• Journal of Embryo Transfer
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• v.31 no.3
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• pp.169-177
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• 2016

There is a growing interest in the application of primary hepatocytes for treatment of liver diseases in humans and for drug development. Several studies have focused on long-term survival and di-differentiation blocking of primary hepatocytes in an in vitro culture system. Therefore, the present study also aimed to optimize an in vitro culture system using primary rat hepatocytes. Primary rat hepatocytes from 6-week-old male Crl:CD rats were isolated using a modified two-step collagenase perfusion. Healthy $3.5{\times}10^6$ primary rat hepatocytes were seeded into a 2 dimensional (2D) culture in a 25T culture flask coated with collagen type I or into a 3D culture in a 125-ml spinner flask for 7 days. Production of plasma protein (ALB and TF), apoptosis (BAX and BCL2), and CYP (CYP3A1) related genes were compared between the 2D and 3D culture systems. The 3D culture system had an advantage over the 2D system because of the relatively high expression of ALB and low expression of BAX in the 3D system. However, the level of CYP3A1 did not improve in the 3D culture with and without the presence of a dexamethasone inducer. Therefore, 3D culture has an advantage for albumin production and primary rat hepatocyte survivability, but a low expression of CYP3A1 indicated that primary rat hepatocytes require a high-density culture for stress reduction by continuous flow.

• Tunnel and Underground Space
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• v.24 no.5
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• pp.335-343
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• 2014

Room-and-pillar mining method is one of the most popular underground mining method in the world. If the room-and-pillar mining method is able to be adopted in civil works, it would be highly probable to reduce underground construction costs and to expand a underground structure in use. Therefore, this study aims to analyze the design procedure of unsupported rock pillars which are indispensable to ensure the stability of a room-and-pillar underground structure. Parametric studies on their key design parameters are also carried out for 125 different kinds of design conditions. From the study, the width of a rock pillar is found to show a linear relationship with its corresponding safety factor. The safety factor of a unsupported rock pillar decreased drastically like a negative exponential function as the ratio of room width to pillar width increases in the same rock strength condition. Based on the parametric studies, a design chart to simply evaluate the geometric design parameters of a unsupported rock pillar satisfying a design safety factor is also proposed in this study.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.102-109
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• 2003

The grouted splice steeve has been applied widely due to its superior construction efficiency, such as the unnecessity of post concrete and the large allowable limit to the arrangement of reinforcing bars. However, studies on grout-filled splice steeve still have not been sufficiently peformed. The purpose of this study is to investigate the confining effect of mortar grouted splice sleeve on reinforcing bar, known to strengthen the bond capacity between grout mortar and reinforcing bar. To accomplish this objective, totally 6 full-sized specimens were made and tested under monotonic loading. Each specimens were equipped with strain gauges at the 12 location of sleeve and reinforcing bar. The experimental variables adopted in this study are embedment length and size of reinforcing bars. Following conclusions are obtained; 1) Under ultimate strength condition, the confining pressure of grouted splice sleeve calculated from measured tangential and axial strain of the sleeve is over $200{\sim}300kgf/{cm}^2$ at any location of sleeve and improved with reduction in embedment length of reinforcing bar. 2) Untrauer and Henry's equation which describe bond strength of mortar as a function of its compressive strength and confining pressure, predicted the measured bond capacity of this test within the 5% limits.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.389-397
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• 2010

Concrete has excellent mechanical properties, high durability, and economical advantages over other construction materials. Nevertheless, it is not an easy task to apply concrete to long span bridges. That's because concrete has a low strength to weight ratio. Ultra high performance concrete (UHPC) has a very high strength and hence it allows use of relatively small section for the same design load. Thus UHPC is a promising material to be utilized in the construction of long span bridges. However, there is a possibility of crack generation during the curing process due to the high binder ratio of UHPC and a consequent large amount of hydration heat. In this study, adiabatic temperature rise and mechanical properties were modeled for the stress analysis due to hydration heat. Adiabatic temperature rise curve of UHPC was modeled superposing 2-parameter model and S-shaped function, and the Arrhenius constant was determined using the concept of equivalent time. The results are verified by the mock-up test measuring the temperature development due to the hydration of UHPC. In addition, models for mechanical properties such as elastic modulus, tensile strength and compressive strength were developed based on the test results from conventional load test and ultrasonic pulse velocity measurement.

