This paper examines the structural behavior of 3D printed concrete specimens with focus on the bond between the layers. The tensile bond and flexural strengths were investigated experimentally and compared with those of specimens made by conventional mold casting. The test parameters were the time gap between printing layers and the reinforcement between vertical layers. The results showed the 3D printed specimens had voids between layers and confirmed the strength reduction due to printing time gap and the stress concentration caused by the voids. Most of the reduction in tensile bond strength between layers was due to the stress concentration at least up to certain printing time gap. Moreover, beyond a certain printing time gap (24hours), the additional reduction in tensile bond strength reached a level that could affect the structural behavior. The reinforcement between layers was helpful to increase the ductile behavior which is essential to prevent the sudden collapse of the structure. In addition, the reduction in flexural strength due to the stress concentration by the voids was observed and should be considered in the design of 3D printed wall structures against the lateral load.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.560-565
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• 2002

In this paper, we implemented the sign board system that displays user's image, user's sentence, the information from DARC an[1 information based position by GPS module for vehicle. The existing sign board is displaying only user's image and sentence. Or other existing sign board is displaying the information via CDMA network. However, our system is also able to display the user's message like other system and gain the information more cheap by DARC. This system consists of 6 parts. The DARC control part classes the DARC information - news, weather, stock and time. The GPS control part gains moment and item to display with calculating the information of global position, direction, speed and satellite. The LED control part has two buffers to store and handle the image. The buffers help the system display various effected images on LED board. An external memory card includes the location based data, the option file and the displayed data files. The data files are stored by FAT 16 with the folder structure on external memory card. The USB controls the communication with PC. PC programs can control and monitor this system. This system is using G72l voice file format, for casting the information. This system was established at the vehicle and we monitored this system. The system displayed the DARC data , user's data and the location based data on the LED board, successfully.

• Steel and Composite Structures
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• v.13 no.3
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• pp.239-258
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• 2012

In this paper, experimental investigations on high strength steel (HSS) stud connected steel-concrete composite (SCC) girders to understand the effect of shear connector density on their flexural behaviour is presented. SCC girder specimens were designed for three different shear capacities (100%, 85%, and 70%), by varying the number of stud connectors in the shear span. Three SCC girder specimens were tested under monotonic/quasi-static loading, while three similar girder specimens were subjected to non-reversal cyclic loading under simply supported end conditions. Details of casting the specimens, experimental set-up, and method of testing, instrumentation for the measurement of deflection, interface-slip and strain are discussed. It is found that SCC girder specimen designed for full shear capacity exhibits interface slip for loads beyond 25% of the ultimate load capacity. Specimens with lesser degree of shear connection show lower values of load at initiation of slip. Very good ductility is exhibited by all the HSS stud connected SCC girder specimens. It is observed that the ultimate moment of resistance as well as ductility gets reduced for HSS stud connected SCC girder with reduction in stud shear connector density. Efficiency factor indicating the effectiveness of high strength stud connectors in resisting interface forces is estimated to be 0.8 from the analysis. Failure mode is primarily flexure with fracturing of stud connectors and characterised by flexural cracking and crushing of concrete at top in the pure bending region. Local buckling in the top flange of steel beam was also observed at the loads near to failure, which is influenced by spacing of studs and top flange thickness of rolled steel section. One of the recommendations is that the ultimate load capacity can be limited to 1.5 times the plastic moment capacity of the section such that the post peak load reduction is kept within limits. Load-deflection behaviour for monotonic tests compared well with the envelope of load-deflection curves for cyclic tests. It is concluded from the experimental investigations that use of HSS studs will reduce their numbers for given loading, which is advantageous in case of long spans. Buckling of top flange of rolled section is observed at failure stage. Provision of lips in the top flange is suggested to avoid this buckling. This is possible in case of longer spans, where normally built-up sections are used.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.117-126
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• 2008

Recent advances in medical imaging technologies have enabled the high-resolution data acquisition. Therefore visualization of such large data set on standard graphics hardware became a popular research theme. Among many visualization techniques, we focused on bricking method which divided the entire volume into smaller bricks and rendered them in order. Since it switches bet\W8n bricks on main memory and bricks on GPU memory on the fly, to achieve better performance, the number of these memory swapping conditions has to be minimized. And, because the original bricking algorithm was designed for regular volume data such as CT and MR, when applying the algorithm to ultrasound volume data which is based on the toroidal coordinate space, it revealed some performance degradation. In some areas near bricks' boundaries, an orthogonal viewing ray intersects the single brick twice, and it consequently makes a single brick memory to be uploaded onto GPU twice in a single frame. To avoid this redundancy, we divided the volume into bricks allowing overlapping between the bricks. In this paper, we suggest the formula to determine an appropriate size of these shared area between the bricks. Using our formula, we could minimize the memory bandwidth. and, at the same time, we could achieve better rendering performance.

