• Geomechanics and Engineering
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• v.12 no.2
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• pp.313-326
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• 2017

Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.239-245
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• 2000

In this paper, the fundamental properties of diffractive optical element were investigated. Also, this work deals with theoretical approaches for achromatization in DOE's optical system based on thin lens theory. It is found that achromatization could be satisfied by one hybrid lens only, which is composed of a diffractive and a refractive element. In order to have compact optical system, we used the tele-photo type lens composed of a positive and a negative power elements instead of retro-focus lens. From the Gaussian brackets and Seidel aberration theory, the initial design was numerically obtained. The aberration properties of an initial design was aplanat and flat field. In order to correct the chromatic aberrations, refractive and diffractive elements were used on front element. This hybrid lens is also useful for correction of higher order aberrations. Compared to conventional design composed of refractive lenses only, this approach dramatically improved the compactness of the optical system. Finally, residual aberration balancing results in a lens with focal length of 3.89 mm and overall length of 5.19 mm, which has enough performance over an f-number of 4.0. Also, it is expected to fulfill all the requirements of a digital still camera lens. This optical system is superior to the current refractive lens system in the number of elements, weight, and aberration properties. rties.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.3
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• pp.1-1
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• 1987

The accurate prediction of the ship wave resistance is very important to design ships which operate satisfactorily in a wave environment. Thus, work should continue on development and validation of methods to compute ship wave patterns and wave resistance. Research efforts to improve the prediction of ship waves and wavemaking resistance are categorized in two major areas. First is the development of higher-order theories to take account of the nonlinear effect of the free surface condition and improved analytical treatment of the body boundary condition. Second is the development of direct numerical methods aimed at solving body and free-surface boundary conditions as accurately as possible. A new formulation of the slender body theory for a ship with constant speed is developed by Maruo. It is quite different from the existing slender ship theory by Vossers, Maruo and Tuck. It may be regarded as a substitute for the Neumann-Kelvin approximation. In present work, the method of asymptotic expansion of the Kelvin source is applied to obtain a new wave resistance formulation in fluid of finite depth. It takes a simple form than existing theory.

• Advances in concrete construction
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• v.9 no.3
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• pp.327-335
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• 2020

Concrete pipes are considered important structures playing integral role in spread of cities besides transportation of gas as well as oil for far distances. Further, concrete structures under seismic load, show behaviors which require to be investigated and improved. Therefore, present research concerns dynamic stress and strain alongside deflection assessment of a concrete pipe carrying water-based nanofluid subjected to seismic loads. This pipe placed in soil is modeled through spring as well as damper. Navier-Stokes equation is utilized in order to gain force created via fluid and, moreover, mixture rule is applied to regard the influences related to nanoparticles. So as to model the structure mathematically, higher order refined shear deformation theory is exercised and with respect to energy method, the motion equations are obtained eventually. The obtained motion equations will be solved with Galerkin and Newmark procedures and consequently, the concrete pipe's dynamic stress, strain as well as deflection can be evaluated. Further, various parameters containing volume percent of nanoparticles, internal fluid, soil foundation, damping and length to diameter proportion of the pipe and their influences upon dynamic stress and strain besides displacement will be analyzed. According to conclusions, increase in volume percent of nanoparticles leads to decrease in dynamic stress, strain as well as displacement of structure.

• Archives of Plastic Surgery
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• v.40 no.4
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• pp.312-319
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• 2013

Over the past decade, driven by advances in educational theory and pressures for efficiency in the clinical environment, there has been a shift in surgical education and training towards enhanced simulation training. Microsurgery is a technical skill with a steep competency learning curve on which the clinical outcome greatly depends. This paper investigates the evidence for educational and training interventions of traditional microsurgical skills courses in order to establish the best evidence practice in education and training and curriculum design. A systematic review of MEDLINE, EMBASE, and PubMed databases was performed to identify randomized control trials looking at educational and training interventions that objectively improved microsurgical skill acquisition, and these were critically appraised using the BestBETs group methodology. The databases search yielded 1,148, 1,460, and 2,277 citations respectively. These were then further limited to randomized controlled trials from which abstract reviews reduced the number to 5 relevant randomised controlled clinical trials. The best evidence supported a laboratory based low fidelity model microsurgical skills curriculum. There was strong evidence that technical skills acquired on low fidelity models transfers to improved performance on higher fidelity human cadaver models and that self directed practice leads to improved technical performance. Although there is significant paucity in the literature to support current microsurgical education and training practices, simulated training on low fidelity models in microsurgery is an effective intervention that leads to acquisition of transferable skills and improved technical performance. Further research to identify educational interventions associated with accelerated skill acquisition is required.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.551-556
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• 2008

Six Sigma keeps its continuous change in terms of its strategies and methodologies for 20 years since it is introduced in the industry Developing innovative business management strategies creating a higher synergy effect has been Pursued by combining Six Sigma and different business strategies. In fact, various research studies have been performed for grafting lean production theory with Six Sigma concept. Specifically, the companies which obtained positive results from the applications of Six Sigma are trying to adopt Lean Six Sigma theory for their business strategies. However, the research studies or the applications of Lean Six Sigma are insufficient in the construction industry compared to the other industries such as manufacturing. In order to deal effectively with this issue, this research study suggests the improved and restructured Six Sigma DMAIC processes by embodying the existing Six Sigma DMAIC processes applied on construction projects and improving them through the improvement territories of Lean Six Sigma studied in advance.

