• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.17-24
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• 2011

The characteristics of flow and strength of CLSM depend on the combination ratio including the fly ash, pond ash, cement, water quantity and etc. However, it is very difficult to draw the mechanism about the flow, strength and the mixing ratio of each components. Therefore, the method of calculation drawing the flow about the component ratio of CLSM and compression strength value is needed for the valid practical use of CLSM. To verify the efficiency of artificial neural network, new data which were not used for establishing the model were predicted and compared with the results of laboratory tests. In this research, it was used to evaluate the learning efficiency of the artificial neural network model and the prediction ability by changing the node number of hidden layer, learning rate, momentum, target system error and hidden layer. By using the results, the optimized artificial neural network model which is suitable for a flow and compressive strength estimate of CLSM was determined.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.661-671
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• 2018

Domestic studies on steel plate concrete structures have focused on nuclear structures with high strength. In this study, the SC structure was applied to the general structure, and the SC structure that is advantageous in terms of safety and construction was limited to a special structure. As a basic study for applying SC, this paper proposes basic design information of a SC structure applying cement concrete to plan the structure, which is suitable for eco - friendliness by replacing concrete cement, an important factor in a SC structure, with blast furnace slag. This study examined the compression characteristics and the effective length factor under central compression load. To calculate the effective length factor, the Euler column theory was applied without applying plate theory. The effective length factor was calculated from the yield strength of the steel plate, buckling of the steel plate, and the point at which the concrete was broken. In addition, this study examined whether the maximum compressive strength meets the national and international reference equations with the slenderness ratio (B/t) as a parameter. By analyzing the buckling of the specimen by applying the column theory and selecting the strain of the measured steel plate, the effective length factor was analyzed and compared with the value presented in the reference equation.

• The Korean Journal of Emergency Medical Services
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• v.11 no.2
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• pp.51-66
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• 2007

Purpose: With a view to providing basic data to develop cardiopulmonary resuscitation education suitable for elementary students, the cardiopulmonary resuscitation education was conducted to grasp students' knowledge, skills accuracy and the attitude change before and after the education. Methods: Convenience sampling was made on fourth and fifth graders(total-35 students) of S elementary school located in K city, Chungcheongnam-do, and this was a pre-experiment research designed before and after choosing a single group. In terms of methods, specifically we, researchers ; 1) Handed out questionnaires to students directly to make them fill in firsthand and collected the questionnaires. 2) Utilized PPT materials based on 2005 AHA guideline and DVD materials of AHA, to give students theoretical education of cardiopulmonary resuscitation. We used Anne/SkillReporter$^{(R)}$ torso produced by Leardal Inc, and Little Anne to conduct practical education individually. 3) Asked students to give Anne/SkillReporter$^{(R)}$ torso cardiopulmonary resuscitation five times with the ratio of 30 : 2, and then one of researchers filled in the evaluation sheet individually. 4) Evaluated the accuracy of students' ability to perform the resuscitation based on the record of Anne/SkillReporter$^{(R)}$ integrated printer(which was the objective tool to grasp students' skills accuracy). 5) Gave out questionnaires to make students fill them in and then collected them. after completing the practical evaluation. Results: 1) In case of the attitude about cardiopulmonary resuscitation, Students' confidency rose from 19.28%(before the education) to 93.57(after the education)- which is a positive change. 2) As the result of the education, some elementary students scored 11 points (full score-16 points), up from 5 points before the education, in terms of the knowledge about cardiopulmonary resuscitation. The average point also reached 13.14 points(after the education), jump from 8.37(before the education), which was the rise of 29.8%. 3) When it comes to the practical performance, the skills accuracy was 80.93% on average, and the calculation method was as follows: total items were 16, and each item was marked form 0 to 2 points, meaning the full score was 32 points. The minimum score was 19 points and the maximum was 32($M{\pm}SD=25.90{\pm}2.88$), which was calculated based on percentage. 4) Regarding skills accuracy, respiration accuracy(%)($M{\pm}SD=30.20{\pm}27.16$) was higher than pressure accuracy(%) ($M{\pm}SD=15.34{\pm}25.27$). Conclusion: The result showed that students' attitude on cardiopulmonary resuscitation changed positively. and meaningful difference(p = .00) existed in the change of students' knowledge. In terms of skills accuracy. chest compression and airway control showed high accuracy, but the result of Anne/SkillReporter$^{(R)}$ performance showed that the accuracy of chest compression was lower than that of mouth-to-mouth resuscitation.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.45-53
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• 2022

