• Tunnel and Underground Space
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• v.28 no.6
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• pp.555-568
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• 2018

To perform efficient and safe haulage operations in mines, the condition of unsurfaced roads where dump trucks are moving should be regularly investigated, and systematic maintenance should be carried out according to the results. In this study, we developed a smartphone application that can be used to periodically investigate the unsurfaced road conditions in mines. Using the developed application, necessary data can be easily collected on site to evaluate the condition of unsurfaced roads according to the Unsurfaced Road Condition Index (URCI) evaluation system presented by the US Army Corps of Engineers. The smartphone application was tested at several sections of unsurfaced road in the Ilkwang mine, Busan, Korea. The results showed that the field investigation about 7 factors considered in the URCI evaluation system can be conducted through the user interface screen, and the URCI value can be calculated in the field to evaluate the condition of unsurfaced road. The smartphone application developed in this study can be useful for surveying and evaluating the unsurfaced road conditions at the mine site.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.1-12
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• 2015

PURPOSES : This paper presents a description of the current issues facing road managers regarding the surface-type conversion of low-volume roads for cost savings. METHODS: The paper reviews previous works conducted toward this end, acknowledges gaps in the current research, and lays out what information is needed for further studies. RESULTS : If the cost to maintain an unsurfaced road is less than the cost of maintaining a surfaced road, then there is potential for cost savings for the management agency. However, the problem is bigger than simply maintaining the roads that already exist. If unsurfaced roads prove to be more economical than surfaced roads, then the cost to convert from a surfaced to an unsurfaced roadway, and vice versa, when necessary, must also be examined. CONCLUSIONS : No other studies have addressed the un-surfacing of a road for cost savings, and it is therefore unknown whether substantial savings can be realistically obtained by converting from a surfaced to an unsurfaced road. To determine whether a conversion policy would be a viable option, additional data and research are needed.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.4
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• pp.300-305
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• 2020

Purpose: The purpose of this study is to compare the shear bond strength of 3D printing denture base resin according to surface treatment of artificial teeth. Materials and methods: 3D printing denture base resin was fabricated as specimens using 3D printer. The experimental group divided the surface treatment of artificial teeth into five groups according to the application of sandblasting and primer (n=10). Shear bond strengths between denture base and artificial teeth were measured by universal testing machine. All measurements were analyzed by one-way ANOVA and Turkey test (α=.05). Fracture mode of each specimen was analyzed. Microscopic evaluation was conducted by using a scanning electron microscope. Results: Unsurfaced treated group represented the lowest value. The primer groups had significantly higher result values (P<.05). Most specimens of the primer groups had cohesive failure. Conclusion: In 3D printing denture base resin group, mechanical and chemical surface treatment of artificial teeth has increased the shear bond strength. Therefore, if dentures are produced using 3D printing, proper mechanical and chemical treatment of artificial teeth is necessary for adhesion of dentures and artificial teeth.