• Structural Engineering and Mechanics
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• 제44권2호
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• pp.127-138
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• 2012

The composite materials may be exposed to environmental (thermal or hygral or both) condition during their service life. The effect of environmental condition is usually adverse from the point of view of design of composite structures. In the present research study the effect of hygrothermal condition on the design of laminated composite structures is investigated. The active fiber composite (AFC) which may be utilized as actuator or sensor is considered in the present analysis. The sensor layer is used to sense the level of response of the composite structures. The sensed voltage is fed back to the actuator through the controller. In this study both displacement and velocity feedback controllers are employed to reduce the response of the composite laminate within acceptable limit. The Newmark direct time integration scheme is employed along with modal superposition method to improve the computational efficiency. It is observed from the numerical study that the laminated composite structures become weak in the presence of hygrothermal load. The response of the structure can be brought to the acceptable level once the AFC layer is activated through the feedback loop.

• Computers and Concrete
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• 제6권6호
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• pp.505-521
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• 2009

The analysis of prismatic members made of reinforced concrete under inclined bending, especially the computation of ultimate loads, is a pronounced non-linear problem which is frequently solved by discretizing the stress distribution in the cross-section using interpolation functions. In the approach described in the present contribution the exact analytical stress distribution is used instead. The obtained expressions are integrated by means of a symbolic manipulation package and automatically converted to optimized Fortran code. The direct problem-computation of ultimate internal forces given the position of the neutral axis-is first described. Subsequently, two kinds of inverse problem are treated: the computation of rupture envelops and the dimensioning of reinforcement, given design internal forces. An iterative Newton-Raphson procedure is used. Examples are presented.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권8호
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• pp.482-492
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• 2002

This paper deals with overvoltage stresses in the field circuit of synchronous machine connected to HVDC terminal. A load rejection of the HVDC may cause generator in the station to become self-excited, resulting in a severe system overvoltage. This paper shows that violent field current oscillations can be produced by resonance between the machine inductance and the terminal capacitance. As most conventional excitation system do not allow reverses current, new topology of excitation system to allow reverse current is proposed. the proposed system can limit the rate of rise of terminal voltage during conditions of self excitation. Apart from these simulations, the nature(Magnitude and frequency) of the field transient state is explained mathematically. Finally, the EMTDC program is used for the simulation studies.

• Nuclear Engineering and Technology
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• 제13권4호
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• pp.229-236
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• 1981

중성자포획 감마선 방사화분석법을 이용하여 원자로급 알루미늄중 붕소를 분석하였다. 실험에 의한 검출한계는 10% 불확실도의 경우 5.7ppm 이었다. 함량이 더욱 미량인 경우를 위하여 양이온 교환수지를 이용하며 알루미늄으로 부터 붕소를 사전분리하는 농축법을 개발하였다. 이 두 방법 즉 직접 측정하는 방법과 농축후 측정하는 두가지 방법의 정확도를 첨가법으로 조사하였다. 그 결과 5% 편차 이내에서 잘 일치하였다.

• Nuclear Engineering and Technology
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• 제19권4호
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• pp.242-248
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• 1987

레이저를 이용한 형광분석 방법과 형광의 세기를 증대시켜주는 'Fluran' 용액을 가함으로써 용액속에 존재하는 미량의 우라늄을 정착하고 신속하게 분석할 수 있는 새로운 장치를 개발하였다. 표준용액의 첨가 방법을 이용하여 시료의 조성 변화에 따른 형광의 방해효과를 보정할 수 있었고 5%이내의 정밀도를 갖는 0.1ppb의 측정 하한치를 얻을 수 있었다. 또한 여러 종류의 시료에 대하여 레이저를 이용한 형광분석 방법의 결과와 다른 측정 방법에 의한 결과를 상호 비교, 분석하였다.

• Steel and Composite Structures
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• 제6권2호
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• pp.103-122
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• 2006

The capacity of tubular truss chords subjected to concentrated reaction forces in the vicinity of the open end (i.e., the bearing region) is not directly treated by existing design specifications; although capacity equations are promulgated for related tubular joint configurations. The lack of direct treatment of bearing capacity in existing design specifications seems to represent an unsatisfactory situation given the fact that connections very often control the design of long-span tubular structures comprised of members with slender cross-sections. The case of the simple-span overhead highway sign truss is studied, in which the bearing reaction is applied near the chord end. The present research is aimed at assessing the validity of adapting existing specifications' capacity equations from related cases so as to be applicable in determining design capacity in tubular truss bearing regions. These modified capacity equations are subsequently used in comparisons with full-scale experimental results obtained from testing carried out at the University of Pittsburgh.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.198-201
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• 1999

An optimal cooling method for HTS(high Tc superconductor) current leads has been analytically sought to minimize the required refrigerator power. The binary current lead is a series combination of a normal metal conductor at the warmer part and an HTS at the colder part. The lead is cooled by direct contacts with a two-stage cryocooler at the joint and at the cold end. It is clearly proven that there exists unique optimal values for the joint temperature and the current density to minimize the refrigerator power per unit current. the actual power input to the cryocooler in the optimal conditions is compared with its thermodynamic limit, and some significant issues in practical design are presented with a useful graphical method.

• 천문학회보
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• 제37권1호
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• pp.47.1-47.1
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• 2012

Given high accretion rates close to the Eddington limit, narrow-line Seyfert 1 galaxies (NLS1) are arguably the most important AGN subclass in investigating the origin of the black hole mass-galaxy stellar velocity dispersion ($M_{BH}-{\sigma}$) relation. Currently, it is highly debated whether NLS1s are offset from the local $M_{BH}-{\sigma}$ relation. The controversy mainly comes from the fact that the [OIII] line width has been used as a proxy for stellar velocity dispersion due to the difficulty of measuring stellar velocity dispersion in NLS1s. Using the SDSS spectra of a sample of 105 NLS1, we performed multi-component fitting analysis to separate stellar absorption lines from strong AGN [FeII] complex in order to directly measure stellar velocity dispersion. We will present the result of decomposition analysis and discuss whether NLS1s follow the same $M_{BH}-{\sigma}$ relation based on the direct measurements of stellar velocity dispersion.

• Journal of applied mathematics & informatics
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• 제4권1호
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• pp.147-166
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• 1997

The convergence of the power sequence of an $n{\times}n$ fuzzy matrix has been studied. Some theoretical necessary and sufficient con-ditions have been established for the power sequence to be convergent generally. Furthermore as one of our main concerns the convergence index was studied in detail especially for some special types of Boolean matrices. Also it has been established that the convergence index is bounded by $(n-1)^2+1$ from above for an arbitrary $n{\times}n$ fuzzy matrix if its power sequence converges. Our method is concentrated on the limit behavior of the power se-quence. It helped us to make our proofs be simpler and more direct that those in pure algebraic methods.

• Food Science and Biotechnology
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• 제15권6호
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• pp.990-992
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• 2006

In a previous study, we obtained polyclonal antibodies against the organophosphorus insecticide fenitrothion and developed an enzyme-linked immunosorbent assay (ELISA) for this pesticide. Using these antibodies and an enzyme tracer, a direct competitive ELISA method specific for fenitrothion using a dipstick format was developed. Dipstick ELISA using antibodies to fenitrothion immobilized on an Immunodyne membrane allowed the quick visual detection of fenitrothion at concentrations above $10\;{\mu}g/L$. The $IC_{50}$ value of dipstick ELISA using reflectance detection was $27\;{\mu}g/L$ with a detection limit of $2\;{\mu}g/L$. The recovery of fenitrothion from spiked lettuce and rice samples using the dipstick ELISA ranged from 87-107%.