• ETRI Journal
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• v.45 no.6
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• pp.1046-1055
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• 2023

We introduce a display for virtual-reality (VR) fire training. Firefighters prefer to wear and operate a real breathing apparatus while experiencing full visual immersion in a VR fire space. Thus, we used a thin head-mounted display (HMD) with a light field and folded optical system, aiming to both minimize the volume for integration in front of the face into a breathing apparatus and maintain adequate visibility, including a wide viewing angle and resolution similar to that of commercial displays. We developed the optical system testing modules and prototypes of the integrated breathing apparatus. Through iterative testing, the thickness of the output optical module in front of the eyes was reduced from 50 mm to 60 mm to less than 20 mm while maintaining a viewing angle of 103°. In addition, the resolution and image quality degradation of the light field in the display was mitigated. Hence, we obtained a display with a structure consistent with the needs of firefighters in the field. In future work, we will conduct user evaluation regarding fire scene reproducibility by combining immersive VR fire training and real firefighting equipment.

• Tribology and Lubricants
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• v.36 no.4
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• pp.244-252
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• 2020

Materials manufactured by powder metallurgy (PM) are widely used in various applications such as water pump, shock absorber, and airplane components due to the reduction in the cost and weight. In this study, tribological properties of carbon steel subjected by surface treatment were investigated. The main purpose is to increase the strength and improve the tribological properties by reducing pores that formed by PM. Moreover, the surface treatment was carried out at room and high temperatures (RT and HT). The surface roughness of the untreated (NON) and treated (AFTER) samples was measured. It was found that the surface roughness was reduced after both the RT AFTER and HT AFTER compared to RT NON sample. The tribological properties of the samples were performed against bearing steel ball under dry conditions. The friction coefficient of the RT NON samples was reduced by 22% and 56% RT AFTER and HT AFTER, respectively. The wear volume of the RT NON sample was also reduced by 43% and 87% RT AFTER and HT AFTER, respectively. Tribocorrosion tests were also performed and it was found that the surface of the RT AFTER, HT AFTER samples was less corroded compared to RT NON sample. The HT AFTER sample demonstrated a relatively higher corrosion potential in comparison with the RT AFTER samples. Hence, it was confirmed that after surface modification the surface roughness and hardness of the samples were significantly improved resulting in improvement in tribological and tribocorrosion behaviors of PM carbon steel.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.71-75
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• 2010

Although Graphite Compacted Vermicular (GCV) was first observed in 1948, the narrow range for stable foundry production precluded the high volume application of GCV to complex components such as cylinder blocks and heads until advanced process control technologies became available. This, in turn, had to await the advent of modern measurement electronics and computer processors. Following the development of foundry techniques and manufacturing solutions, primarily initiated in Europe during the 1990s, the first series production of GCV cylinder blocks began during 1999. Today, more than 40,000 GCV cylinder blocks are produced each month for OEMs, including Audi, DAF, Ford, Hundai, MAN, Mercedes, PSA, Volkswagen, and Volvo. Given that new engine programs are typically intended to support three to four vehicle generations, the chosen engine materials must satisfy current design criteria and also provide the potential for future performance upgrades without changing the overall block architecture. With at least a 75% increase in the ultimate tensile strength, a 40% increase in the elastic modulus, and approximately double the fatigue strength of either iron or aluminum, GCV is ideally suited to meet current and future of engine design and performance requirements.

• The Research Journal of the Costume Culture
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• v.21 no.4
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• pp.596-605
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• 2013

