• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3692-3697
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• 2015

A screw is a type of fastener characterized by a helical ridge known as thread. The demands for screws with the miniaturization and weight reduction are increasing for the trend of small size of mobile devices. The successful designs of mold and process are very important to obtain screws with good mechanical properties and high precision. In this study, the design of cold forging process of micro screw was carried out by using finite element method. In particular, in order to investigate the effects of die geometries and friction, design of experiment method was adopted and it was revealed that the friction was the dominant factor of folding defects. From these results, the design of die was modified and experiments were carried out with the modified die. From the experimental results, it was found that the folding defects disappeared.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.26-38
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• 2020

Mixture design of self-compacting concrete is a typical multi-criteria decision making problem and conventional mixture designs are based on the low level engineering method like trials and errors through iteration method to satisfy the various requirements. This study concerns with performing the straightforward multiobjective design optimization of economic SCC mixture considering relative importances of the various requirements and cost-effectives of SCC. Total five requirements of 28day compressive strength, filling ability, segregation stability, material cost and mass were taken into consideration to prepare the objective function to be formulated in form of the weighted-multiobjective mixture design optimization problem. Economic SCC mixture computational design can be given in a rational way which considering material costs and the relative importances of the requiremets and from the result of this study it is expected that the development of SCC mixtue computational design and the consequent univeral concrete material design optimization methodology can be advanced.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.392-403
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• 1997

There is a strong international move towards performance based fire regulations for buildings with New Zealand and Australia at the forefront of research in this fold. The reform of regulations is thought to offer more innovation and flexibility in building design and greater cost effectiveness in construction. An important part of the research in this area is related to the development of agreed approaches to fire safety design, such as the Fire Code Reform Centre's "Fire Engineering Guidelines" or New Zealand's "Fire Engineering Design Guide". Such design process documents have incorporated or referenced much of the latest research in areas such as: tenability criteria fire compartment models egress models risk assessment. Use of such design guidelines or equivalents in major projects in countries such as Hong Kong and Australia have highlighted where fro engineering can offer real benefits to building designers and ultimately building owners and operators. However, there is still much research to be done and use of a systematic, logical design approach clearly identifies where design data or modelling techniques are still urgently required. Such areas are: fire growth rates and peak heat release rates for non-residential occupancies pre-movement times related to egress experimental validation and limits of applicability of CFD and other compartment Ire models probability/reliability data on fire protection systems for risk based analysis. Examples from case studies will be shown where lack of such research and poor judgement can lead to inferior design solutions or where unnecessarily conservative designs can lead to cost excesses. In summary, the link between Ire engineering designers and the research community is very important to highlight areas of fire research that will have the most benefit to the building and construction industry.nstruction industry.

• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.569-582
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• 2007

Digital watermarking technique for copyright protection and prevention of illegal copy and distribution can provide the reliable transaction to both buyer and seller in e-commerce through the cryptographic protocol such as 'Buyer-seller watermarking protocol'. Recently there has been researched about some cryptographic protocols for watermarking system but there has no yet mentioned about the implementation of practical watermarking technique in protocol. This paper presents the watermark embedding technique based on POCS in buyer-seller watermarking protocol. The proposed method designs the robust convex set based on EZW and the invisible convex set using PSNR and then projects into two sets until the convergence condition is satisfied. Experimental results verified that BER of watermark that is embedded by the proposed method has lower 0.02-0.10 than BER of the conventional method.

• Journal of Convergence for Information Technology
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• v.9 no.11
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• pp.71-80
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• 2019

This study aims to understand the research trends in visiting nursing through an analysis of 282 research papers published in Korean journals between 1993 and 2018. The number of research papers has consistently increased since 1993 while it slightly decreased in 2014-2018. Of the three types of visiting nursing in Korea, more than 50% of the studies(154, 53.5%) were conducted for hospital based home care services. For the research topics, many studies addressed visiting nursing services(40, 13.8%) and program and technology development of visiting nursing(38, 13.1%). Also, there were many quantitative studies(269, 95.4%) compared to qualitative(9, 3.2%) or mixed methods(4, 1.4%) studies. The study findings suggested the needs for further studies that develop programs for patients and strengthen competencies of visiting nurses. Also, more experimental, qualitative, or mixed methods study designs need to be applied.

• Structural Engineering and Mechanics
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• v.50 no.5
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• pp.635-652
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• 2014

Creep and shrinkage behaviour of an ultra lightweight cement composite (ULCC) up to 450 days was evaluated in comparison with those of a normal weight aggregate concrete (NWAC) and a lightweight aggregate concrete (LWAC) with similar 28-day compressive strength. The ULCC is characterized by low density < 1500 $kg/m^3$ and high compressive strength about 60 MPa. Autogenous shrinkage increased rapidly in the ULCC at early-age and almost 95% occurred prior to the start of creep test at 28 days. Hence, majority of shrinkage of the ULCC during creep test was drying shrinkage. Total shrinkage of the ULCC during the 450-day creep test was the lowest compared to the NWAC and LWAC. However, corresponding total creep in the ULCC was the highest with high proportion attributed to basic creep (${\geq}$ ~90%) and limited drying creep. The high creep of the ULCC is likely due to its low elastic modulus. Specific creep of the ULCC was similar to that of the NWAC, but more than 80% higher than the LWAC. Creep coefficient of the ULCC was about 47% lower than that of the NWAC but about 18% higher than that of the LWAC. Among five creep models evaluated which tend to over-estimate the creep coefficient of the ULCC, EC2 model gives acceptable prediction within +25% deviations. The EC2 model may be used as a first approximate for the creep of ULCC in the designs of steel-concrete composites or sandwich structures in the absence of other relevant creep data.

