• Journal of Biomedical Engineering Research
• /
• v.38 no.1
• /
• pp.9-15
• /
• 2017

Recently, flexible cages have been introduced in an attempt to absorb and reduce the abnormal load transfer along the anterior parts of the spine. They are designed to be used with the pedicle screw systems to allow some mobility at the index level while containing ROM at the adjacent level. In this study, a finite element (FE) study was performed to assess biomechanical efficacies of the flexible cage when combined with pedicle screws with flexible rods. The post-operated models were constructed by modifying the L4-5 of a previously-validated 3-D FE model of the intact lumbar spine (L2-S1): (1) Type 1, flexible cage only; (2) Type 2, pedicle screws with flexible rods; (3) Type 3, interbody fusion cage plus pedicle screws with rigid rods; (4) Type 4, interbody fusion cage plus Type 2; (5) Type 5, Type 1 plus Type 2. Flexion/extension of 10 Nm with a compressive follower load of 400N was applied. As compared to the Type 3 (62~65%) and Type 4 (59~62%), Type 5 (53~55%) was able to limit the motion at the operated level effectively, despite moderate reduction at the adjacent level. It was also able to shift the load back to the anterior portions of the spine thus relieving excessively high posterior load transfer and to reduce stress on the endplate by absorbing the load with its flexible shape design features. The likelihood of component failure of flexble cage remained less than 30% regardless of loading conditions when combined with pedicle screws with flexible rods. Our study demonstrated that flexible cages when combined with posterior dynamic system may help reduce subsidence of cage and degeneration process at the adjacent levels while effectively providing stability at the operated level.

• Journal of the Korean Society of Costume
• /
• v.65 no.3
• /
• pp.151-166
• /
• 2015

This research aims to study the needs of the trail runners as trail running has become a popular outdoor activity, and give suggestions for high functional outdoor menswear design that can satisfy the needs of the highly demanding taste of runners. The design development is as follows: 1) The design had to be made of lightweight material and be easily packable in all situations, and 2) we also considered the ergonomic and compact fit for activity, 3) the functional location of high functional fabric, 4) the reflective use and layering system giving a wide range of outdoor workout time and 5) the trend in 2016 S/S active sports and outdoor wear. Based on the above elements, the men's outdoor wear design has been developed for trail running in spring and summer. The design development includes a total of 7 items. The design focused on lightweight, availability of packaging, "comfortability" and freshness in activity, functional suitability of location of highly functional materials and the layering system to protect body temperature under the changing environment. In particular, the layering system was implemented to provide ventilation, and it was done in body parts that released the most body heat. Therefore, mesh materials were actively used on the side panel, sleeves and center of the back piece for necessary sweat emission without any problems and ventilation for trail running.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.6
• /
• pp.42-49
• /
• 2007

In this study, we analyzed flow characteristics of micro-nozzles for basic research to develop micro propulsion system. Cold gas propulsion system was used, and micro-nozzles having nozzle throat diameters of 1.0, 0.5, 0.25 mm were fabricated with EDM method. Thrust was measured through the use of plate-spring and strain gage based thrust measurement system, and flow characteristics of micro-nozzles were analyzed under ambient condition and vacuum condition. We used argon and nitrogen gases as propellant, and compared experimental results with CFD analysis. From the result, we verified the flow losses of viscosity and back-pressure caused by minimization of nozzle.

• Korean Journal of Clinical Laboratory Science
• /
• v.37 no.2
• /
• pp.118-122
• /
• 2005

An epidemiological study was performed on zoophilic dermatophytes. The number of patients with zoophilic dermatophytes diagnosed on clinical findings and culture at the Catholic Dermatological Clinic in Daegu City were 1,339 for 10 years from January 1995 to December 2004. Species of zoophilic dermatophytes isolated from 47,925 patients with dermatophytes were as follows; Trichophyton(T.) rubrum was isolated from 43,702 (91.2%), T. interdigitale 2,660 (5.6%), Epidermophyton(E.) floccosum 43 (0.1%), T. tonsurans 131 (0.3%), T. mentagrophytes 625 (1.3%), T. verrucosum 56 (0.2%), Microsporum(M.) canis 658 (1.4%), and M. gypseum 50 (0.1%). Zoophilic dermatophytes infections were chiefly Tinea facial in the cases of T. mentagrphytes and Tinea corporis in the cases of T. verrucosum, but Tinea capitis in the cases of M. canis. Number of patients with zoophilic dermatophytes by site and age were as follows; Most patients with infected scalps were young people under 15 years old. Infection of the trunk area (neck,chest,back) and extremities (arms, legs, hands, feet) were relatively high in those patients over 15 years old. M. canis were most frequently isolated in autumn and winter, and T. mentagrophyts and T. verrucosum were mostly in spring and winter.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.7 no.3
• /
• pp.75-80
• /
• 2008

The progressive die performs a work of sheet metal processes with a piercing, notching, embossing, bending, drawing, cut-off etc. in many kinds of pressing. Now a days, these processes have been evaluated as a advanced tooling method to increase the productivity and high quality assurance. The first step analyzing of die design is production part review, then the arrangement drawing of product design and strip process layout design should be done as a next steps with a FEM simulation for its problem solution. After upper procedure were peformed, it was started to make the die, then tryout and its revision of the die and product quality, safety, productivity etc. were done continually. For the all of these process, we mobilized the theory and practice of sheet metal forming, die structure, the function and activity of die components, and the others of die machining, die material, heat treatment and know‐how so on. In this study the features of representative are production part analyzing through the FEM simulation of bending area with a considering spring back problem by DEFORM.

