• Journal of Digital Convergence
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• v.11 no.6
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• pp.73-90
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• 2013

Our basic objective in this paper is to identify a relationship among services, technology level, and service innovation activities using service science approach. The empirical tests are two-fold: first, to find out a difference in the level of service innovations, depending on the service levels and vice versa; second, to investigate the relationship between technology level and service activities and between technology level and service innovation activities. The results of the study are as followed: (1) Service innovation activities are different depending on service activities. (2) Service activities are different depending on service innovation activities. (3) Differences between technology level and service activities and between technology level and service innovation activities do not exist. These findings have implications for both research and practice.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.95-105
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• 2000

Anisotropy of stiffiness, from extremely small strains to post-failure strains, of isotropically consolidated air-pulviated sands in plane strain compression was studied by using the newly developed instrumentation for small strain measurements. Seven types of sand of the world-wide origins were tested, which have been extensively used for research purposes. Stress-strain relationships for a wide range of strain from about 0.0001% to 10% were obtained with measuring axial and lateral strains locally free from the effects of bedding and membrane penetration errors at the specimen boundaries. It was found that the maximum shear modulus Gmax was irrespective of the angle $\delta$of the $\sigma$1 direction relative to the bedding plane. However, the normalized Gmax was varied with the types of sand. Furthermore, the dependency of the strain and stress level on the stiffness increased as decreased.

• Geotechnical Engineering
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• v.14 no.4
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• pp.33-46
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• 1998

Anisotropy of stiffness, from extremely small strains to post-failure strains, of isotropically consolidated air-pluviated sands in plane strain compression was studied by using the newly developed instrumentation for small strain measurements. Seven types of sand of the world-wide origins were tested, which have been extensively used for research purposes. Stress-strain at the specimen boundaries. It was found that the maximum Young's modulus $E_{max}$ was irrespective of the angle $\delta$ of the $\delta_1$ direction relative to the bedding plane. However, the normalized$ E_{max}$ was varied with the types of sand. Furthermore, the dependency of the strain and stress level on the stiffness was increased as $\delta$ decreased.

• Journal of the Ergonomics Society of Korea
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• v.34 no.4
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• pp.335-351
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• 2015

Objective: The aim of this study was to perform a usability test for CPAD (Cognitive Perceptual Assessment for Driving) and improve it based on the test results. Background: The cognitive perceptual assessment for driving is a computer-based assessment tool to assess the driving capacity of people with brain-damages. It may be a good tool for evaluating the brain-damaged drivers' safe driving capabilities and screening cognitive and perceptual deficits related to driving. We performed a usability test to improve the CPAD based on the result. Method: Both the software consisting of 8 sub-tests (depth perception, sustained attention, divided attention, stroop test, field dependency, digit span, trail making A, trail making B) and the hardware including the input and output devices ( joystick, mouse, keyboard, touch screen) were evaluated through user interviews. Also we identified the problems and issues in using them by observing the participants performing the CPAD tasks. Results: Based on the results, the task instructions were visually and auditorily improved and more practice examples were added to help the users understand the instructions better and increase the input accuracy, a response time window was added and the joystick and touch screen were simplified, which made it easier for the user to perform the CAPD tasks. Conclusion: User discomforts were minimized by improving the task environment, unless it had affected the evaluation criteria. Application: We plan to distribute the improved version of the CPAD to the regional rehabilitation hospitals, and the driving support centers for people with disabilities throughout the country, so it could be used as an evaluation tool for disabled drivers' cognitive and perceptual functions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.436-447
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• 2013

In this paper, Integrated circuit(IC) electromagnetic(EM) conducted immunity measurement and simulation using bulk current injection(BCI) and direct power injection(DPI) methods were conducted for 1.8 V I/O buffers. Using the equivalent circuit models developed for IC electromagnetic conducted immunity tests, we investigated the reliability of the frequency region where IC electromagnetic conducted immunity test is performed. The insertion loss for the noise injection path obtained from the simulation indicates that using only one conducted immunity test method cannot provide reliable conducted immunity test for broadband noise. Based on the forward power results, we analyzed the actual amount of EM noise injected to IC. We propose a more reliable immunity test methods for broad band noise.

• Computers and Concrete
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• v.19 no.5
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• pp.579-588
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• 2017

Creep and shrinkage are the main types of volume change with time in concrete. These changes cause deflection, cracking and stresses that affect durability, serviceability, long-term reliability and structural integrity of civil engineering infrastructure. Although laboratory test may be undertaken to determine the deformation properties of concrete, these are time-consuming, often expensive and generally not a practical option. Therefore, relatively simple empirically design code models are relied to predict the creep strain. This paper reviews the accuracy of creep and shrinkage predictions of reinforced concrete (RC) shear walls structures strengthened with carbon fibre reinforced polymer (CFRP) plates, which is characterized by a widthwise varying fibre volume fraction. This review is yielded by three commonly used international "code type" models. The assessed are the: CEB-FIP MC 90 model, ACI 209 model and Bazant & Baweja (B3) model. The time-dependent behavior was investigated to analyze their seismic behavior. In the numerical formulation, the adherents and the adhesives are all modelled as shear wall elements, using the mixed finite element method. Several tests were used to demonstrate the accuracy and effectiveness of the proposed method. Numerical results from the present analysis are presented to illustrate the significance of the time-dependency of the lateral displacements and eigenfrequencies modes.

