• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.423-430
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• 2014

Noise and vibration, which occur in a pipe, are usually caused by the interaction between the turbulent flow and nearby wall. Although it can be estimated by a simple case of expanded pipes having complex turbulent flow, the radiated noise is highly dependent upon the size, shape, and thickness of the given model. In addition, the radiated noise propagates and has serious interference and destabilization effects on the surrounding systems, which can lead to fatigue fracture and failure. This study took advantage of the variety of commercial programs, such as FLUENT (flow solver), NASTRAN (dynamic motion solver of complex structures) and VIRTUAL LAB (radiated noise solver) based on the boundary element method (BEM), to understand the underlying physics of flow noise. The expanded pipe has separation and a high pressure drop because of the abrupt change in the cross-section. Based on the radiated noise calculations, the noise level was reduced to around 20 dB in the range of 100-500 Hz.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.9-17
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• 2013

A considerable deal of work has been carried out to get an insight into the gas-solid suspension flows and to specify the particle motion and its influence on the gas flow field. In this paper an attempt is made to develop an analytical model to study the effect of nozzle inlet/exit pressure ratio, particle/gas loading and the particle diameter effect on gas-solid suspension flow. The effect of the particle/gas loading on the mass flow, Mach number, thrust coefficient and static pressure variation through the nozzle is analyzed. The results obtained show that the presence of particles seems to reduce the strength of the shock wave. It is also found that smaller the particle diameter is, bigger will be the velocity as bigger particle will have larger slip velocity. The suspension flow of smaller diameter particles has almost same trend as that of single phase flow with ideal gas as working fluid. Depending on the ambient pressure, the thrust coefficient is found to be higher for larger particle/gas loading or back pressure ratio.

• 모자간호학회지
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• v.2 no.1
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• pp.34-44
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• 1992

지난 10년 동안 구미에서는 부모-아동 관계 영역에 혁신을 가져왔다. 특히 부모-아동 애착이론의 획기적인 변화로 가족 중심 출산 경험을 강조하고 있다. 과거에는 남편이 아내의 출산에 참여하던 것이 타부시되어 왔지만 애착의 개념이 대두되면서 남편도 출산에 함께 참여하도록 고려하여 임신에서부터 부부가 함께 이 과업을 완수하도록 모든 환경을 변화시키고 있다. 애착이론은 다양하여 정신분석이론, 학습이론, 인지발달이론과 동물 행동학적 측면에서 이해되고 있다. 다양한 이론적 배경과 개념들을 가지고 아버지-아동의 애착 및 유대관계에 대한 연구가 지난 10여년 이상 되어오고 있다. 가장 관심의 촛점이 되어 연구 되어온 것으로는 애착형성을 위해 중요하다고 하는 민감한 시기(Critical period)를 중심으로 애착의 특성인 시각, 청각, 촉각, 상호호혜적 관계, 긍정적 애정을 바탕으로 연구되어졌다. 이 연구는 부아 애착(Paternal Infant Attachment)의 연구를 연구방법, 측정도구 및 방법상문제와 변수들을 중심으로 재정리하여, 이 분야에 있어서 앞으로의 연구 방향을 살펴보았다. 17편의 연구들을 각각 년도, 표본수, 방법 및 측정, 결과 및 비고난을 비교 분석하여 도표를 작성하였다. 이론적 기틀과 문헌고찰에 근거하여 다음과 같은 적용과 제언을 한다. 1. 출산전 아버지의 특성에 대한 사정이 필요하다. 2. 연구자가 집단간 비교를 용이하게 하기 위해 연구전에 표본의 특성을 정확히 기술해야 한다. 3. 부모와 아버지의 과거력에 대한 상세한 정보수집이 강조되어야 한다. 4. 앞으로의 연구는 이론적 모델에 근거하여 이루어져, 대중교육 뿐 아니라 정책 결정에 기여해야 한다. 5. 연구결과 평가와 해석을 위해 정확한 이론적 근거가 필요로 된다. 6. 간호연구는 부적절한 부아 애착 형성에 있어서 아버지의 특성을 확인하고 부아유대와 애착 증진의 요소를 파악해야한다. 7. 부아 유대에 대한 위협요소 확인을 위한 도구개발과 그들에 대한 효과적인 간호전략이 필요 된다. 8. 가족에 있어서 모든 부모행위가 하나의 독립변수로서 연구되어야 하고 부아유대 증진에 관한 연구가 시도되어야겠다. 오늘날 부모들은 임신기간동안 많은 정보에 접하기를 원한다. 산전, 산후의 교육과 지식은 긍정적인 부아 관계를 증진시키고, 이것은 아동의 발달에 크게 기여할 수 있다. 긍정적으로 이러한 관계는 가족단위를 강하게 통합시키게 되므로 건강관리자(Health care workers)들은 애착에 대해 높은 관심을 갖어야 하겠다.

• Korean Journal of Childcare and Education
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• v.11 no.3
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• pp.85-102
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• 2015

The purpose of this study is to investigate the variables that affect the problem behavior of children and to examine the relationships between problem behavior of young children in relation to the child's characteristics(temperament and ego-resiliency), the mother's characteristics(parenting stress and personality characteristics), and the teacher's characteristics(teacher-child relationship and emotional expressiveness). The researcher surveyed 314 parents and 56 teachers of young children in the transitional period from 32 early childhood institutes in Daejeon. The summaries of the results of the study are as seen below. First, the child's gender and mother's education were statistically significant variables in explaining the variance in problem behavior of young children. More boys than girls showed more problem behaviors and children of mothers who graduated university showed less problem behavior. Second, teacher-child relationship was the most predictive variable in problem behavior of young children. Children who had good relationships with their teachers showed less problem behavior and children who had poor relationships with their teachers showed more problem behavior. The results of this study can provide basic data for consulting and developing program to prevent and treat the problem behavior of young children to consider the development of children.