• Journal of Korea Game Society
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• v.7 no.4
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• pp.71-80
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• 2007

In this paper, we introduce an efficient GPU-based real-time rendering technique applicable to every kind of game. Our method, without an extra geometry, can represent terrain just with a height map. It makes it possible to freely go around in the air or on the surface, so we can directly apply it to any computer games as well as a virtual reality. Since our method is not based on any geometrical structure, it doesn't need special LOD policy and the precision of geometrical representation and visual quality absolutely depend on the resolution of height map and color map. Moreover, GPU-only technique allows the general CPU to be dedicated to more general work, and as a result, enhances the overall performance of the computer. To date, there have been many researches related to the terrain representation, but most of them rely on CPU or confmed its applications to flight simulation, Improving existing displacement mapping techniques and applying it to our terrain rendering, we completely ruled out the problems, such as cracking, poping etc, which cause in polygon-based techniques, The most important contributions are to efficiently deal with arbitrary LOS(Line Of Sight) and dramatically improve visual quality during walk-through by reconstructing a height field with curved patches. We suggest a simple and useful method for calculating ray-patch intersections. We implemented all these on GPU 100%, and got tens to hundreds of framerates with height maps a variety of resolutions$(256{\times}256\;to\;4096{\times}4096)$.

• Composites Research
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• v.32 no.5
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• pp.284-289
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• 2019

In the present paper, the dynamic force-moment equilibrium equations, driving power and energy equations are analyzed to formulate the equation for fuel economy(km/liter) equivalent to the driving distance (km) divided by the fuel volume (liter) of the vehicle, a selected model of gasoline powered KIA K3 (1.6v). In addition, the effects of the dynamic parameters such as speed of vehicle (V), vehicle total weight(M), rolling resistance ($C_r$) between tires and road surface, inclined angle of road (${\theta}$), as well as the aerodynamic parameters such as drag coefficient ($C_d$) of vehicle, air density(${\rho}$), cross-sectional area (A) of vehicle, wind speed ($V_w$) have been analyzed. And the possibility of alternative materials such as lightweight metal alloys, fiber reinforced plastic composite materials to replace the conventional steel and casting iron materials and to reduce the weight of the vehicle has been investigated by Ashby's material index method. Through studies, the following results were obtained. The most influencing parameters on the fuel economy at high speed zone (100 km/h) were V, the aerodynamic parameters such as $C_d$, A, ${\rho}$, and $C_r$ and M. While at low speed zone (60 km/h), they are, in magnitude order, dynamic parameters such as V, M, $C_r$ and aerodynamic ones such as $C_d$, A, and ${\rho}$, respectively.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.267-284
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• 2004

As an initial step to understand the transitions in Korean bronze technology the present study has examined metallurgical microstructures of 8 artifacts excavated from the Silla Wang-Gyong site in Kyongju. Important trends have been found in alloy compositions and also in manufacturing processes. In the design of alloys, the Sn content was apparently changing toward the peritectic point, 22 mass %, of the Cu-Sn phase diagram while the Pb addition was intentionally avoided. This trend in composition was found accompanied by the introduction, subsequent to casting, of such special thermo-mechanical treatments as quenching and forging in artifact manufacture. In addition, the Sn content in alloys containing a significant amount of As was relatively low and no evidence of forging was observed in them. The use of quenching and forging and the rejection of Pb and As from alloys are all necessary requirements if the brittle nature of high Sn alloys is to be overcome in bronze working. This paper will show that the Wang-Gyong era corresponds to that of innovations leading to the technical climax in Korean bronze tradition, which has been maintained up to the present.

