• Earthquakes and Structures
• /
• 제10권2호
• /
• pp.313-328
• /
• 2016

Beam-column joints are recognized as one of the most critical and vulnerable zones of a Reinforced Concrete (RC) moment resisting structure subjected to seismic loads. The performance of the deficient beam-column joints can be improved by retrofitting these joints by jacketing them with varied materials like concrete, steel, FRP and ferrocement. In the present study strength behavior of RCC exterior beam-column joints, initially loaded to a prefixed percentage of the ultimate load, and retrofitted using ferrocement jacketing using two different wrapping schemes has been studied and presented. In retrofitting scheme, RS-I, wire mesh is provided in L shape at top and at bottom of the beam-column joint, whereas, in scheme RS-II along with wire mesh in L shape at top and bottom wire mesh is also provided diagonally to the joint. The results of these retrofitted beam-column joints have been compared with those of the controlled joint specimens. The results show an improvement in the ultimate load carrying capacity and yield load of the retrofitted specimens. However, no improvement in the ductility and energy absorption has been observed.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2001년도 추계학술대회 논문집
• /
• pp.228-232
• /
• 2001

Fatigue strength, electrical conductivity and stress-corrosion-cracking resistance are considered as important factors at aircraft Al alloys, therefore Al7050 alloy has been developed to improve such properties. However, hammer-forged Al7050 parts showed the undesirable structures such as severe local grain coarsening and inhomogeneous material flow, resulted in the degraded mechanical properties. In this paper, process conditions are investigated for elimination of the grain coarsening and improved material flow during forging process by both of experiments and FEM analysis. Particular interest has been given to understand role of preform shape on the grain coarsening behavior and magnitude of the hammer forging load The use of preform has been beneficial for reduction of the forging load and elimination of the grain coarsening. However, in the cases of as received bar and the round bar, which was machined to 2.5mm thickness in surface layer, some degree of local grain coarsening behavior has been observed. The optimized preform shape could be properly designed by applying the FEM simulation.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제38권
• /
• pp.37.1-37.5
• /
• 2016

Background: The dimensions and shape of the forehead determine the esthetics of the upper third of the face. Korean young people consider a broad and smooth, rounded forehead more attractive. As a result, frontal augmentation becomes more popular in patients with dentofacial deformities. Various surgical procedures and materials have been used in frontal augmentation surgery, with associated advantages and disadvantages. Silicone is a good candidate for frontal augmentation. The author presents two cases of esthetic frontal augmentation with a prefabricated silicone implant in female patients with dentofacial deformities. Case presentation: In case 1, a 24-year-old female patient underwent frontal augmentation surgery with simultaneous maxillomandibular and zygomatic osteotomies to correct facial asymmetry. A silicone implant was fabricated preoperatively using a positive template stone mold of her forehead. In case 2, a 23-year-old female patient underwent total facial contouring surgery including frontal augmentation for improved facial esthetics. A computed tomography (CT)-guided rapid prototype (RP) model was used to make the silicone implants. The operative procedure was safe and simple, and the silicone implants were reliable for a larger degree of frontal augmentation. Six months later, both patients had recovered from the surgery and were satisfied with their frontal shape and projection. Conclusions: Frontal augmentation with silicone implants can be an effective adjuvant strategy to improve facial esthetics in patients with a flat and narrow forehead who undergo orthognathic reconstruction or total facial contouring surgery.

• 한국공간구조학회논문집
• /
• 제14권4호
• /
• pp.55-64
• /
• 2014

In this study, Intersecting Tensegrity System that is integrated solid compression members with tension members was presented. This system is set up by connecting upper and lower compression members of pyramid shape with exterior tension members. In this system, the solid compression members are intersected each other and connected by a tension member in the center. This system is a variation of Tensegrity system, has a improved feature that the system is able to induce prestresses in all of tension members easily by adjusting the distance of a tension member in the center. The proposed system was studied by modeling, and the structural behavior of the system was investigated by mechanical analysis of the model. Furthermore, the features of the structural behavior variations was investigated when the composition elements(total height, size of surface, intersection length, etc.) are changed variously. It was also showed that the system is able to be used as a temporary space structure system with a membrane roof of inverse conical shape.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.1276-1279
• /
• 2007

The main objectives of the Load/Unload are no slider-disk contact and no media damage. But, it remains unsolved technical problems on the unloading process. While the slider climbs up the ramp at the outer edge of the disk, the possibility of the slider-disk contact by lift-off force and rebound of the slider increases. Keeping in mind of these points, to prevent the slider-disk contact, we apply the disk bump on disk outer edge proceeding unload. First, referring to the simulation results, we select the optimal bump shapes to improve unload performance by unload analysis. Second, the disk bump is mechanically manufactured by pressing disk surface using tungsten tips. The bumps are variously processed by changing pressing pressure of tungsten tips. After confirming bump shape by nano-scanner, the optimal bump shape is applied to experimental unload process. Through this experiment, it is conformed that the unload performance was improved by using the optimal disk bump to prevent the slider-disk contact.