The purpose of this study is to classify and recreate the grooming styles of facial hair sported by noblemen during the Joseon Dynasty. Using existent portraits painted during this period as corroborative materials, this study has identified the traditional grooming styles of facial hair sought by noblemen in this age. This study has utilized 30 facial hair styles found in the portraits of noblemen inherited from the Joseon Dynasty, which take up the majority of the portraits currently remaining in Korea. To recreate grooming styles of facial hair, this study has divided facial hair into three types according to its location: beards, moustaches and whiskers. Based on the analysis of these divided grooming styles, this study has recreated grooming styles of facial hair by using artificial modelling heads, artificial hair, artificial glue, scissors, and a comb. The grooming styles of facial hair recreated by this study are closest to those that noblemen sought and did wear during the Joseon Dynasty. The results of this study are as follows. First, they groomed their moustaches in the 八 shape. Next, they wore their beards in the shape of an inverted triangle. Finally, they also grew and groomed whiskers. Though there are individual differences in the location, length, and volume of facial hair, noblemen in the Joseon Dynasty generally sought to wear their facial hair neat and long. Little research has been done to recreate and present noblemen's grooming styles of facial hair focusing on portraits. Thus, the findings of this study are expected to be utilized as basic materials for the education and research of grooming styles of facial hair according to ages. They can also be used as basic materials for recreating facial hair in historical dramas.

• Tribology and Lubricants
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• v.37 no.5
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• pp.172-178
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• 2021

An injector is a mechanical device present inside the engine. Its main function is to supply an appropriate volume of fuel into the combustion chamber, which is directly related to the overall engine efficiency of a car. During the operation of an injector, a magnetic force lifts the parts of the injector from closed position to open position which generates a horizontal force on the needle. The horizontal force acts on a different position from that of the center of mass of the needle. Therefore, this causes eccentricity in the needle and the generation of a tilting motion during the lifting operation which can result in wear. However, appropriate selection of clearances for these parts can prevent wear. In this study, lubrication analysis is conducted to determine the optimum clearance of parts with sliding motion inside the injector. The height functions are derived considering the dynamic behavior and relative velocity of the parts. Using the derived height function, the pressure profiles are calculated for the lubricated surfaces from the Reynolds' equation. Subsequently, the fluid reaction forces are calculated. The equations of motions are applied to the fluid reaction forces and external forces are solved to calculate the minimum film thickness between each part with variation in the clearances. Finally, the optimum clearances are determined. The effect of the clearances on the behavior of the moving parts is presented and discussed.

• Korean Journal of Human Ecology
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• v.21 no.2
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• pp.299-314
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• 2012

The purpose of this study was to explore effects of pattern alteration using a virtual clothing simulation approach in combination with 3D analysis software. Three raglan sleeves of different patterns were worn by an avatar using virtual clothing simulation with silk and cotton as the test fabrics. It was observed that the silhouette and hemline shape were affected differently based on raglan sleeve pattern and fabric type. By examining clothing pressure distribution, the cotton fabric designs and pattern shapes provided for a variety of influences on armhole and bust regions as well as the back sleeve area. For representative locations, cross section circumstance, cross section area, and volume were measured by using 3D analysis and the resulting correlation between the 2D and 3D data were investigated. Among different fabrics, there was little difference between the 2D and 3D clothing surface area. However, when using 3D analysis, clothing volume was significantly affected by different fabrics and pattern types. By simultaneously adopting the virtual simulator and 3D analysis, quantitative assessment of virtual clothing simulation was successfully conducted. In light of the results of this study, the resulting methodology is expected to be used as a comprehensive evaluation tool for virtual clothing simulation wear testing.

• Composites Research
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• v.14 no.5
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• pp.1-11
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• 2001

The particulates reinforced metal matrix composites(PMMC) have a number of interesting mechanical properties. including high strength and good resistance to wear at high temperature and low thermal expansion. The equipment structure to obtain the homogeneous distribution in composites are proposed for the continuous pouring of reinforcement at the desired temperature. The particulates reinforced metal matrix composites(A357/SiCp) were fabricated by the process of the combined stirring method with the various fabrication process. The combined stirring method to niform distribution of particle is consisted of two stirring force both electro-magnetic stirring generated from induction heating and mechanical stirring with graphite stirrer. PMMC billets were fabricated with the volume fractions ranged from 0% to 20% and particle sizes ranged from 14${\mu}{\textrm}{m}$ to 25${\mu}{\textrm}{m}$. It is important to cont the size of primary $\alpha$-Al solid particles because it could become the cause of the particle pushing or capture phenomena from the fact that secondary dendrite arm spacing size depends on the cooling rate during the solidification in hypoeutectic Al-Si alloy. Therefore, the effect of primary $\alpha$-Al on the reinforcement distribution in matrix alloys has been investigated. The microstructure of PMMC fabracated with various volume fractions(0%, 10%, and 20%) and particle size were observed.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.321-329
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• 2022