• The Journal of Korean Society for School & Community Health Education
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• v.18 no.2
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• pp.27-42
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• 2017

Objectives: The purpose of this study was to investigate the characteristics of smoking prevention programs and their effectiveness for Korean school-aged children and adolescents by using systematic review and meta-analysis. Methods: Electronic searches were performed in RISS, NAL, DBPia, KISS using keywords according to inclusion criteria. 21 studies published from 2003 to the first half of 2017 that dealt with effects of smoking prevention programs for school-aged children and adolescents were selected for systematic review. Results: All 21 studies were quasi-experimental research designs. More than half of the programs(66.7%) were conducted for male and female. Most of the programs were conducted more than once a week(71.4%). 14 studies(66.7%) did not report using a theoretical model. Five dependent variables(knowledge of smoking, attitude toward smoking, non-smoking intention, self-assertiveness, and self-efficacy) were selected to measure the effectiveness of the smoking prevention programs. Knowledge of smoking was the most effective at hedge's g=0.673. Self-efficacy and self-assertiveness variables were statistically significant at hedge's g=0.461 and hedge's g=0.279, respectively. Effect sizes of attitude toward smoking and non-smoking intention were not statistically significant compared to the control group. As a result of the moderator effect analysis on the knowledge of smoking variable, the statistically significant variables were 'gender of participants'(p<0.01) and 'duration of the program'(p<0.001). Conclusions: The results of this study using systematic review and meta-analysis will be evidence-based data for researchers conducting smoking prevention programs in school-aged children and adolescents.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.2
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• pp.83-91
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• 2021

Seismic designs for Korean nuclear power plants (NPPs) under earthquakes' design basis are noticed due to the recent earthquake events in Korea and Japan. Japan has developed the technologies and experiences of the NPPs through theoretical research and experimental verification with extensively accumulated measurement data. This paper describes the main features of the design-time history complying with the Japanese seismic design standard. Proper seed motions in the earthquake catalog are used to generate one set of design time histories. A magnitude and epicentral distance specify the amplitude envelope function configuring the shape of the earthquake. Cumulative velocity response spectral values of the design time histories are compared and checked to the target response spectra. Spectral accelerations of the time histories and the multiple-damping target response spectra are also checked to exceed. The generated design time histories are input to the reactor building seismic analyses with fixed-base boundary conditions to calculate the seismic responses. Another set of design time histories is generated to comply with Korean seismic design procedures for NPPs and used for seismic input motions to the same reactor containment building seismic analyses. The responses at the dome apex of the building are compared and analyzed. The generated design time histories will be also applied to subsequent seismic analyses of other Korean standard NPP structures.

• Journal of Korean Medicine Rehabilitation
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• v.29 no.2
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• pp.171-188
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• 2019

Objectives The purpose of this thesis is to compare and analyze outcomes of case studies and controlled studies about Hwangryunhaedok-tang (HHT) pharmacopuncture in clinical studies. Based on these studies reporting clinical effects by using HHT pharmacopuncture, we object to deduct the comparative review in applying clinical disorders limitedly. And conclusionally, by using this comparative review, we aim to make the fine evidence in treating clinical specific diseases. Methods We searched 106 studies about HHT pharmacopuncture from 6 Korean web databases by using in Korean word 'Hwangryunhaedok-tang pharmacopuncture'. This search had been progressed throughout 1 month (January, 2019). There was 106 thesis and we excluded studies that are not related to HHT pharmacopuncture, experimental research, not the case report or randomized controlled trials, non-randomized controlled trials, not using HHT pharmacopuncture, not using only one pharmacopuncture, and not using HHT pharmacopuncture for major treating method. As a result, 39 thesis are selected as a population. Results We analyzed 34 case reports and 5 controlled studies. As the final outcome, HHT pharmacopuncture was used in musculoskeletal diseases, dermatopathy, and 32 specific diseases. Conclusions After analyzing 39 studies, effective symptom changes clinically and statistically by using HHT pharmacopuncture herbal acupuncture were identified. However, these thesis designs were reported deficiently in many parts such as not excluding other confounding variables. After modifying defects of thesis design and conduct study, it can play a role as the evidence using HHT pharmacopuncture more precisely.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.1
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• pp.1-7
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• 2019

In the modern industrial period, the introduction of mass production was most important progress in civilization. Die-casting process is one of main methods for mass production in the modern industry. The aluminum die-casting in the mold filling process is very complicated where flow momentum is the high velocity of the liquid metal. Actually, it is almost impossible in complex parts exactly to figure the mold filling performance out with the experimental knowledge. The aluminum die-castings are important processes in the automotive industry to produce the lightweight automobile bodies. Due to this condition, the simulation is going to be more critical role in the design procedure. Simulation can give the best solution of a casting system and also enhance the casting quality. The cost and time savings of the casting layout design are the most advantage of Computer Aided Engineering (CAE). Generally, the relations of casting conditions such as injection system, gate system, and cooling system should be considered when designing the casting layout. Due to the various relative matters of the above conditions, product defects such as defect extent and location are significantly difference. In this research by using the simulation software (AnyCasting), CAE simulation was conducted with three layout designs to find out the best alternative for the casting layout design of an automotive Oil Pan_BJ3E. In order to apply the simulation results into the production die-casting mold, they were analyzed and compared carefully. Internal porosities which are caused by air entrapments during the filling process were predicted and also the results of three models were compared with the modifications of the gate system and overflows. Internal porosities which are occurred during the solidification process are predicted with the solidification analysis. And also the results of the modified gate system are compared.