• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.6
• /
• pp.713-725
• /
• 2004

The two-dimensional motion of a freely falling circular cylinder in an infinite fluid is investigated numerically using combined formulation. The effect of vortex shedding on the motion of a freely falling cylinder is clearly seen: as the streamwise velocity of the cylinder increases due to gravity, the periodic vortex shedding induces a periodic motion of the cylinder. This motion in turn affects the flow field, which is manifested by the generation of the angular velocity vector of the cylinder parallel to the cross product of the gravitational acceleration vector and the transverse velocity vector of the cylinder. A correlation of St-Re relationship for a freely falling circular cylinder is drawn from the present results. The Strouhal number for a freely falling circular cylinder is found to be smaller than that for a fixed circular cylinder when the two Reynolds numbers based on the streamwise terminal velocity of a freely failing circular cylinder and the free stream velocity of a fixed one are the same. From "thought experiments", it is shown that the transverse motion of the cylinder plays a crucial role in reducing the Strouhal number and has an effect of reducing the Reynolds number from the viewpoint of the pressure coefficient. The mechanism of this reduction in the Strouhal number is revealed by the fact that the freely falling cylinder experiences a smaller lift force than the fixed one due to the transverse motion resulting in the retardation of the vortex shedding.

• 한국경영정보학회:학술대회논문집
• /
• 2008.06a
• /
• pp.400-410
• /
• 2008

As the number of blog users has been increasing significantly, a lot of studies have been carried out to find out what makes people use a blog or feel satisfied with it. However, most of the previous studies assumed that dissatisfaction is the opposite of satisfaction and a person who is dissatisfied with a blog does not use it, failing to explain about blog users who do not feel satisfied with their blogs but use them continually. In addition, the studies found out just blog users' motives and satisfying factors in using blogs, and did not suggest any way to improve and promote blog services. Against this backdrop, this study conducted a survey of blog users in order to examine how the satisfying factors of a blog selected through a prior study affect both satisfaction and dissatisfaction of a user. The survey results showed that the satisfying factors are divided into two groups: group A which affect satisfaction and dissatisfaction equally, and group B which affect them differently. Based on the results, this study subdivides group A into high involvement factors and low involvement ones, and group B into motivators, which strongly affect satisfaction, and hygiene factors, which strongly affect dissatisfaction. According to characteristics of each group, this study suggests ways to improve and promote blog services.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.32 no.3
• /
• pp.79-86
• /
• 1990

Based on limited number of tests on reinforced wood beams using polymer mortar in this study, following conclusions were drawn ; 1.Reinforcing compression side of wood beam using polymer mortar was effective in reducing deflection. 2.By increasing thickness of polymer mortar, effective beam stiffness was improved, but energy absorption was reduced. 3.Polymer mortar reinforcement improved compressive strength and reduced strain in compression side of the beam. Therefore, it was possible to change the failure mode from by compression in control beam to by tension in composite beams. 4.The composite beams that have more than 2cm of polymer mortar layer did not perform well because a strain redistribution and separation of meterials at interface were induced in moment span. 5.To maximize the load carrying capacity of composite beam, it is necessary to make polymer mortar and wood behave together without failing at interface. To do this, it is needed to use a polymer mortar which has high strength with such elastic modulus that is closer to elastic modulus of wood. otherwise, it is recommended to use shear connectors at interface to prevent separation of materials under ultimate load.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.15 no.7
• /
• pp.858-863
• /
• 2005

Sensor network is subject to novel problems and constraints because it is composed of thousands of tiny devices with very limited resources. The large number of motes in a sensor network means that there will be some failing nodes owing to the lack of battery in sensor nodes. Therefore, it is imperative to save the energy as much as possible. In this work, we propose energy efficient routing algorithm which is based on directed diffusion scheme. In the proposed scheme, some overloads required for reinforcing the gradient path can be effectively eliminated. Furthermore, in order to verify the usefulness of the proposed algorithm, several simulations are executed.

• Structural Engineering and Mechanics
• /
• v.63 no.5
• /
• pp.659-667
• /
• 2017

Rail support failure is inevitably subjected to track geometric deformations. Due to the randomness and evolvements of track irregularities, it is naturally a hard work to grasp the trajectories of dynamic responses of railway systems. This work studies the influence of rail fastener failure on dynamic behaviours of wheel/rail interactions and the railway tracks by jointly considering the effects of track random irregularities. The failure of rail fastener is simulated by setting the stiffness and damping of rail fasteners to be zeroes in the compiled vehicle-track coupled model. While track random irregularities will be transformed from the PSD functions using a developed probabilistic method. The novelty of this work lays on providing a method to completely reveal the possible responses of railway systems under jointly excitation of track random irregularities and rail support failure. The numerical results show that rail fastener failure has a great influence on both the wheel/rail interactions and the track vibrations if the number of rail fastener failure is over three. Besides, the full views of time-dependent amplitudes and probabilities of dynamic indices can be clearly presented against different failing status.

