• Smart Structures and Systems
• /
• v.16 no.3
• /
• pp.383-399
• /
• 2015

Today, as railways increase their capacity and speeds, it is more important than ever to be completely aware of the state of vehicles fleet's condition to ensure the highest quality and safety standards, as well as being able to maintain the costs as low as possible. Operation of a modern, dynamic and efficient railway demands a real time, accurate and reliable evaluation of the infrastructure assets, including signal networks and diagnostic systems able to acquire functional parameters. In the conventional system, measurement data are reliably collected using coaxial wires for communication between sensors and the repository. As sensors grow in size, the cost of the monitoring system can grow. Recently, auto-powered wireless sensor has been considered as an alternative tool for economical and accurate realization of structural health monitoring system, being provided by the following essential features: on-board micro-processor, sensing capability, wireless communication, auto-powered battery, and low cost. In this work, an original harvester device is designed to supply wireless sensor system battery using train bogie energy. Piezoelectric materials have in here considered due to their established ability to directly convert applied strain energy into usable electric energy and their relatively simple modelling into an integrated system. The mechanical and electrical properties of the system are studied according to the project specifications. The numerical formulation is implemented with in-house code using commercial software tool and then experimentally validated through a proof of concept setup using an excitation signal by a real application scenario.

• Geomechanics and Engineering
• /
• v.13 no.5
• /
• pp.715-742
• /
• 2017

Earth berms are often left in place to support retaining walls or piles in order to eliminate horizontal struts in excavations of soft soil areas. However, if the excavation depth is relatively large, an earth berm-supported retaining system may not be applicable and could be replaced by a multi-bench retaining system. However, studies on multi-bench retaining systems are limited. The goal of this investigation is to study the deformation characteristics, internal forces and interaction mechanisms of the retaining structures in a multi-bench retaining system and the failure modes of this retaining system. Therefore, a series of model tests of a two-bench retaining system was designed and conducted, and corresponding finite difference simulations were developed to back-analyze the model tests and for further analysis. The tests and numerical results show that the distance between the two rows of retaining piles (bench width) and their embedded lengths can significantly influence the relative movement between the piles; this relative movement determines the horizontal stress distribution in the soil between the two rows of piles (i.e., the bench zone) and thus determines the bending moments in the retaining piles. As the bench width increases, the deformations and bending moments in the retaining piles decrease, while the excavation stability increases. If the second retaining piles are longer than a certain length, they will experience a larger bending moment than the first retaining piles and become the primary retaining structure. In addition, for varying bench widths, the slip surface formation differs, and the failure modes of two-bench retained excavations can be divided into three types: integrated failure, interactive failure and disconnected failure.

• Smart Structures and Systems
• /
• v.19 no.1
• /
• pp.1-10
• /
• 2017

The operation of subway trains induces secondary structure-borne vibrations in the nearby underground spaces. The vibration, along with the associated noise, can cause annoyance and adverse physical, physiological, and psychological effects on humans in dense urban environments. Traditional tethered instruments restrict the rapid measurement and assessment on such vibration effect. This paper presents a novel approach for Wireless Smart Sensor (WSS)-based autonomous evaluation system for the subway train-induced vibrations. The system was implemented on a MEMSIC's Imote2 platform, using a SHM-H high-sensitivity accelerometer board stacked on top. A new embedded application VibrationLevelCalculation, which determines the International Organization for Standardization defined weighted acceleration level, was added into the Illinois Structural Health Monitoring Project Service Toolsuite. The system was verified in a large underground space, where a nearby subway station is a good source of ground excitation caused by the running subway trains. Using an on-board processor, each sensor calculated the distribution of vibration levels within the testing zone, and sent the distribution of vibration level by radio to display it on the central server. Also, the raw time-histories and frequency spectrum were retrieved from the WSS leaf nodes. Subsequently, spectral vibration levels in the one-third octave band, characterizing the vibrating influence of different frequency components on human bodies, was also calculated from each sensor node. Experimental validation demonstrates that the proposed system is efficient for autonomously evaluating the subway train-induced ambient vibration of underground spaces, and the system holds the potential of greatly reducing the laboring of dynamic field testing.

