• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.86-91
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• 2008

The rubber was compounded with carbon black and silica series-filler to examine the effects of the various rubber fillers on a gasket material's suitability and fuel cell stack conclusion. The evaluation of a long term heat resistance and oil resistance of the mixed rubber material was performed considering at the drive environment of PEMFC. Test results of compression set for the most influencing property of gasket showed that it was about less than 15% at long term of up to 1000 h. In this experiment, FEM analysis is carried out about the rubber material's properties depending on each filler and the stress which is produced when a gasket is contracted by using various filler. Sealing force was expected to maximum 2.5 MPa from minimum 0.2 MPa by using FEM (finite element method) at stacking gasket to gasket.

• Korean journal of food and cookery science
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• v.13 no.4
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• pp.390-395
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• 1997

The inhibitory effects of cereal extracts and concentrates from barley, waxy rice flours and malt on enzymatic browning were measured using apple polyphenol oxidase (PPO). Malt concentrate showed the largest inhibitory effect on PPO among all. The relationship between the properties of malt concentrate such as browning intensity and reducing power and their inhibitory effect on PPO was also studied. As the heating time increased, the browning intensity and the reducing power of malt concentrates were increased, while PPO activities were decreased. Inhibitory effect of malt concentrates on PPO increased with heating time and their concentration. L-value and compression force of the apple slices dipped in malt concentrate decreased by 6.9% and 14.3%, respectively, showing the smallest changes compared with raw and water-dipped apple slices during cold storage for 9 days. These results suggest that malt concentrate can be a potential source for the control of enzymatic browning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5B
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• pp.437-442
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• 2011

As an Internet Engineering Task Force (IETF) Working Group, 6LoWPAN is standardizing the IPv6 packet transfer technology in accordance with IEEE 802.15.4. It has completed two Request for Comments (RFC) documents, one of which, RFC 4944, addresses fragmentation, reassembly, and header compression technologies. In this paper, a communication mechanism is proposed to provide efficient communication between 6LoWPAN and external nodes. In this mechanism, the gateway between 6LoWPAN and external networks serves as the proxy gateway between nodes. The simulation was conducted using QualNet to compare the performance of the proposed mechanism and the existing RFC 4944 method. The comparative analysis of the proposed mechanism and the existing method showed that the proposed method performed better.

• The Journal of Korean Physical Therapy
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• v.17 no.4
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• pp.457-467
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• 2005

Physiotherapyists frequently use manipulative therapy technique to treat dysfunctionand pain resulting from ankle sprain. Despite the high prevalence of lateral ankle ligament injuries, few studies are available indicating any physical associations with the development of lateral ankle ligament injuries, or information of treatment for lateral ankle ligament injuries. To investigate the effect of passive joint mobilization, the anteroposterior glide on the talus, on increasing weight-bearing dorsiflexion, single support time and VAS. Sixty lateral ankle ligament injuries (grade I and grade II) aged between 17 and 27 years (mean age 21) were recruited. Subjects were randomly assigned to 1 of 2 treatment groups. The control group received a protocol of rest, ice, compression, and elevation (RICE) and massage. The experimental group received the anteroposterior mobilization, using a force that avoided incurring any increase in pain, in addition to the RICE protocol. Subjects in both groups were treated every second day for a maximum of 2 weeks or until the discharge criteria were met, and all subjects were given a home program of continued RICE application. Outcomes were measured after each treatment. The results showed that the experimental group than the control group. Weight-bearing dorsiflexion (F=7.640, P<0.05), single support time (F=85.532, P<0.05) and VAS (F=10.610, P<0.050). Between-groups differences were observed as; experimental group is increased weight-bearing dorsiflexion, single support time and reduced VAS.

• Magazine of the Korea Concrete Institute
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• v.5 no.2
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• pp.181-188
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• 1993

In this study, a numerical method for the material nonlinear analysis of reinforced concrete shell structures including the time dependent effects due to creep and shrinkage is developed. Degenerate shell elements with the layered approach are used. The perfect or strain hardening plasticity model in compression and the linearly elastic model in tension until cracking for concrete are employed. The reinforcing bars are considered as a steel layer of equivalent thickness. Each :steel layer has an uniaxial behaviour resisting only the axial force in the bar direction. A bilinear idealization is adopted to model elasto-plastic stress-strain relationships. For the nonlinear anaysis, incremental load method combined with unbalanced load iterations for each load increment is used. To include time dependent effects of concrete, time domain is divided into several time steps which may have different length. Some numerical examples are presented to study the validity and applicability of the present method. The results are compared with experimental and numerical results obtained by other investigator.

