• Bulletin of the Korean Chemical Society
• /
• 제10권2호
• /
• pp.142-147
• /
• 1989

Fluorescence enhancements of ethidium bromide (EB) by solution species of low molecular weights such as DNA base molecules and nucleosides in water are reported. The degree of enhancements was determined by intensity as well as lifetime measurements for EB fluorescence. Experiments including solvent effects on absorbance and fluorescence spectra of EB, effects of protonation on the EB absorbance spectrum, and determination of equilibrium constants for EB-DNA bases have been performed to help explain the fluorescence enhancement. The results suggest that the excited state stabilization in the hydrophobic environment, the loss of torsional/vibrational energy of amino groups, and the change in the electronic transition characteristics are all responsible for the fluorescence enhancement.

• 한국공간구조학회논문집
• /
• 제13권1호
• /
• pp.79-86
• /
• 2013

For most of recent tall buildings, one characteristic is that their building shapes vary with height such as taper and setback, and this implies that the distribution of their structural components may also vary with height. Because of these structural variations, although the sectional shapes of these buildings are symmetric, it is difficult to say whether or not they are structurally symmetric. The acceleration responses of structurally asymmetric tall buildings are larger than those of non-eccentric buildings, thus raising the possibility of problems during strong winds and typhoons. This paper describes wind tunnel tests carried out using building models with height variations and acceleration response analyses, and discusses the resulting response characteristics. For tapered and setback buildings, although the across-wind accelerations are larger than those of a square building, the total root-mean-square accelerations remain small because of smaller along-wind and torsional rms accelerations. And it was found that the effects of statistical couplings between along-wind force and other two forces are negligible.

• 한국자동차공학회논문집
• /
• 제16권4호
• /
• pp.135-142
• /
• 2008

Hydraulic power steering system has been adopted in seniority passenger and commercial vehicle system for an easy maneuverability and a smoother ride. In this study, hydraulic power steering system analysis model which includes hydraulics and mechanical sub-systems was developed using commercial software, AMESim in order to predict characteristics for various steering components. Each component which constructs system was modeled and verified by experimentally obtained characteristics curves of each components. The parameter sensitivity analysis such as valve opening area, torsional stiffness of torsion bar for system design are carried out by the analysis and experimental method. The predicted results by the development model were a good agreement with experimentally obtained results. The sensitivity investigation results rotary torque when changing an input shaft edge width, was most sensitive, to change in angle and slot width and supply flow of input shaft edge is not a lot sensitively.

• Smart Structures and Systems
• /
• 제15권6호
• /
• pp.1439-1461
• /
• 2015

Design criteria, modeling rules, and analysis principles of seismic isolation systems have already found place in important building codes and standards such as the Uniform Building Code and ASCE/SEI 7-05. Although real behaviors of isolation systems composed of high damping or lead rubber bearings are nonlinear, equivalent linear models can be obtained using effective stiffness and damping which makes use of linear seismic analysis methods for seismic-isolated buildings possible. However, equivalent linear modeling and analysis may lead to errors in seismic response terms of multi-story buildings and thus need to be assessed comprehensively. This study investigates the accuracy of equivalent linear modeling via numerical experiments conducted on generic five-story three dimensional seismic-isolated buildings. A wide range of nonlinear isolation systems with different characteristics and their equivalent linear counterparts are subjected to historical earthquakes and isolation system displacements, top floor accelerations, story drifts, base shears, and torsional base moments are compared. Relations between the accuracy of the estimates of peak structural responses from equivalent linear models and typical characteristics of nonlinear isolation systems including effective period, rigid-body mode period, effective viscous damping ratio, and post-yield to pre-yield stiffness ratio are established. Influence of biaxial interaction and plan eccentricity are also examined.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.515-520
• /
• 2005

The behavior of jointed rock mass is much different from that of intact rock due to the presence of joints. Similarly, the characteristics of elastic wave propagation in jointed rock are considerably different from those of intact rock. The propagation of elastic waves in jointed rock is greatly dependent on the state of stress. The roughness, filling materials, and spacing of joints also affect wave propagation in jointed rock. If the wavelength of elastic waves is much larger than the spacing between joints, wave propagation in jointed rock mass can be considered as wave propagation in equivalent continuum. A rock resonant column testing apparatus is made to measure elastic waves propagating through jointed rock in the state of equivalent continuum. Three types of wave, i.e, torsional, longitudinal and flexural waves are monitored during rock resonant column tests. Various roughness and filling materials are applied to joints, and rock columns with various spacings are used to understand how these factors affect wave propagation under a small strain condition. The experimental results suggest that the characteristics of wave propagation in jointed rock mass are governed by the state of stress and influenced by roughness, filling materials and joint spacings.