In order to improve the emission of diesel engines, natural gas-diesel dual fuel combustion compression ignition engines are in the spotlight. In particular, a reactivity controlled compression ignition (RCCI) combustion strategy is investigated comprehensively due to its possibility to improve both efficiency and emissions. With advanced diesel direct injection timing earlier than TDC, it achieves spontaneous reaction with overall lean mixture from a homogeneous mixture in the entire cylinder area, reducing nitrogen oxides (NOx) and particulate matter (PM) and improving braking heat efficiency at the same time. However, there is a disadvantage in that the amount of incomplete combustion increases in a low load region with a relatively small amount of fuel-air. To solve this, sensitive control according to the diesel injection timing and fuel ratio is required. In this study, experiments were conducted to improve efficiency and exhaust emissions of the natural gas-diesel dual fuel engine at low load, and evaluate combustion stability according to the diesel injection timing at the operation point for power generation. A 6 L-class commercial diesel engine was used for the experiment which was conducted under a 50% load range (~50 kW) at 1,800 rpm. Two injectors with different spray patterns were applied to the experiment, and the fraction of natural gas and diesel injection timing were selected as main parameters. Based on the experimental results, it was confirmed that the brake thermal efficiency increased by up to 1.3%p in the modified injector with the narrow-angle injection added. In addition, the spray pattern of the modified injector was suitable for premixed combustion, increasing operable range in consideration of combustion instability, torque reduction, and emissions level under Tier-V level (0.4 g/kWh for NOx).

• Journal of the Korean GEO-environmental Society
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• v.11 no.6
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• pp.85-91
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• 2010

As enormous construction projects of land development are carried out around Korea, useful construction materials are needed to perform the construction projects. However, there are no more enough of fill and reclamation materials in our country. That is why the coal ash is expected to be utilized as an alternative material. Since the coal ash has the characteristics of a pozzolan and a selfhardening material, it is adjudged that coal ash has a great possibility to be used as a fill and reclamation material. In this study, grain size analysis, Atterberg limit test, and specific gravity test were performed to examine the physical characteristics of the coal ash about a self-hardening material before utilizing the coal ash in the construction. Compaction test, unconfined compression test, direct shear test, and flexible wall permeability test were conducted to investigate the engineering characteristics according to mixture ratios of fly ash and bottom ash. As a result of the tests, it was confirmed that the mixing ratio 1:1 of fly ash and bottom ash is the most effective to use as a fill and reclamation material. If the mixture of coal ash is used as a backfill material with light weight around structure, it is expected to play a significant role in reducing earth pressure on the back of the structure. As the age of the mixture of coal ash goes by, it intends to decrease the coefficient of permeability. As described above, the coal ash should be considered as an alternative material of fill and reclamation materials since the result of the tests indicates that the coal ash is suitable to a useful material on the construction design.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.441-448
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• 2014

From several researches, recently, it was found that using hollowed precast concrete (HPC) column made more compact concrete casting in joint region possible than using normal solid PC (Precast concrete) column. Therefore, the rigidity of joints can be improved like those of monolithic reinforced concrete (RC). After filling the hollow with grout concrete, however, it is expected that the HPC column behaviors like composite structure since PC element and grout concrete have different materials as well as there is a contact surface between two elements. These may affect the structural behavior and strength of the composite column. A compressive strength test was performed for the HPC column with parameter of hollow ratio for the case with and without grout in the hollow and the result is presented in this paper. The hollow ratios in the test are 35, 50 and 59% of whole section of column. Concentrated axial force was applied to top of the specimens supported as pin connection for both ends. In addition, finite element (FE) analysis was performed to simulate the failure behavior of HPC column for axial compression. As a result, it was found that the hollow ratio did not affect the initial stiffness of HPC filled with grout regardless of the strength difference of HPC and grout. However the strength was increased inversely corresponding to the hollow ratio. The structural capacity of HPC without grout closely related to the hollow size. Especially, the local collapse governs the overall failure when the thickness of HPC is too thin. Based on these effect, a suitable equation was suggested for calculation of the compressive strength of HPC column with or without grout. FE analysis considering the contact surface between HPC and grout produced a good result matched to the test result.

• Journal of the Korea Society of Computer and Information
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• v.18 no.4
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• pp.35-43
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• 2013

As texture images have become prevalent throughout a variety of industrial applications, copyright protection of these images has become important issues. For this reason, this paper proposes a color-texture image watermarking algorithm utilizing texture properties inherent in the image. The proposed algorithm selects suitable blocks to embed a watermark using the energy and homogeneity properties of the grey level co-occurrence matrices as inputs for the fuzzy c-means clustering algorithm. To embed the watermark, we first perform a discrete wavelet transform (DWT) on the selected blocks and choose one of DWT subbands. Then, we embed the watermark into discrete cosine transformed blocks with a gain factor. In this study, we also explore the effects of the DWT subbands and gain factors with respect to the imperceptibility and robustness against various watermarking attacks. Experimental results show that the proposed algorithm achieves higher peak signal-to-noise ratio values (47.66 dB to 48.04 dB) and lower M-SVD values (8.84 to 15.6) when we embedded a watermark into the HH band with a gain factor of 42, which means the proposed algorithm is good enough in terms of imperceptibility. In addition, the proposed algorithm guarantees robustness against various image processing attacks, such as noise addition, filtering, cropping, and JPEG compression yielding higher normalized correlation values (0.7193 to 1).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.604-609
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• 2020