• Archives of design research
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• v.18 no.4 s.62
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• pp.129-138
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• 2005

Until the early part of the 1990s, interior design has never been thought important by car makers. Repeated attempts have been made to systemize a technical structure, such as layout, driving method, and size, and the car's interior design has been developed by in simple comparison with the exterior design. In the 1990s, however, this trend began to change because consumers began spending more time in their cars, so the motive of the technology development became that of giving comfort and functional satisfaction to the customers. Observing how a person spends inside his or her car and considering the latest trends in car interiors have made a consumer-oriented sense of value i.e., intensifying the personality of the car's interior design and considering the emotional makeup of the consumer factor in the acquisition of a strategic brand identity. These days, car interiors assume a new concept every year due to the constant change in various factors, and the application of a high-tech design, with a sensing function and a navigation system, to achieve driverless running, is being raised as a key trend element technology for the future. Now, at the present when multilateral concept applications of design are attempted under the direct influences from other fields such as product design, fashion and furniture, I would like to lay stress on investigating and analysing the changes in car interior design varying with the background of the times and formative characteristics from the object point of view. On this study, I would like to compare the background of the times and flow of car interior design with priority given to crash pad and would like to attempt to present the direction of the future car interior design together with diversifying major technical factors.

• The Research Journal of the Costume Culture
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• v.14 no.5
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• pp.790-801
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• 2006

This study analyzed features of elements that compose a logo of inner wear brands to get the following results: First, it was found that "elegance" was the most frequently used word to express the concept of inner wear brands to be followed by words like dignity, high-end and aristocratic, words emphasizing femininity, such as feminine, romantic and sexy, words emphasizing practicality, such as convenient, practical, modern, functional and reasonable, and words emphasizing hygiene, such as clean, healthy and hygienic. This suggests that consumers nowadays pursue image more than functional aspects in the shopping of inner wear and consumers' pursuit of such values is reflected in the concept of inner wear brands. Second, unlike logos for outerwear brands that generally used initials of brand name, word-type logos for inner wear brands used the full name of brands, thus suggesting that they put more emphasis on delivery of information rather than on the symbolic aspect. In case of combining characters with concrete objects, they were found generally to use objects that give an soft, elegant and feminine image, such as flowers, woman's head and ribbons. Third, colors in the series of pink and red seemed to be used to convey the concept of inner wear brands that pursue such images as romanticism, femininity, elegance and sensibility, while colors in the series of blue, black and grey for such concepts as functionality, practicality, simplicity, health, hygiene and refinement. With reference to typeface used in the design of logos, unlike outerwear brands of which 83% use sans serif typeface for logos, relatively high percentage of inner wear was found to use typefaces of serif series to stress feminine flexibility and delicacy and give the image of elegance and classical tenderness. With reference to language used in logo naming for inner wear brands, 33 brands were found to use English and only three brands used Korean among the 36 brands surveyed. Even with inner wear brand logos that have Korean name, it was found that they used English in the use of logo marks. Like the result of previous studies, the result of this study indicates that methods to design brand logos for clothing should be incessantly sought in a way to build brand power as an important component to represent concept or function of brands and reinforce brand image.

• Composites Research
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• v.13 no.1
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• pp.1-10
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• 2000

During the compression molding process of the continuous fiber-reinforced polymeric composites, two main problems such as fiber-matrix separation and fiber orientation are produced by the difference of flow velocity. Molded parts are lead to be nonhomogeneous and anisotropic. As the mechanical property of the products are dependent on the separation and orientation, it is important to research the fiber mat structure and molding condition. If the fiber mat structure is changed by the increment of needling, the separation decreases and after compression molding the orientation is easily aligned. As it were, the compression moldability is good. But the defects as tears, thin thickness are produced in the products. Therefore, it is important to clarify the moldability in relation to the usage of products and the expenses of produce on the actual process. Therefore we must make the measurement methods that can define the moldability of products. In this research, the effects of the fiber mat structure(NP = 0, 5, 10, 25, 50 punches/$cm^2$) and the mold geometry($r_p$ = 1, 25, 50 mm) on the moldability of products were discussed. We investigated the case of one-dimensional flow in order to obtain the degree of nonhomogeneity and the fiber orientation function. In result, we could gain the correlation coefficient of the continuous fiber-reinforced polymeric composites. Also we experimented on the cup-type compression molding which was appeared the wrinkle on the flange part by the complex stress condition in order to gain the degree of nonhomogeneity and area ratio. In result, the moldability of products was expressed as the correlation coefficient and area ratio.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.551-558
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• 2011