• Smart Structures and Systems
• /
• 제19권5호
• /
• pp.523-538
• /
• 2017

A series of field vibration tests are conducted on the Runyang Suspension Bridge during both the construction and operational stages. The purpose of this study is devoted to the analysis of the dynamic characteristics of the suspension tower. After the tower was erected, an array of accelerometers was deployed to study the evolution of its modal parameters during the construction process. Dynamic tests were first performed under the freestanding tower condition and then under the tower-cable condition after the superstructure was installed. Based on the identified modal parameters, the effect of the pile-soil-structure interaction on dynamic characteristics of the suspension tower is investigated. Moreover, the stiffness of the pile foundation is successfully identified using a probabilistic finite model updating method. Furthermore, challenges of identifying the dynamic properties of the tower from the coupled responses of the tower-cable system are discussed in detail. It's found that compared with the identified results from the freestanding tower, the longitudinal and torsional natural frequencies of the tower in the tower-cable system have changed significantly, while the lateral mode frequencies change slightly. The identified modal results from measurements by the structural health monitoring system further confirmed that the vibrations of the bridge subsystems (i.e., the tower, the suspended deck and the main cable) are strongly coupled with one another.

• Structural Engineering and Mechanics
• /
• 제37권3호
• /
• pp.297-307
• /
• 2011

Meck Plot is an adapted version of the well-known Southwell method to the case of lateral-torsional buckling, which indeed reflects the physical inter-dependence of lateral flexure (lateral displacement) and torsion (rotation) in the structure. In the recent reported studies, it has been shown experimentally and theoretically that lateral displacement of an I-beam undergoing elastic lateral-distortional mode of buckling is interestingly directly coupled with other various deformation characteristics such as web transverse strain, web longitudinal strain, vertical deflection, and angles of twist of top and bottom flanges, and consequently good results have been obtained as a result of application of the Meck's method on lateral displacement together with each of the aforementioned deformation variables. In this paper, it is demonstrated that even web transverse and longitudinal strains, vertical deflection, and angles of twist of top and bottom flanges of an I-beam undergoing elastic lateral-distortional buckling are two-by-two directly coupled and the application of the Meck Plot on each pair of these deformation variables may still yield reliable predictions for the critical buckling load.

• 국제초고층학회논문집
• /
• 제2권3호
• /
• pp.213-228
• /
• 2013

Tall buildings have been traditionally designed to be symmetric rectangular, triangular or circular in plan, in order to avoid excessive seismic-induced torsional vibrations due to eccentricity, especially in seismic-prone regions like Japan. However, recent tall building design has been released from the spell of compulsory symmetric shape design, and free-style design is increasing. This is mainly due to architects' and structural designers' challenging demands for novel and unconventional expressions. Another important aspect is that rather complicated sectional shapes are basically good with regard to aerodynamic properties for crosswind excitations, which are a key issue in tall-building wind-resistant design. A series of wind tunnel experiments and numerical simulation have been carried out to determine aerodynamic forces and wind pressures acting on tall building models with various configurations: corner cut, setbacks, helical and so on. Dynamic wind-induced response analyses of these models have also been conducted. The results of these experiments have led to comprehensive understanding of the aerodynamic characteristics of tall buildings with various configurations.

• Steel and Composite Structures
• /
• 제10권4호
• /
• pp.297-315
• /
• 2010

This paper is concerned with free vibration characteristics and natural frequency of horizontally curved composite plate girder bridges. Three-dimensional finite element models are developed for the girders using the software package LUSAS and analyses carried out on the models. The validity of the finite element models is first established through comparison with the corresponding results published by other researchers. Studies are then carried out to investigate the effects of total number of girders, number of cross-frames and curvature on the free vibration response of horizontally curved composite plate girder bridges. The results confirm the fact that bending modes are always coupled with torsional modes for horizontally curved bridge girder systems. The results show that the first bending mode is influenced by composite action between the concrete deck and steel beam at low subtended angle but, on the girders with larger subtended angle at the centre of curvature such influence is non-existence. The increase in the number of girders results in higher natural frequency but at a decreasing rate. The in-plane modes viz. longitudinal and arching modes are significantly influenced by composite action and number of girders. If no composite action is taken into account the number of girders has no significant effect for the in-plane modes.

• Nuclear Engineering and Technology
• /
• 제51권2호
• /
• pp.546-555
• /
• 2019

Since the first nuclear reactor first critical, nuclear systems has gone through four generations of history, and the fourth generation nuclear system will be truly realized in the near future. The notions of SVBR and lead-bismuth eutectic alloy coolant put forward by Russia were well received by the international nuclear science community. Lead-bismuth eutectic alloy with the ability of the better neutron economy, the low melting point, the high boiling point, the chemical inertness to water and air and other features, which was considered the most promising coolant for the 4th generation nuclear reactors. This study mainly focuses on the structural design optimization of the 4th-generation reactor coolant pump, including analysis of external characteristics, inner flow, and transient characteristic. It was found that: the reactor coolant pump with a central symmetrical dual-outlet volute structure has better radial-direction balance, the pump without guide vane has better hydraulic performance, and the pump with guide vanes has worse torsional vibration and pressure pulsation. This study serves as experience accumulation and technical support for the development of the 4th generation nuclear energy system.