• Conservation Science in Museum
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• v.24
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• pp.17-36
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• 2020

This paper describes the consevation treatment of eleven bigyeokjincheolloe bomb shells that were excavated from the Joseon-period local government office and fortress of Mujang-hyeon (present-day Mujang-myeon) in Gochang in 2018. It also provides information on the production method of the shells revealed through CT scanning, gamma-ray transmission imaging, and metallographic analysis. In preparation for the special exhibition "Bigyeokjincheolloe" at the Jinju National Museum in 2019 (July 16 to August 25), contaminants were removed from the shells and their surface was reinforced during the first phase of conservation treatment. Furthermore, the closures for the shells were identified for the first time. Regarding the production of the shells, the CT scanning and gamma-ray transmission imaging identified many blowholes in the interior of the body and the use of a chaplet on the side of one shell. The side of the body proved to be relatively thinner than the top and bottom. The traces of a hole for pouring molten metal into the center of the bottom indicates that molten metal was indeed emptied into the inverted body. In the metallographic analysis of two of the bodies and one lid, cementite and pearlite structures were identified on the body, indicating that it was made by casting. The presence of the ferrite structure with a partial distribution of the pearlite along with non-metallic inclusion in the lid suggested that the lid was made by forging.

• Korean Journal of Materials Research
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• v.34 no.6
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• pp.291-302
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• 2024

In this paper, iron ore tailings (IOT) were separated from the tailings field and used to prepare cement stabilized macadam (CSM) with porous basalt aggregate. First, the basic properties of the raw materials were studied. Porous basalt was replaced by IOT at ratios of 0, 20 %, 40 %, 60 %, 80 %, and 100 % as fine aggregate to prepare CSM, and the effects of different cement dosage (4 %, 5 %, 6 %) on CSM performance were also investigated. CSM's durability and mechanical performance with ages of 7 d, 28 d, and 90 d were studied with the unconfined compression strength test, splitting tensile strength test, compressive modulus test and freeze-thaw test, respectively. The changes in Ca²⁺ content in CSM of different ages and different IOT ratios were analyzed by the ethylene diamine tetraacetic acid (EDTA) titration method, and the micro-morphology of CSM with different ages and different IOT replaced ratio were observed by scanning electron microscopy (SEM). It was found that with the same cement dosage, the strengths of the IOT-replaced CSM were weaker than that of the porous basalt aggregate at early stage, and the strength was highest at the replaced ratio of 60 %. With a cement dosage of 4 %, the unconfined compressive strength of CSM without IOT was increased by 6.78 % at ages from 28 d to 90 d, while the splitting tensile strength increased by 7.89 %. However, once the IOT replaced ratio reached 100 %, the values increased by about 76.24 % and 17.78 %, which was better than 0 % IOT. The CSM-IOT performed better than the porous basalt CSM at 90 d age. This means IOT can replace porous basalt fine aggregate as a pavement base.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.441-448
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• 2014

From several researches, recently, it was found that using hollowed precast concrete (HPC) column made more compact concrete casting in joint region possible than using normal solid PC (Precast concrete) column. Therefore, the rigidity of joints can be improved like those of monolithic reinforced concrete (RC). After filling the hollow with grout concrete, however, it is expected that the HPC column behaviors like composite structure since PC element and grout concrete have different materials as well as there is a contact surface between two elements. These may affect the structural behavior and strength of the composite column. A compressive strength test was performed for the HPC column with parameter of hollow ratio for the case with and without grout in the hollow and the result is presented in this paper. The hollow ratios in the test are 35, 50 and 59% of whole section of column. Concentrated axial force was applied to top of the specimens supported as pin connection for both ends. In addition, finite element (FE) analysis was performed to simulate the failure behavior of HPC column for axial compression. As a result, it was found that the hollow ratio did not affect the initial stiffness of HPC filled with grout regardless of the strength difference of HPC and grout. However the strength was increased inversely corresponding to the hollow ratio. The structural capacity of HPC without grout closely related to the hollow size. Especially, the local collapse governs the overall failure when the thickness of HPC is too thin. Based on these effect, a suitable equation was suggested for calculation of the compressive strength of HPC column with or without grout. FE analysis considering the contact surface between HPC and grout produced a good result matched to the test result.