• Smart Structures and Systems
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• v.21 no.3
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• pp.335-347
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• 2018

The fast-growing number of mobile and wearable applications has driven several innovations in small-scale electret-based energy harvesting due to the compatibility with standard microfabrication processes and the ability to generate electrical energy from ambient vibrations. However, the current modeling methods used to design these small scale transducers or microgenerators are applicable only for constant-speed rotations and small sinusoidal translations, while in practice, large amplitude sinusoidal vibrations can happen. Therefore, in this paper, we formulate an analytical model for electret-based microgenerators under general sinusoidal excitations. The proposed model is validated using finite element modeling combined with numerical simulation approaches presented in the literature. The new model demonstrates a good agreement in estimating both the output voltage and power of the microgenerator. This new model provides useful insights into the microgenerator operating mechanism and design trade-offs, and therefore, can be utilized in the design and performance optimization of these small structures.

• Wind and Structures
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• v.12 no.2
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• pp.151-177
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• 2009

The International Hurricane Research Center (IHRC) at Florida International University (FIU) is pursuing research to better understand hurricane-induced effects on residential buildings and other structures through full-scale aerodynamic and destructive testing. The full-scale 6-fan Wall of Wind (WoW) testing apparatus, measuring 4.9 m tall by 7.3 m wide, is capable of generating hurricane-force winds. To achieve windstorm simulation capabilities it is necessary to reproduce mean and turbulence characteristics of hurricane wind flows. Without devices and methods developed to achieve target wind flows, the full-scale WoW simulations were found to be unsatisfactory. To develop such devices and methods efficiently, a small-scale (1:8) model of the WoW was built, for which simulation devices were easier and faster to install and change, and running costs were greatly reduced. The application of such devices, and the use of quasiperiodic fluctuating waveforms to run the WoW fan engines, were found to greatly influence and improve the turbulence characteristics of the 1:8 scale WoW flow. Reasonable reproductions of wind flows with specified characteristics were then achieved by applying to the full-scale WoW the devices and methods found to be effective for the 1:8 scale WoW model.

• Journal of Korean Society of Disaster and Security
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• v.9 no.2
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• pp.43-52
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• 2016

Notwithstanding industrial accident decrease generally, Construction industry is on the rise recently. Most accident occurs in the small scale like as multiflex housing, remodeling, neighbourhood facility more than safety supervisor appointed large scale construction site. By the size of business place, 81.6% of total accident occurs mostly in small scale site that is bellow 120 billion won and 50 manpower. This paper aimed that small scale housing company achieve a zero hazard practising and understanding the safety adminstration standar d model easily and it applied firstly after investigating the operation condition of construction site safety control in small scale company propelling the complex style multiflex housing business.

• Journal of the Korean Solar Energy Society
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• v.29 no.6
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• pp.56-61
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• 2009

The effects of design parameters for small scale hydro power(SSHP) plants due to climate change have been studied. The model to predict hydrologic performance for SSHP plants is used in this study. The results from analysis far rainfall conditions based on KIER model show that the capacity and load factor of SSHP site had large difference between the period. Especially, the hydrologic performance of SSHP site due to rainfall condition of recent period varied in design flowrate sensitively. However climate change gave small effect in load factor of existing SSHP plant. And also, the methodology represented in this study can be used to decide the primary design specifications of SSHP sites.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.311-318
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• 2011

Small-scale reactors have recently attracted attention as a potential power generation source for the future. The Regional Energy Research Institute for Next Generation is currently developing a small-scale reactor called Regional Energy rX 10 MVA (REX-10). The current paper deals with a power system to be used with small-scale reactors for multi-purpose regional energy systems. This small nuclear system can supply electric and thermal energy like a co-generation system. The electrical model of the REX-10 has been developed as a part of the SCADA system. REX-10's dynamic and electromagnetic performance on the power system is analyzed. Simulations are carried out on a test system based on Ulleung Island's power system to validate REX-10 availability on a power system. RSCAD/RTDS and PSS/E software tools are used for the simulation.