The effect of the maximum aggregate size and substitution rate of natural sand on the mechanical properties of concrete is evaluated using 15 lightweight aggregate concrete mixes. For mechanical properties of concrete, compressive strength increase with respect to age, tensile resistance, elastic modulus, rupture modulus, and stress-strain relationship were measured. The experimental data were compared with the design equations specified in ACI 318-08, EC2, and/or CEB-FIP code provisions and empirical equations proposed by Slate et al., Yang et al., and Wang et al. The test results showed that compressive strength of lightweight concrete decreased with increase in maximum aggregate size and amount of lightweight fine aggregates. The parameters to predict the compressive strength development could be empirically formulated as a function of specific gravity of coarse aggregates and substitution rate of natural sand. The measured rupture modulus and tensile strength of concrete were commonly less than the prediction values obtained from code provisions or empirical equations, which can be attributed to the tensile resistance of lightweight aggregate concrete being significantly affected by its density as well as compressive strength.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.263-273
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• 2007

Statement of problem: Alteration of tooth function is assumed to be changed by stress/strain on the adjacent alveolar bone, producing changes in morphology similar to those described for other load-bearing bones. When teeth are removed, opposing teeth will not be functioned. When edentulous area is restored by implant prostheses, opposing teeth will be received physiologic mechanical stimuli. Purpose: The aim of this study was to evaluate the bone changes around the teeth opposing implant restoration installed mandibular posterior area. Material and method: Eight patients who had mandibular posterior edentulous area were treated with implants. Radiographs of the opposing teeth were taken at implant prostheses delivery(baseline), 3 months, and 6 months later. Customized film holding device was fabricated to standardize the projection geometry for serial radiographs of opposing teeth. Direct digital image was obtained. Gray values of region of interest at each digital image were measured and compared according to time lapse. Repeated measured analysis of variance and post-hoc Scheffe's test were performed at the 95% significance level. Results: Alveolar bone changes around the natural teeth opposing the posterior implant in mandible showed statistically significant difference compared to control group(P<0.05). And gray values of alveolar bone around the teeth opposing implants were increased. There were no statistically significant differences of alveolar bone changes between crestal group and middle group and between mesial group and distal group according to time lapse(P>0.05). There were no statistically significant differences of alveolar bone changes among mesial-crestal group, mesial-middle group, distal-crestal group, distal-middle group, and control group(P>0.05). Conclusion: Alveolar bone around the natural teeth opposing the implant prosthesis showed gradual bony apposition.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.205-215
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• 2002

This study investigated the compressive fracture strength of Targis ceromer crown by the difference of occlusal thickness on a maxillary first premolar. Control group was a castable IPS-Empress all-ceramic crown with occlusal thickness of 1.5 mm constructed by layered technique. Experimental groups were Targis crowns having different occlusal thicknesses of 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, respectively. The classification of Targis group is T10, T15, T20, T25 and T15N (for no-thermocycling and occlusal thickness of 1.5mm). Ten samples were tested per each group. Except occlusal thickness, all dimension of metal die is same with axial inclination of $10^{\circ}$and marginal width 0.8mm chamfer. All crowns were cemented with Panavia F and thermocycled 1,000 times between $5^{\circ}$ and $55^{\circ}$ water bath with 10 sec dwelling time and 10 sec resting time. The compressive fracture strength was measured by universal testing machine. The results were as follows : 1. Fracture strength was increased as the occlusal thickness increased : compressive fracture strength of Group T10, T15, T20, T25 was $66.65{\pm}4.88kgf$, $75.04{\pm}3.01kgf$, $87.07{\pm}7.06kgf$ and $105.03{\pm}10.56kgf$, respectively. 2. When comparing material, Targis crown had higher fracture strength than IPS-Empress crown : the mean compressive strength of group T15 was $75.04{\pm}3.01kgf$ and the value of group Control was $37.66{\pm}4.28kgf$. 3. Fracture strength was decreased by thermocycling : the compressive fracture strength of T15 was $75.04{\pm}3.01kgf$, which is lower than $90.69{\pm}6.88kgf$ of group T15N. 4. The fracture line of crowns began at the loading point and extended along long axis of tooth. IPS-Empress showed adhesive failure pattern whereas Targis had adhesive and cohesive failure. In the SEM view, stress was distributed radially from loading point and the crack line was more prominent on Targis crown.