• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.531-546
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• 2011

The backward differentiation formula (BDF) method is applied to a three-dimensional reactor kinetics calculation for efficient yet accurate transient analysis with adaptive time step control. The coarse mesh finite difference (CMFD) formulation is used for an efficient implementation of the BDF method that does not require excessive memory to store old information from previous time steps. An iterative scheme to update the nodal coupling coefficients through higher order local nodal solutions is established in order to make it possible to store only node average fluxes of the previous five time points. An adaptive time step control method is derived using two order solutions, the fifth and the fourth order BDF solutions, which provide an estimate of the solution error at the current time point. The performance of the BDF- and CMFD-based spatial kinetics calculation and the adaptive time step control scheme is examined with the NEACRP control rod ejection and rod withdrawal benchmark problems. The accuracy is first assessed by comparing the BDF-based results with those of the Crank-Nicholson method with an exponential transform. The effectiveness of the adaptive time step control is then assessed in terms of the possible computing time reduction in producing sufficiently accurate solutions that meet the desired solution fidelity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.734-740
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• 2001

In this paper the stress intensity factor under uniform pressure in the arbitrarily-shaped plane crack configuration transformed elliptic crack by Mobius mapping are determined. Using Dysons formula Boussinesq-Papkovich potentials for mode I deformation are constructed. In the example the stress intensity factors are approximately calculated by least square method.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.117-122
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• 2000

In this paper the stress intensity factor under uniform pressure in the arbitrarily-shaped plane crack configuration transformed elliptic crack by Mobius mapping are determined. Using Dyson's formula Boussinesq-Papkovich potentials for mode I deformation are constructed. In the example the stress intensity factors are approximately calculated by least square method.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1409-1414
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• 2013

A new calculation method for iron loss coefficients is proposed by using the Steinmetz equation from Epstein data. The hysteresis loss must have linear characteristic according to the frequency. However, the existing iron loss coefficients are defined by formula of frequency. In this case, the hysteresis loss has non-linear characteristics by frequency. So, in this paper, the iron loss coefficients were defined by a function of the magnetic flux density, and the iron loss calculation is applied for Interior Permanent Magnet Synchronous Motor(IPMSM) of 600(W) and 200(W). The iron loss calculation results and the experimental results are compared according to the various materials.

• Journal of Yeungnam Medical Science
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• v.32 no.2
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• pp.90-97
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• 2015

Background: Contrast-induced nephropathy (CIN) can cause serious adverse effects. To reduce the occurrence of CIN related computed tomography (CT) in emergency patients, we assessed the respective roles of serum creatinine (SCr) alone and estimated glomerular filtration rate (eGFR) as an early predictor for CIN related CT. Methods: For patients with SCr <1.5 mg/dL who underwent CT in emergency department (ED) between September 2012 and October 2013, we assessed the prevalence of CIN and its adverse effects. The Modification of Diet in Renal Disease Study (MDRD) and Cockcroft-Gault (CG) formula was used for the calculation of eGFR. Practical calculation was performed by electronic medical record (EMR) system for MDRD and internet calculating service for CG. And we investigated the prevalence of CIN in eGFR $<60mL/min/1.73m^2$ before CT. Results: A total of 1,555 patients were enrolled. The prevalence of CIN after CT was 4.6% and it showed correlation with renal deterioration, increased in-hospital mortality, and prolonged hospitalization. Despite baseline SCr <1.5 mg/dL, among enrolled patients, 11.3% as MDRD equation and 29.5% as CG formula were $<60mL/min/1.73m^2$ and in this condition, the prevalence of CIN was significantly high (odds ratio was 2.87 [1.64-5.02] as MDRD equation and 2.03 [1.26-3.29] as CG formula). Conclusion: Just SCr <1.5mg/dL was not appropriate to recognize preexisting renal insufficiency, but eGFR using MDRD equation was useful in predicting the risk of CIN related CT in ED. Using EMR, calculation of eGFR can be easier and more convenient.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.78-91
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• 2024