• Journal of the Korean Institute of Educational Facilities
• /
• v.27 no.2
• /
• pp.79-86
• /
• 2020

Since the introduction of the new Variation Type school, few studies have focused on students' adaptation to the changes in their learning environments at school. This paper is based on the Stage-Environment Fit theory, which asserts that a successful school life(in terms of motivation to learn) is ensured only when the school environment meets the social and emotional needs of students. Focusing on the third-grade student's adaptation to a new Variation Type school during their middle school period, the following conclusions were drawn. First, the transition to a new Variation Type school during middle school is much more difficult than adjusting to a new Variatio Type school upon admission to middle school. Second, this difficulty in adaptation is caused by socio-emotional dissatisfaction in adolescent students, for whom deconstruction of previous friendships can hinder motivation to learn. Third, third-grade students who experienced stress due to spatial changes tended to have a negative attitude towards the new Variation Type itself as they feel more tired from failing to use the space properly. Fourth, to transition successfully to a new Variation Type school, socio-emotional problems must be solved through the reduction of scale of the homebase, and the provision of various choices increasing the number of homebase.

• The Journal of the Korean dental association
• /
• v.16 no.2 s.105
• /
• pp.123-128
• /
• 1978

Sometimes in clinic, we have found that cast crown construction is necessary to fit the existing partial denture clasp, when the abutment is involved with caries, a failing restoration, periodontal disease, or fracture. This is important not only to protect the abutment tooth from missing, but to restore retention, bracing and support for partial denture. For constructing the cast crown, several methods have been reported by many of previous authors. The number of techniques reported during the past are ideal but have uncertain results However, with more improved and practical technic developed by me, the problem becomes more successful. One method in which does not need the laboratory technecian is the wax pattern has been made in chairside waxing by doctor himself. The other in which requires the laboratory technician is to use special impression method and articulator for laboratory waxing. In one case of the reported here, we have successful results in restoring the abutment with cast crown for original denture clasp.

• The Journal of Industrial Distribution & Business
• /
• v.10 no.4
• /
• pp.25-31
• /
• 2019

Purpose - A framework is suggested in this paper which will help crowdfunding platforms to match projects according to expectations of funders, leading to successful campaigns and thus increase the profitability of the crowdfunding platform. Research design, data, and methodology - The paper is theoretical and conceptual in nature which proposes a model for crowdfunding platforms to match expectations of crowds with project fundraisers. Results - Crowdfunding platforms are going through incremental innovations in order to match customer (funders and fundraisers) expectations. Leading crowdfunding platforms like Kickstart holds benchmark for other players in the market but the secret of success lies in matching quality projects with the appropriate funders. Crowdfunding platforms have to securitize the projects and allow only quality projects but also provide a wide range of options for funders. Thus, to manage this trade-off between quality and quantity of options, a framework is proposed. Conclusions - Crowdfunding platforms have to adopt a model which will help them in providing a perfect match between crowds and fundraisers. Each member of the crowd and every project will be assigned a category and rating based on the past records. Securitization of projects will help to entertain only demanded projects which will reduce the number of failing campaigns.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.11
• /
• pp.82-88
• /
• 2007

In this paper, we present a pattern comparison algorithm for reducing fault candidate lists. The number of fault candidates determines the total fault simulation time. To decrease the total fault diagnosis time, the reduction of the number of fault candidates is essential. Critical path tracing determines fault candidate lists detected by a set of tests using a backtracing algorithm starting at the primary outputs of a circuit. The proposed algorithm reduces fault candidates comparing failing patterns with good patterns during critical path tracing process. As we reduce all fault candidates of the circuit to more accurately suspected fault candidates, we can greatly reduce fault simulation time. The proposed algorithm greatly increases simulation speed than that of a conventional backtracing method. The proposed algorithm is applicable to both combinational and sequential circuits. Experimental results on ISCAS#85 and ISCAS#89 benchmark circuits showed fault candidates are pruned and fault diagnosis time is also decreased in proportion to fault candidate decrease.

• Journal of Agricultural Extension & Community Development
• /
• v.21 no.2
• /
• pp.211-254
• /
• 2014

Malawi's agricultural extension system has been subjected to a number of criticisms in recent times for failing to contribute significantly to agricultural development and for not responding to the needs of the smallholder farmers. Despite this, extension is still seen as key to improving poverty and rural livelihoods.There is a number of challenges facing extension that require a response from the public sector and other stakeholders. A clear and positive response to these challenges will help shape the future of agricultural extension in Malawi for the benefit of all farmers and the attainment of the broad policy objectives of government: democratization, market liberalization, decentralization, HIV/AIDS crisis, shrinking public sector resources, public sector reform, and co-ordination, etc. The mission is to provide pluralistic demand driven extensions services and promote equalisation and co-ordination in service provision in order to achieve food security at household level, there-by reducing poverty. On the other hand the vision is that 'All farmers' demand and access high quality extension services from those best able to provide them'. DAES implements its extension policy through the District Agricultural Extension Services System (DAESS), based on Model Village Approach.