• 대한기계학회논문집A
• /
• 제28권9호
• /
• pp.1314-1319
• /
• 2004

In this study, parameter optimization of micro-static mixer with a cantilever beam was accomplished for maximizing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.

• 대한의용생체공학회:의공학회지
• /
• 제19권6호
• /
• pp.563-570
• /
• 1998

The purpose of this study was to investigate the effects of scintillator and collimator parameters that tradeoff between system sensitivity and spatial resolution. The parameters simulated using Monte Carlo program were scintillator thickness, colimator hole shape, septal thickness, and hole length. The results show that the sensitivity increases exponentially upto about 1 cm of scintillator thickness as the thickness increases. However the sensitivity is almost constant when the scintiallator is thicker than about 1 cm. The simulation of collimator hole shape shows that the hexagonal hole gives the best spatial resolution for the same system sensitivity. The system statical resolution is improved, as both collimator septal thickness and hole length increase, however that system sensitivity is rapidly decreased. In conclusion, The optimization of scintillator and collimator parameters using monte carlo simulation may be useful to develop a high-resolution miniature gamma probe.

• 한국자동차공학회논문집
• /
• 제16권4호
• /
• pp.88-96
• /
• 2008

Effects of the duct inlet guide vane on the flowrate distribution characteristics of the defroster nozzle exit in a defrost duct system were investigated experimentally to design the optimum heating, ventilation and air conditioning (HVAC) system applied in an automotive compartment. A 3-dimensional hot-wire anemometer system was used to measure the velocity field in the vicinity of the defroster nozzle jet flow and the velocity distributions near the windshield interior surface. At first, two cases of with- and without-duct inlet guide vanes were considered as the test condition, and then three cases of the duct inlet guide vane were tested to determine the optimum guide vane shape and their positions. The arrangement of the duct inlet guide vanes has an effect on the improved flowrate distribution at the defroster nozzle exit and near the windshield interior surface. However, the application of the lots of guide vane to control the flow direction leads to increase the flow resistance, resulting in the decreased flowrate issuing from the defroster nozzle. The shape of the duct inlet guide vane affects not only the flowrate distribution between the driver side and the assistant driver side but also the reduction of the flow resistance in the defrost duct system.

• Structural Engineering and Mechanics
• /
• 제67권6호
• /
• pp.555-563
• /
• 2018

Architectural fabrics membranes have not only the structural performance but also act as an efficient cladding to cover large areas. Because of the direct relationship between form and force distribution in tension membrane structures, form-finding procedure is an important issue. Ideally, once the optimal form is found, a uniform pre-stressing is applied to the fabric which takes the form of a minimal surface. The force density method is one of the most efficient computational form-finding techniques to solve the initial equilibrium equations. In this method, the force density ratios of the borders to the membrane is the main parameter for shape-finding. In fact, the shape is evolved and improved with the help of the stress state that is combined with the desired boundary conditions. This paper is evaluated the optimum amount of this ratio considering the curvature of the flexible boarders for structural configurations, i.e., hypar and conic membranes. Results of this study can be used (in the absence of the guidelines) for the fast and optimal design of fabric structures.

• 소성∙가공
• /
• 제15권4호
• /
• pp.304-310
• /
• 2006

Due to a recent growth of the area of MEMS and a trend moving toward smaller scale, a micro manufacturing that is usually related with lithography is now emerging. Differently from traditional manufacturing processes, the micro or miniature manufacturing usually requires expensive sophisticated equipments and its characteristics are of high cost and of low productivity. However, a miniature stamping, which makes small sized product with a thin metal usually in the range of meso-scale, can be realized in a low cost and in a high productivity with relatively inexpensive equipments. For a successful development of miniature stamping, lots of obstacles, including material properties related with formability, have to be overcome. Since the thin metal shows distinctive characteristics, e.g., size effect and statistically scattered material properties, the formability of miniature stamping is not good in general and the possible shape with the miniature stamping is limited relatively simple shapes. Since the optimal blank improves formability and the improved formability can make up for problems of material properties, the possibility of success can be increased. This study is carried out to show the possibility of miniature stamping and to verify the effect of optimal blank for the miniature stamping.