There are various methods of finishing concrete surfaces, and when considering workability, the spray method is effective, but rebound occurs. The allocation of rebound occurrence control should be adjusted according to the materials used. Thus, a basic study was conducted on multiple techniques for reducing the rebound incidence that are suitable for surface finishing materials containing a photocatalyst. A prior study derived the reduction effect and optimal mix ratio for photocatalytic performance. Based on that study, the rebound reduction was verified according to the specifications of the content and the mechanical durability characteristics of the mixed materials. Rebound, compressive strength, flexural rigidity, and table flow tests were done. The flow was fixed at 170±10 mm considering the workability of the mortar spray equipment. For the experimental variables, the rebound number was adjusted to the silica sand variables relative to the cement weight, and silica sands No. 5 and No. 7 were used. The results show the highest compression strength in the final S-1 variable, and the amount of rebound was minimized. These results were sufficiently filled with the bindings of the silica pores, which increased the binding force between the aggregates, resulting in a lower amount of rebound.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.7
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• pp.953-960
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• 2019

The Miller cycle is a diesel engine that has been developed in recent years that it can reduce NOx and improve fuel consumption by reducing the compression ratio through intake valve closing (IVC) time control. The Miller cycle can be divided into the early Miller method of closing the intake valve before the bottom dead center (BDC) and the late Miller method of closing the intake valve after the BDC. At low speeds, the late Miller method is advantageous as it can increase the volumetric efficiency; while at medium and high speeds, the early Miller method is advantageous because of the high internal temperature reduction effect due to the expansion of the intake air during the piston lowering from IVC to BDC. Therefore, in consideration of the ef ects of the early and late Miller methods, it is necessary to adopt the most suitable Miller method for the operating conditions. In this study, a two-stage turbo charge system was applied to four-stroke engines and the process of enhancing the Miller effect through a reduction of the intake and exhaust valve overlap as well as the valve change adjustment mechanism were considered. As a result, the ef ects of fuel consumption and Tmax reduction were confirmed by adopting the Miller cycle with a two-stage supercharge, a reduction of valve overlap, and an increase of suction valve lift.

• The Korean Journal of Emergency Medical Services
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• v.12 no.1
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• pp.17-26
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• 2008

Purpose : With a view to providing basic data to develop basic cardiopulmonary resuscitation education suitable for female college students, the basic cardiopulmonary resuscitation education was conducted to grasp students' knowledge, skill accuracy and the attitude change before and after the education. Methods : Convenience sampling was made on first graders(total-38 students) of K college located in K city, Chungcheongnam-do, and this was a preliminary research designed before and after choosing a single group. In terms of methods, the researchers as specified ; 1) Handed out questionnaires to students directly to make them fill in firsthand and collected the questionnaires. 2) Utilized Power Point materials based on 2005 AHA guideline and used Anne/Skill Reporter$^{(R)}$ torso produced by Leardal Inc, and Little Anne$^{(R)}$ to conduct practical education individually. 3) Asked students to give Anne/Skill Reporter$^{(R)}$ torso basic cardiopulmonary resuscitation five times with the ratio of 30:2, and then one of researchers filled in the evaluation sheet individually. 4) Evaluated the accuracy of students' ability to perform the resuscitation based on the record of Anne/Skill Reporter$^{(R)}$ integrated printer(which was the objective tool to grasp students' skills accuracy). 5) Gave out questionnaires to make students fill them in and then collected them, after completing the practical evaluation. Results : 1) In case of the attitude(confidence) about basic cardiopulmonary resuscitation, students' confidency rose from 14%(before the education) to 55.5%(after the education)- which was a positive change. 2) In case of the attitude(educational necessity) about basic cardiopulmonary resuscitation, students' confidency rose from 94.7%(before the education) to 100%(after the education)- which was a positive change. 3) As a result of the education, some female college students' scored knowledge about basic cardiopulmonary resuscitation. The average point also reached 88.95%(after the education), jump from 63.51%(before the education), which was the rise of 25.44%. 4) Regarding skill accuracy, pressure accuracy(%)($M{\pm}SD=91.37{\pm}14.16$) was higher than respiration accuracy(%)($M{\pm}SD=61.55{\pm}26.13$). Conclusion : The result showed that students' attitude(confidence, on basic cardiopulmonary resuscitation changed positively, and meaningful difference(p= .000) existed in the change of students' knowledge. Anne/Skill Reporter$^{(R)}$ performance showed that the accuracy of mouth-to-mouth resuscitation was lower than that of chest compression.