Tunnel site where high water pressure is applied, such as subsea tunnel, generally selects the shield TBM (Tunnel Boring Machine) to maintain the tunnel excavation face. The shield TBM has cutters installed, and the cutters wear out during the process of excavation, so it should be checked and replaced regularly. This is called CHI (Cutterhead Intervention). The conventional CHI under high water pressure is very disadvantageous in terms of safety and economics because humans perform work in response to high water pressure and huge water inflow in the chamber. To overcome this disadvantage, this study proposes a new method to dramatically reduce water pressure and water ingress by injecting an appropriate grout solution into the front of the tunnel face through the shield TBM chamber, called New Face Grouting Method (NFGM). The tunnel model tests were performed to determine the characteristics, injection volume, and curing time of grout solution to be applied to the NFGM. Model test apparatus was composed of a pressure soil tank, a model shield TBM, a grout tank, and an air compressor to measure the amount of water inflow into the chamber. The model tests were conducted by changing the injection amount of the grout solution, the curing time after the grout injection, and the water/cement ratio of grout solution. From an economic point of view, the results showed that the injection volume of 1.0 L, curing time of 6 hours, and water/cement ratio of the grout solution between 1.5 and 2.0 are the most economical. It can be concluded that this study has presented a method to economically perform the CHI under the high water pressure.

• Korean Journal of Human Ecology
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• v.7 no.1
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• pp.147-165
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• 1998

The object of this study was to help designing of well-fit and comfortable brassieres for the elementary school girls through the survey on actual condition of wearing brassieres. The subjects of investigation for this study was the elementary school girls in the province of Jeonbuk and Taejeon city. The conclusion of this study was as follows; The 40.2% of the total subjects were wearing brassieres like the 63.3% of the fourth, the 85.4% of the fifth, and the 89.7% of the sixth grade students. The main reason of non wearing brassieres was for the underdeveloped breast, and also that of wearing brassieres was for the good shape of the breast. The main types of brassieres were ranked "Tank Top type", "Mold type", and "Adolescent girl-Bra". They had started to wear brassieres by the recommendation of adults who were their mother or teachers, and usually wearing brassieres all day. They usually purchased brassieres "with mother together" or "only by their mother". The standard of choosing brassieres was also ranked by FASHION, CONVENIENCE, SIZE, TOUCH, and SWEAT ABSORPTION. The total score of satisfaction for wearing brassieres was showed "Average score" and the score higher in Jeonju and Taejeon than in Kunsan. The higher grade and fatter was showed decreasing the score of satisfaction. The higher grade became, the more various for the size and preferable a pure cotton fabric for brassieres. The favorite types of brassieres were "Sport Bra" and "Volume-up Bra". They usually purchased a little larger size than their original size of that.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.9
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• pp.764-775
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• 2002

A kinematic and dynamic optimal design of a new parallel-type rolling mill based upon Stewart platform manipulator is investigated. To provide sufficient degrees-of-freedom in the rolling process and the structural stability of each stand, a parallel manipulator with six legs is considered. The objective of this new parallel-type rolling mill is to permit an integrated control of the strip thickness, strip shape, pair crossing angle, uniform wear of the rolls, and tension of the strip. By splitting the weighted Jacobian matrices Into two parts, the linear velocity, angular velocity, force, and moment transmissivities are analyzed. A manipulability measure, the ratio of the manipulability ellipsoid volume and the condition number of a split Jacobian matrix, is defined. Two kinematic parameters, the radius of the base and the angle between two neighboring Joints, are optimally designed by maximizing the global manipulability measure in the entire workspace. The maximum force needed in the hydraulic actuator is also calculated using the structure determined through the kinematic analysis and the Plucker coordinates. Simulation results are provided.