• Advances in aircraft and spacecraft science
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• 제6권3호
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• pp.225-238
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• 2019

A spike attached to a blunt nosed body significantly alters its flow field and influences the aerodynamic coefficients at hypersonic speed. The basic body is an axisymmetric, with a hemisphere nose followed by a cylindrical portion. Five different types of spikes, namely, conical aerospike, hemisphere aerospike, flat-face aerospike, hemisphere aerodisk and flat-face aerodisk are attached to the basic body in order to assess the aerodynamic characteristic. The spiked blunt body without the aerospike or aerodisk has been set to be a basic model. The coefficients of drag, lift and pitching moment were measured with and without blunt spike body for the length-to-diameter ratio (L/D) of 0.5, 1.0, 1.5 and 2.0, at Mach 6 and angle of attack up to 8 degrees using a strain gauge balance. The measured forces and moment data are employed to determine the relative performance of the aerodynamic with respect to the basic model. A maximum of 77 percent drag reduction was achieved with hemisphere aerospike of L/D = 2.0. The comparison of aerodynamic coefficients between the basic model and the spiked blunt body reveals that the aerodynamic drag and pitching moment coefficients decrease with increasing the L/D ratio and angle of attack but the lift coefficient has increasing characteristics.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.125-130
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• 1992

If reinforced concrete beam exists crack, ultimate shear transfer strength and shear hardness of section with crack substantially decrease. In this study , five model beams were designed for the objective of clarfying contributions of three shear resistant elements : the compression zone of concrete, dowel action of tension reinforcement, aggregate interlock across cracks, The shear force carried by each resistant element was calculated from the detailed strain data on the contributions to the shear capacity of beams of the shear forces carried by the other three resistant element. The test result follows : 1) Compression zone of concrete (C)-56.2%, 2) Dowel action of tension reinforcement (D)-18.0%, 3)Aggregate Interlock(A)-25.8%.

• 융합경영연구
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• 제8권1호
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• pp.12-19
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• 2020

Purpose - Strategic causes for the failure include unrealistic growth, overexpansion, unfamiliar new markets, volume obsession, unrealistic promises and poor project selection. Organizational causes are insufficient capital and profits, lack of business knowledge, poor financial management, poor sales skills, inadequate marketing, poor leadership, poor leadership transfer, project losses, poor field performance and owner bankruptcy. Uncontrollable causes include industry and economic weakness and banking and surety changes. While helpful, the list provides insufficient clarity regarding the causal roots of failure. Research design, data and methodology - The research framework to organize the information involved with many of the recent and large failures in the industry. Results - This research then identified five dominant root causes - excessive egoism, poor strategic leadership, too much change, loss of discipline and inadequate capitalization. Conclusion - Finally, additional input from external forces may accelerate the firm's pace to failure. It is important on the development of diagnostic tools that are based on this model and that will provide new ways to assess a conglomerate's level of risk for incurring a financial crisis.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2022년도 제66차 하계학술대회논문집 30권2호
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• pp.687-688
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• 2022

국내 커피산업에 있어서 2020년 기준으로 개인 커피전문점 점포수는 7만 5520곳으로 전체 커피전문점 점포수의 90%를 차지하였으나, 국내 3대 대형 커피프랜차이즈(스타벅스, 투썸플레이스, 이디야)의 매출액 비중은 60%으로 대형 커피프랜차이즈의 매출비중이 매우 높다[1]. 개인 커피전문점의 경우 대형프랜차이즈에 비해 자본력과 브랜드 파워 부족으로 어려움을 겪고 있는데, 본 연구에서는 마이클포터의 Five-Forces Model을 커피산업에 적용하여 한국 커피산업 외부환경을 분석하고, VRIO 분석을 통해 개인 커피전문점 내부자원을 분석하여 개인 커피전문점의 발전을 위한 경영전략을 도출하고자 한다.