• Journal of the Korea Society of Computer and Information
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• v.25 no.11
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• pp.41-50
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• 2020

Sentimental analysis begins with the search for words that determine the sentimentality inherent in data. Managers can understand market sentimentality by analyzing a number of relevant sentiment words which consumers usually tend to use. In this study, we propose exploring performance of feature selection methods embedded with Particle Swarm Optimization Multi Objectives Evolutionary Algorithms. The performance of the feature selection methods was benchmarked with machine learning classifiers such as Decision Tree, Naive Bayesian Network, Support Vector Machine, Random Forest, Bagging, Random Subspace, and Rotation Forest. Our empirical results of opinion mining revealed that the number of features was significantly reduced and the performance was not hurt. In specific, the Support Vector Machine showed the highest accuracy. Random subspace produced the best AUC results.

• Geophysics and Geophysical Exploration
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• v.19 no.1
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• pp.20-28
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• 2016

Recently many sinkholes have appeared in urban areas of Korea, threatening public safety. To predict the occurrence of sinkholes, it is necessary to investigate the existence of cavity under urban roads. Ground-penetrating radar (GPR) has been recognized as an effective means for detecting underground cavity in urban areas. In order to improve the understanding of the governing physical processes associated with GPR wave propagation, and interpret underground cavity effectively, a theoretical approach using numerical modeling is required. We have developed an algorithm employing a three-dimensional (3D) staggered-grid finite-difference time-domain (FDTD) method. This approach allows us to model the full electromagnetic wavefield associated with GPR surveys. We examined the GPR response for a simple cavity model, and the modeling results showed that our 3D FDTD modeling algorithm is useful to assess the underground cavity under urban roads.

• Journal of Convergence for Information Technology
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• v.7 no.3
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• pp.153-158
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• 2017

The certification for Smart Factory supoort successful management of organization while providing strategic plans to the issue of manufacturing process. In Korea, these standards are prepared as the national standards since 2015, and also, there are actions being taken to adpot the certification for Smart Factory. However, to adopt such certification, it is required that the certification operation system needs to be organized, as well as that the society in general should understand about Smart Factory. Accordingly, it is even more required an review on the adoption of the system. This study has the purpose in surveying a variety of atakeholders' perception for the adoption of Smart Factory certification given the circumstance that the cetitification is implemented through literature review and in-depth interviews. This study will be provide significant implication to build a successful plan for the adoption of Smart Factory certification by reviewing perception of professional and problem, strategy of this certification.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.263-271
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• 2016

Software requirement analysis is necessary for successful software development project. Specially, incomplete requirement is the most influential causes of software project failure. Incomplete requirement can bring late delay and over budget because of the misunderstanding and ambiguous criteria for project validation. Software requirement patterns can help writing more complete requirement. These can be a reference model and standards when author writing or validating software requirement. Furthermore, when a novice writes the software scenario, the requirement patterns can be one of the guideline. In this paper proposes an automatic approach to identifying software scenario patterns from various software scenarios. In this paper, we gathered 83 scenarios from eight industrial systems, and show how to extract 54 scenario patterns and how to find omitted action of the scenario using extracted patterns for the feasibility of the approach.

• The Journal of Korean Association of Computer Education
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• v.16 no.3
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• pp.99-105
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• 2013

The FPGA-based emulation is an essential step in ASIC design for validation. For emulation with maximal frequency, it is crucial to understand the FPGA characteristics. This paper attempts to analyze the performance characteristics of the modern FPGAs from renowned vendors, Xilinx and Altera, with a case study utilizing various adders and MIPS CPU. Unlike the common wisdom, ripple-carry adder (RCA) does not utilize the inherent carry-chain inside FPGAs when structurally designed based on 1-bit adders. Thus, the RCA shows the inferior performance to the other types of adders in FPGAs. Our study also reveals that FPGAs from Xilinx exhibit different characteristics from the ones from Altera. That is, the prefix adder, which is optimized for speed in ASIC design, shows the poor performance on Xilinx devices, whereas it provides a comparable speed to the IP core on Altera devices. It suggests that error-prone manual change of the original design can be avoided on Altera devices if area is permitted. Experiments with MIPS CPU confirm the arguments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.15-24
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• 2000

The dielectric relaxation of high-dielectric capacitors could be understood as a dynamic property of the capacitor in the time domain, which is regarded as a primarily important charge loss mechanism during the refresh time of DRAMs. Therefore, the equivalent circuit of the dielectric relaxation of the high-dielectric capacitor is essentially required to investigate its effects on DRAM. Nevertheless, There is not any theoretical method which is generally applied to realize the equivalent circuit of the dielectric relaxation. Recently, we have developed a novel procedure for the circuit modeling of the dielectric relaxation of high-dielectric capacitor utilizing the frequency domain. This procedure is a general method based on theoretical approach. We have also verified the feasibility of this procedure through experimental process. Finally, we successfully investigated the effect of dielectric relaxation on DRAM operation with the obtained equivalent circuit through this new method.