• Tribology and Lubricants
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• v.31 no.5
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• pp.221-228
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• 2015

It is possible to prevent a piston from contacting the cylinder by changing the shape of the piston or by applying micro-textures, such as micro-grooves or micro-holes, over the piston surface. Usually, the minimum radial clearance reaches its minimum value at the beginning of the suction stroke because the pressure around the piston is low and almost axisymmetric such that the net pressure force on the piston is not sufficiently high to support the piston from touching the cylinder. In this study, we apply a series of saw-tooth-shaped grooves on the piston surface, and numerically investigate the effects of groove depth, groove angle, and the number of grooves with radial clearance variations using a finite difference method. We conduct a dynamic analysis of the piston for various changes in groove geometries to obtain the minimum radial clearance variation for the entire compression cycle. The minimum radial clearance increases while friction loss decreases when we apply the series of saw-tooth-shaped grooves on the piston. In addition, we analyze the impact of the change in the groove shape variable due to changes in radial clearance. Leakage variations are relevant to radial clearance, but have almost no effect on the groove parameters.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.8-16
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• 2015

Prestressed concrete (PSC) is a method in which prestressed tendon is placed inside and/or outside the reinforced concrete member and the compressive force applied to the concrete in advance to enhance the engineering properties of concrete member which is weak under tension. In this paper we suggested the precast PSC girder assembled with segments of portable size and weight at the factory. The segments of precast PSC girder will be delivered and assembled as a unit of PSC girder at the site. Consequently, we suggested new-type of precast segmented PSC girder with different shapes of segment cross-section (i.e., I-shape, Box-shape). To mitigate the problems associated with the field splice between the segments of precast PSC girder anchor system is attached near the neutral axis of the girder and relatively uniform compression throughout the girder cross-section is applied. Prior to the experimental investigation, analytical investigation on the structural behavior of precast PSC girder was performed and the serviceability (deflection) and safety (strength) of the girder were confirmed. In addition, 4-point bending test on the girder was conducted to investigate the structural performance under bending. From the experimental investigation, it was found that the precast PSC girder spliced with 3 and 5 segments has sufficient in serviceability and safety conditions and it was also observed that the point where the segments spliced has no defects and the girder behaves as a unit.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.683-690
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• 2020

The objective of this study was to analyze time-dependent changes in bite marks on pig skin. Bite marks produced by the average bite force of adults were analyzed three-dimensionally for 3 hours directly after its formation, at 1-hour intervals. The measured values were calculated by root mean square (RMS) and statistically analyzed by one-way ANOVA test (α = 0.05). The average bite sizes were 0.899 mm, 0.717 mm and 0.506 mm at the first, second and third intervals, respectively, and were significantly different between the three intervals (P < 0.05). A bite mark showed time-dependent changes in the compression level, showing the greatest change in the first interval. Changes in bite marks decreased over time, and bite marks were observed most prominently generated by the anterior dentition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.747-756
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• 2016

In this paper, a connection details for precast arch structures was proposed. Experiments were performed to evaluate structural performance of the loop connection details satisfying current design requirements and of alternative details for improvement of constructability. Precast arch specimens considering the current design requirements showed higher structural capacity than a cast-in-place arch specimen. Crack width at the connection of arch crown showed smaller value than 0.2 mm due to increased compression force by the applied vertical load. Strengthening by wire-mesh at notch area of the connection improved initial crack control capability. Connection detail with couplers and headed bars showed similar capacity to the reference specimen. The alternative details to improve constructability of reinforcements can be used without decreasing structural performance. Specimens with smaller internal diameter of mandrel and shorter loop splicing than the current design codes showed worse behavior in terms of crack width control.

• The korean journal of orthodontics
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• v.21 no.1 s.33
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• pp.77-96
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• 1991

Many studies has been conducted concerning prevention of unnecessary complications such as root resorption during orthodontic too th movement under various mechanical forces. Nowadays, the cause of the root resorption is not thought to be confined only to mechanical forces. But the factor that affects bone metabolism are thought to be major one of the predisposing factors. The light microscope and scanning electron microscope were used to the effects of 60 gm, and 100 gm of tipping force on root resorption of cats, which were treated with Etidronate disodium. The results were as follows: 1. In the 60gm control group, hyalinization on the compression site of periodontal ligament appeared after first week and second week. In the 60gm experimental group, it appeared after first week with low frequency. In the 100gm control group it appeared with high frequency by first and second week while in 100gm experimental group, it appeared with low frequency. 2 In the 100gm control group, resorption of the cementum and the alveolar bone rapidly increased after second week. In the 60gm experimental group, resorption or formation of alveolar bone and cementum didn't appear all through the experimental period. 3. In the 100gm control group, formation of cementum and alveolar bone appeared after first week while in the 100gm experimental group, formation of cementum and alveolar bone appeared after second week and fourth week respectively. In the 60gm control group, formation of the cementum didn't appear all through the experimental period. 4. In the control group, the root resolution of 100gm group was higher than that of 60gm group after second week, while in experimental group, root resorption didn't appear regardless of the forces.