• Computers and Concrete
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• 제15권6호
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• pp.921-933
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• 2015

The aim of this study is to determine the earthquake performances of reinforced concrete (R/C) residential buildings in Turkey and to analyze the parameters that affect the performance. The performance of Turkish residential buildings, determined by their levels of damage, directly relates to their structural systems. Damage parameters observed from previous earthquakes define structural parameters selected to be used in the present study. Five different types of frame R/C buildings were modeled. For the analysis, the model buildings vary according to the number of stories, column sizes, and reinforcement and concrete strength parameters. The analyses consider gravity forces and earthquake loads through 1975 and 2007 Turkish design codes. In a total of 720 different R/C buildings were investigated for the analysis to obtain capacity curves. A performance evaluation was employed by considering the Turkish design code (TDC-2007). The current study ignores irregularities such as soft stories or short columns. The study's analysis considers a comparison of the parameters' influence on the structural performance of the model buildings.

• Journal of Information Technology Applications and Management
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• 제13권4호
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• pp.41-56
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• 2006

The real estate portal has grown into a successful e-Business model that is combined on and off line. Although IT technologies have shown rapid growth, the real estate portals have failed to satisfy the expectations of the Internet users. Based on Michael Porter's competitive forces framework, this study proposes five competitive strategies for continuing growth of the real estate portals. First, to strengthen bargaining power against supplier, buyer and potential new entrants, the real estate portals need to construct a basic network that is cost efficient and maintains real estate goods and makes profits by collaborative deals. Second, strengthen brand value and endeavor to escape from dependency on the Internet portals. Third, develop services to consider changed circumstances and give a lot of sources to make profit to real estate agencies. Fourth, concentrate on marketing to draw in the Internet users and adapt strategies that have been successful in other fields. Finally, real estate fields can seek out ideas for developing new business models from other successful e-Business models and should benchmark them to reduce expenses to a minimum and increase benefits to a maximum.

• Steel and Composite Structures
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• 제32권4호
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• pp.497-507
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• 2019

Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.325-337
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• 2019

In the present article, cross ply laminated composite plates are considered and a simple sinusoidal shear deformation model is tested for analyzing their flexural, stability and dynamic behaviors. The model contains only four unknown variables that are five in the first order shear deformation theory (FSDT) or other higher order models. The in-plane kinematic utilizes undetermined integral terms to quantitatively express the shear deformation influence. In the proposed theory, the conditions of zero shear stress are respected at bottom and top faces of plates without considering the shear correction coefficient. Equations of motion according to the proposed formulation are deduced by employing the virtual work principle in its dynamic version. The analytical solution is determined via double trigonometric series proposed by Navier. The stresses, displacements, natural frequencies and critical buckling forces computed using present method are compared with other published data where a good agreement between results is demonstrated.

• Wind and Structures
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• 제33권6호
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• pp.437-446
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• 2021

As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

• Earthquakes and Structures
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• 제24권1호
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• pp.21-36
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• 2023

Structural vibrations generated by earthquakes and wind loads can be controlled by varying the structural parameters such as mass, stiffness, damping ratio, and geometry and providing a certain amount of passive or active reaction forces. A Double-Tuned Mass Dampers (DTMDs) system, which is simple and more effective than the conventional single tuned mass damper (TMD) system for vibration mitigation is presented. Two TMDs tuned to the first two natural frequencies were used to control vibrations. Experimental investigations were carried out on a three degrees-of-freedom frame model to investigate the effectiveness of DTMDs systems in controlling displacements, accelerations, and base shear. Numerical models were developed and validated against the experimental results. The validation showed a good match between the experimental and numerical results. The validated model was employed to investigate the behavior of a five degrees-of-freedom shear building structure, wherein mass dampers with different mass ratios were considered. The effectiveness of the DTMDs system was investigated for harmonic, seismic, and white noise base excitations. The proposed system was capable of significantly reducing the story displacements, accelerations, and base shears at the first and second natural frequencies, as compared to conventional single TMD.