Double steel plate concrete composite shear wall (SCSW) has been widely utilized in nuclear power plants and high-rise structures, and its shear connectors have a substantial impact on the seismic performance of SCSW. Therefore, in this study, the mechanical properties of SCSW with angle stiffening ribs as shear connections were parametrically examined for the reactor containment structure of nuclear power plants. The axial compression ratio of the SCSW, the spacing of the angle stiffening rib arrangement and the thickness of the angle stiffening rib steel plate were selected as the study parameters. Four finite element models were constructed by using the finite element program named ABAQUS to verify the experimental results of our team, and 13 finite element models were established to investigate the selected three parameters. Thus, the shear capacity, deformation capacity, ductility and energy dissipation capacity of SCSW were determined. The research results show that: compared with studs, using stiffened ribs as shear connectors can significantly enhance the mechanical properties of SCSW; When the axial compression ratio is 0.3-0.4, the seismic performance of SCSW can be maximized; with the lowering of stiffener gap, the shear bearing capacity is greatly enhanced, and when the gap is lowered to a specific distance, the shear bearing capacity has no major affect; in addition, increasing the thickness of stiffeners can significantly increase the shear capacity, ductility and energy dissipation capacity of SCSW. With the rise in the thickness of angle stiffening ribs, the improvement rate of each mechanical property index slows down. Finally, the shear bearing capacity calculation formula of SCSW with angle stiffening ribs as shear connectors is derived. The average error between the theoretical calculation formula and the finite element calculation results is 8% demonstrating that the theoretical formula is reliable. This study can provide reference for the design of SCSW.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.965-974
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• 2009

The current study reviews the formula used to calculate the stability of an artificial reef in the breaking wave zone of coastal waters. A comparison was carried out between the existing formula and a new formula that takes into account the water particle velocity in the breaking wave zone. Water particle velocity was analyzed using the Fluent (CADMAS-SURF) software program. The new formula took into various factors, including the difference in the drag coefficient due to the direction of the current and the ratio of distance between two reefs. The drag coefficient of the artificial reef due to the direction of the current was 0.84 when the distance ratio was 0.5. When the artificial reef was placed at 45 degree angle to the current, the product of the drag coefficient and the project area were 40 to 46 % greater than when the reef was placed at 90 degree angle. Our results regarding the stability of an artificial reef indicate that the new formula provides the designers of artificial reefs with a more rational and economic design rationale rather than the existing formula.

• Journal of Korean Home Economics Education Association
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• v.23 no.3
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• pp.121-138
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• 2011

This research examined the amounts and methods change of recommended energy intake(REI) from 1962's recommended dietary intakes for Korean to 2010's dietary reference intakes for Koreans. REI is composed of 3 factors, such basal metabolic rate(or Resting Energy Expenditure, REE), activity energy, and thermogenic effect of foods. The first 1962 calculation formula of REI was weight based formula, that of 95's was the weight based REE multiplied by activity coefficient, and the recent one of 2005's(Estimated Energy Requirement: EER) was age, height. weight, and the activity level applying formula derived from the energy expenditure data by doubly labeled water technique(DLW). During the 50 years or so, REIs were reduced in all age groups, according to the activity(labor) strength and hour were reduced. The individual REI calculation method was introduced in 1995, and individual REI calculation was recommended since to prevent obesity. For the better REI estimation for Koreans, REI calculation formula derived from our peoples' DLW energy expenditure data is required.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.216-220
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• 1989

Direct calculation algorithm for the elements of A matrix is suggested for a single machine connected to the infinite bus. Excitation system and power system stabilizer are included. When A matrix is partitioned into seven submatrices, we can identify the location of non-zero elements and formula for each element. No matrix inversion and multiplication are necessary.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.411-416
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• 2002

This paper is concerned with the development of web-based engineering calculation program using Javascript. Recently, various techniques are developed based on the advance of the internet environment. The Javascript can be used in the client PC without any interpreter which is necessary in Java. Simple formula can be easily constructed using the Javascript and the results can be readily available without any playing. In this study, we demonstrated the method of constructing engineering web useful for engineers.