• The Mathematical Education
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• v.40 no.2
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• pp.179-194
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• 2001

The seventh curriculum put into operation gradually from first-year student in 2000 academic years of elementary school is subject to form and apply a step-wise level curriculum. Mathematics(correspond to junior high school course from 7th school year to 9th school year) should apply a step-wise level curriculum from 7th school year in 2001 academic years. Accordingly, mathematics teachers must diagnose actual conditions of educations, distribution tables of test results, step-wise teaching-studying programs etc. They also make proper plans suitable for actual situations of each school, prepare appropriate teaching materials and aids. I investigated preceding studies planned for preparation of putting into operation of a step-wise level curriculum. It showed that most of the studies were conducted at schools of medium or large scale and studies conducted at schools of small scale was rare. There were 113 small scale middle schools out of total 297 middle schools in Kyongsangbuk-do area in 2000. In this situation, I felt necessities of modeling of a step-wise level curriculum suitable for small scale schools. In this study, I modeled a step-wise level curriculum suitable for small scale middle schools, applied this model to 44 students in M middle school. I modeled two types of curriculum. One is a step-wise level curriculum that execute special supplementation process to students who do not complete 7-가 step successfully. The other is a step-wise level curriculum which is a regular model for a step-wise level of 7-나 step. I carried out an academic achievement test and intimacy test about mathematics before and after the application of the model. In this study, I found out that this model was very effective in academic achievement of students and helpful to declined students in scholarship. In the intimacy test, It was found out that most of the students gained confidence in mathematics, felt less anxiety, formed positive self consciousness. Therefore, I think that this model will be helpful to the application of the seventh step-wise level curriculum.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.129-132
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• 2002

The purpose of this study was to disclose the problems of structural safety of small scale vinyl house through investigation of actural state of plastic greenhouses by region and growing crops and the objective of a field survey is to develop safety structural model of small scale vinyl house which accounts for the most part of local horticultural facility in order to reduce damage caused by strong wind and heavy snow repeatedly every year.

• Wind and Structures
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• v.15 no.1
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• pp.43-64
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• 2012

Many potential small wind turbine locations are near obstacles such as buildings and shelterbelts, which can have a significant, detrimental effect on the local wind climate. A neural network-based model has been developed which predicts mean wind speed and turbulence intensity at points in an obstacle's region of influence, relative to unsheltered conditions. The neural network was trained using measurements collected in the wakes of 18 scale building models exposed to a simulated rural atmospheric boundary layer in a wind tunnel. The model obstacles covered a range of heights, widths, depths, and roof pitches typical of rural buildings. A field experiment was conducted using three unique full scale obstacles to validate model predictions and wind tunnel measurements. The accuracy of the neural network model varies with the quantity predicted and position in the obstacle wake. In general, predictions of mean velocity deficit in the far wake region are most accurate. The overall estimated mean uncertainties associated with model predictions of normalized mean wind speed and turbulence intensity are 4.9% and 12.8%, respectively.

• Journal of agriculture & life science
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• v.44 no.5
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• pp.101-107
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• 2010

The objective of this study was to assess the statistics and associated criteria for field-scale model used to simulate nutrient concentrations in paddy field. CREAMS-PADDY, a modified version of the field-scale CREAMS model, simulates the hydrologic, sediment, and nutrient cycles in paddy fields was applied in this study. The model was calibrated and validated using data from study rice paddy fields in Republic of Korea. The calibration statistics include mean and the minimum-maximum range associated with a "temporal window" that spans a period of several days. Because nutrient concentrations in paddy filed are typically sampled infrequently (on a weekly basis, at best) and represent only an instant in time, it is not reasonable to expect any model to simulate a daily average concentration equal to an observed value on a particular day. The 5-day window and related calibration statistics were applied in this study and the applicability of this concept was tested for field-scale water quality model. As a result of calibration and validation, the ponded water nutrient concentration values showed only small changes except the fertilization period. Because of the small changes in ponded water concentration, the size of 5-day window was too small to capture the observed values. Further study is required to establish the 5-day window calibration method for field-scale water quality modeling.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.56-63
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• 2017

Hydrogen charging station was invested and supported around the world. In this study, the extent of damage caused by VCE in the charging station handling liquefied hydrogen was calculated, and the human and material damage was estimated through the Probit model. In addition The optimal height of vent stack for low temperature hydrogen was set. The damage range is 8.24m in small scale, 14.10m in medium scale, and 22.38m in large scale based on interest overpressure 6.9kPa. In case of death due to pulmonary hemorrhage, 50m of the small and medium scale and 100m of the large scale were injured. Structural damage was 200m in small scale, 300m in medium scale and 500m in large scale. The optimum height of the vent stack is 4.7 m in small scale, 8.8 m in medium scale and 16.9 m in large scale.