• Advances in materials Research
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• v.7 no.1
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• pp.45-72
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• 2018

In the present study, a special attention has been paid to the effects regarding the use of different superplasticizers in different dosages. To do so, 36 mixes of normal and self-compacting concrete with two water/binder ratios of 0.35 and 0.45, four different types of superplasticizer including melamine-formaldehyde, naphthalene-formaldehyde, carboxylic-ether and poly-carboxylate, four different superplasticizer/cement ratios of 0.4%, 0.8%, 1.2% and 1.6% and two silica fume/cement ratios of 0% and 10% have been cast. Moreover, the initial and final setting time of the pastes have been tested. For self-compacting mixes, flow time, slump flow, V-funnel, J-ring and L-box tests have been carried out as well as testing the compressive strength and rupture modulus. For normal concrete mixes,slump test has been conducted to assess the workability of the mix and then for each mix, the compressive strength and rupture modulus have been determined. The results indicate that in addition to the important role of superplasticizer type and dosage on fresh state properties of concrete, these parameters as well as the use of silica fume could affect the hardened state properties of the mixes. For instance, the mixes whose superplasticizer were poly-carboxylic-ether based showed better compressive and tensile strength than other mixes. Besides, the air contents showed robust dependency to the type of the superplasticizer. However, the use of silica fume decreased the air contents of the mixes.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.339-345
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• 2012

Information on the deformation behavior and fracture strength of rocks subjected to dynamic loadings is important to stability analyses of underground openings underground vibration due to rock blasts, earthquakes and rock bursts. In this study, Split Hopkinson Pressure Bar (SHPB) system was applied to estimate dynamic compressive and tensile fracture strengths of limestone and also examine deformation behavior of limestones under dynamic loadings. A micro-focus X-ray CT scanner was used to observe non-destructively inside the impacted limestone specimens. From the dynamic tests, it was revealed that the limestone have over 140MPa dynamic compressive strength and the strain-rate dependency of the strength. Dynamic Brazilian tensile strength of the limestone exceeds 21MPa and shows over 3 times static Brazilian tensile strength.

• Explosives and Blasting
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• v.35 no.3
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• pp.15-20
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• 2017

In order to obtain the dynamic response behavior of the rock subjected to blasting loading, a shock-proof high sensitivity impact sensor which can measure high frequency dynamic force and strain events should be adopted. Because the impact sensors which uses quartz and piezoelectric element are costly, generally the strain measurement-based impact (SMI) sensors are applied to high speed loading devices. In this study, dynamic Brazilian tension tests of granitic rocks was conducted using the Nonex Rock Cracker (NRC) reaction driven-high speed loading device which adopts SMI sensors. The dynamic response of the granite specimens were monitored and the intermediate strain rate dependency of Brazilian tensile strengths was discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1831-1843
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• 2001

In this study, convective boiling tests were conducted for enhanced tube bundles. The surface geometry consists of pores and connecting gaps. Tubes with three different pore sizes (d$_{p}$ = 0.20, 0.23 and 0.27 mm) were tested using R-123 and R-l34a for the following range: 8 kg/m$^2$s G 26 kg/m$^2$s, 10 kW/m$^2$ q0 40 kW/m$^2$and 0.1 $\chi$ 0.9. The convective boiling heat transfer coefficients were strongly dependent on heat flux with negligible dependency on mass flux or quality. For the present enhanced geometry (pores and gaps), the convective effect was apparent. The gaps of the present tubes may have served routes for the passage of two-phase mixtures, and enhanced the boiling heat transfer. The convective effect was more pronounced at a higher saturation temperature. More bubbles will be generated at a higher saturation temperature, which will lead to enhanced convective contribution. The pore size where the maximum heat transfer coefficient was obtained was larger for R-l34a (d$_{p}$ = 0.27 mm) compared with that for R-123 (d$_{p}$ = 0.23 mm). This trend was consistent with the previous pool boiling results. For the enhanced tube bundles, the convective effect was more pronounced for R-134a than for R-123. This trend was reversed for the smooth tube bundle. Possible reasoning is provided based on the bubble behavior on the tube wall. Both the modified Chen and the asymptotic model predicted the present data reasonably well. The RMSEs were 14.3% for the modified Chen model and 12.7% for the asymptotic model.model.