• Journal of dental hygiene science
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• v.18 no.1
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• pp.50-59
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• 2018

The purpose of this study was to develop a motivational interviewing (MI) training program to improve competency in communication and to effect the evaluated changes that would occur in dental students' counseling techniques as result of the training in the program. The study proceeded through the program via role-play practice, which was explained effectively during the MI program training process. A convenience sample of 43 fourth-year dental hygiene students was recruited. Twenty-two students were randomly assigned to the intervention group and 21 to the control group in the order of recruitment. The theoretical lecture was delivered over 3 hours and the practice was done in parallel by applying cases occurring in clinic settings. The practice was technical training, partner practice, and small group practice. The intervention group received three hour MI lecture while the control group received no lecture. Evaluation through role-play practice was separated according to "researcher's viewpoint," "counselor's role viewpoint," and "patient's role viewpoint." The results of the analysis showed that the intervention group had higher MI skills and ability than the control group. Furthermore, program participants showed positive impressions to the MI training program. The use of coaching sessions improved the MI techniques and counseling skills of dental hygiene students learning MI. The effect of the application of the MI training program was that the MI training improved counseling skills and interviewing abilities. Moreover, continuous training and feedback enhanced MI techniques and core skills. Training using lectures in parallel with practice rather than education through theory alone improved students' techniques. Application of role play through the combined method of the MI program was confirmed by an effective training method.

• Journal of the Korea Furniture Society
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• v.26 no.3
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• pp.267-273
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• 2015

This study is a review on the relationship between furniture purchasers and producers in the Joseon period. Understanding the relationships in our traditional spirit and the Joseon furniture that reflects a aesthetic sense is a meaningful work. Joseon was to build an ideal country which put emphasis on the order and harmony through Theory of 'Yeak' as the confucianism nation. Human aesthetics, which emphasis on the spiritual value by confirmity to nature and forcus on the relaxed, deficient personality rather than completeness was established as the central formative consciousness of the Joseon Dynasty. The nature of things in the confucian scholar prior to the representations of things is expressed in the form of master craftsman's skill and soul. Formative consciousness of the confucian scholar is to realize ideals by communciation and interchange with master craftsman's soul in the form of the Joseon furniture. The beauty of restraint and brevity in the Joseon Dynasty furniture includes meanings and procedures of art work. It implies an orderer's purpose of production and a producer's products. Understanding the spirit of times in the production becomes the cornerstone capable of getting closer to the furniture ultimate proper function. These problems have a very close relationship with the problems of modern people's commnuication. We expect an even higher growth of the furniture by achieving more improved communication based on the consumer's great insight and the producer's passion.

• Steel and Composite Structures
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• v.44 no.4
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• pp.531-543
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• 2022

An exact dynamic analytical method for free vibrations of continuous partial-interaction composite beams is proposed based on the Timoshenko beam theory. The main advantage of this method is that the independent shear deformations and rotary inertia of sub-beams are considered, which is more in line with the reality. Therefore, the accuracy of eigenfrequencies obtained by this method is significantly improved, especially for higher order modes, compared to the existing methods where the rotary angles of both sub-beams are assumed to be equal irrespective of the differences in the shear stiffness of each sub-beam. Furthermore, the solutions obtained by the proposed method are exact owing to no introduction of approximated displacement and force fields in the derivation. In addition, an exact analytical solution for the case of simply supported is obtained. Based on this, an approximate expression for the fundamental frequency of continuous partial-interaction composite beams is also proposed, which is useful for practical engineering applications. Finally, the practicability and effectiveness of the proposed method and the approximate expression are explored using numerical and experimental examples; The influence factors including the interfacial interaction, shear modulus ratio, span-to-depth ratio, and side-to-main span length ratio on the eigenfrequencies are presented and discussed in detail.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.373-384
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• 1999

The shell structures with composite materials have the advantages in strength, corrosion resistance, and weight reduction. The objective of this study is to analyze anisotropic composite circular cylindrical shells with shear deformation theory. In applying numerical methods to solve differential equations of anisotropic shells, this paper use finite difference method. The accuracy of the numerical method can be improved by taking higher order of interval ${\Delta}$ to reduce error. This study compares the results of finite difference method with the results of ANSYS based on finite element method. Several numerical examples show the advantages of the stiffness increasement when the composite materials aroused. Therefore, it is expected that results of this study give various guides for change of the subtended angles, load cases, boundary conditions, and side-to-thickness ratio.