• Journal of the Korean Society for Heat Treatment
• /
• v.21 no.2
• /
• pp.87-93
• /
• 2008

A variety of minor alloying elements such as Zr, Sr, Y, and Gd were added to Mg-3%Zn-0.5%Sn base alloy to form various fine precipitates and their effects on the microstructure, tensile properties, and sheet metal formability were investigated. Various very fine precipitates along with fine second phases were observed by the additions. It was found that Zr or Gd additive has a role to suppress the grain coarsening of alloy sheets during the hot working process. The Zr-added alloy showed the highest tensile elongation at $250^{\circ}C$ whereas the Gd-added alloy exhibited the best sheet metal forming characteristics in terms of CCV (conical cup value) and spring-back tendency.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.8 no.2
• /
• pp.60-68
• /
• 2009

The objective of this paper is to design stamping die of inner reinforcement panel with DL 950 advanced high strength steel as stamping materials through numerical analyses and experiments. The stamping process was designed as bending dominant process consisting of 1 step of notching and 4 steps of bending processes. In order to obtain a proper design of the stamping die, various three-dimensional elasto-plastic finite element analyses were performed using a commercial code AUTOFORM V4.2. Design parameter of stamping die was chosen as the corner radius of the stamping die for each step. From the results of the FE analysis, feasible corner radii of the stamping die, which can minimize the deviation of corner angle of the stamped part from design data, and forming load for each part were estimated. Stamping experiments were carried out using the manufactured stamping die according to the proposed die design. The results of experiments were shown that the stamping die can successfully manufacture the inner reinforcement panel with DL 950 advanced high strength steel as base stamping material.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.321-325
• /
• 2005

Bipolar plate is the main part with MEA in automotive PEMFC. It must have a good electrical conductivity and excellent corrosion resistance, be cost effective. Therefore, stainless steels have been studied by many researchers because of its corrosion resistance and cost benefits. But their properties are not sufficient for the application to bipolar plate for automotive PEMFC. In this work, we have performed stamping using various commercial stainless steels to select candidate material for biploar plate and to derive design parameters for stamping simulation. The results showed that a small curvature at the corner of flow field is more favorable due to easier a plastic deformation. Stamping process was simulated by changing surface condition, and the size and angle of channel. The optimum shape and spring back phenomena were evaluated. Surface coating was applied to increase the corrosion resistance and electrical conductivity of stainless steel. The electrical interfacial resistance was 10 to $15m{\Omega}cm^2$ under clamping force of 150psi. But corrosion resistance of coating on the stainless steel was not good due to the unstableness of microstructure.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.8
• /
• pp.96-103
• /
• 2009

The roll forming process is commonly used for the conventional 'Fe' metal products such as a furniture drawer guide or an up-down slide guide. Recently its applications are variously expanded to the sanitary facilities or electronic devices. It is essentially required the cleanness for the high technology application and any corrosion or rust are not allowed. Therefore, in those applications the stainless steel materials are strongly demanded as the substitution of 'Fe' steel. However the mechanical properties of stainless steel are not suitable for forming process compared with those of 'Fe' steel. Up to now, the conventional F.E.M.(Finite Element Method) has been used to analyze and design the roll forming process. The purpose of this research is to obtain the proper production process and the shape of rolls to manufacture the high precision slide rails made of stainless steel material. The commercial program, SHARPE-RF, is used to analyze the entire roll forming process. The results show that the rolling process and the roll design by F.E.M. are useful from the good agreement between the shapes of products estimated by F.E.M. and those of the actual products.

• Transactions of Materials Processing
• /
• v.20 no.2
• /
• pp.110-117
• /
• 2011

The purpose of this work is to develop of a press forming process for mobile phone battery cover as an alternative to the current manufacturing process by laser welding. This press forming process consists of a combination of bending, side pressing and side bending operations. The dimensional error for each process was investigated by finite element(FE) analysis and the Taguchi optimization method. The spreading of the cover width in the side pressing process was adjusted by modifying the blank shape with a notch. The over-bending method was adopted to compensate the spring-back which occurs after bending. Forming experiments were performed to verify the reliability of the developed press forming process. In addition, the strength of the product was evaluated to verify the suitability of the battery cover manufactured with this new press forming process. The results of the forming experiments indicate that the dimensional accuracy of the battery cover is within the required tolerance. The strength of the battery cover was evaluated to 547N which is larger than required strength of 400N.