• Journal of the Korean Society for Library and Information Science
• /
• v.25
• /
• pp.151-183
• /
• 1993

As many Korean libraries has begun to be automated and become a part of the worldwide, open library system, they need a new management. Therefore, the purpose of this paper is to explore the library management in automated libraries and to establish a theory of the library management in information society, The automated libraries could be well explained by the systems theory and the environment of the libraries could be well explained by the contingency theory, The following hypothesis were set to direct this research. 1. As the libraries are automated and become a part of one big, worldwide library system, the libraries interact closely with the environment so that the library and the environment become one. 2. As the libraries are automated and become a part of one big, worldwide library system, the librarians need to work in the environment for the library networks, standardization of cataloging, or government information policy making. 3. As the libraries are automated and become a part of one big, worldwide library system, the librarians only manage the library, The various other library staffs take over the traditional library services directly related to books. The data were gathered from the research done previously, Also the date were collected from the American and Japanese libraries. The findings were as follows: The environment of the library integrated all types of the library services such as school library, university library, etc. And it also integrated all the services of the media centers and the press centers, etc. to library services. And the new library services began in the environment. Librarians worked for these new services. In the library, the librarians distingushed the library system from the environment by planning : mission, goal, objectives, policy, procedures and rules. Library organization became temporary such as forming task forces or matrix or free form. The environment controlled the library. Staffs were controlled by plans or computers. And the professional librarians were controlled by their ability to solve problems raised outside the libraries. Library leaders brought in the technology to the library from its environment. The librarians led the formal and informal organizations so that the staffs cooperated well in their work. And librarians tought the library procedures to the partime workers or the temporary staffs. Participative management and management by objectives were the means of motivating staffs. Budget was based on the ever changing environment. The zero based budget method was applied. Therfore, in the information society, the professional librarians become the able managers in the library and global librarians in the environment.

• Korean Security Journal
• /
• no.6
• /
• pp.195-213
• /
• 2003

This is a case study on the violent collective activities of spectators in professional soccer games. The purpose of this study is to examine the reasons and the processes of the activities. In order to achieve the purpose well, I analyzed two cases of violent collective activities in spectators of professional soccer games that were held on June 24 and July 28 in 2001. The data for this study was collected from 14 kinds of daily newspapers from June 10 to August 20 in 2001 to maintain the objective validity of the outline, the reasons, and the processes of the violent collective activities of spectators in two cases. The data was collected from Korea Integrated News Database System(KINDS) of Korea Press Foundation, and Chollian, on-line service of DACOM, for its efficiency, accuracy and promptness. On the basis of the above-mentioned method as well as the consequences of data analysis, I've reached to a conclusion as follows. The reasons of the violent collective activities of spectators in professional soccer games were the mass effect, the activities of players, umpires and the results of games, etc. The violent collective activities of spectators in professional soccer games need pre-requirements and have relationships with special affairs that are developed in a regular sequence. In other words, a collective activity gives an effect on another one directly or indirectly. Therefore, this study shows that we can reduce or prevent the damages by the violent collective activities of spectators in sport games when we analyze the processes of collective activities and make a previous counter-measure for that.

• Structural Engineering and Mechanics
• /
• v.49 no.2
• /
• pp.203-223
• /
• 2014

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.

• Membrane and Water Treatment
• /
• v.5 no.1
• /
• pp.15-29
• /
• 2014

Reverse Osmosis (RO) desalination has gained wide and increasing acceptance around the world as a straightforward undertaking to alleviate the alarming water crisis. An enhanced monitoring of the quality of the water feeding in seawater RO (SWRO) plant through the application of an effective pretreatment option is one of the keys to the success of RO technology in desalination plants. Over the past 10 years, advances in ultrafiltration (UF) membrane technologies in application for water and wastewater treatment have prompted an impetus for using membrane pretreatment in seawater desalination plants. By integrating SWRO plant with UF pretreatment, the rate of membrane fouling can be significantly reduced and thus extend the life of RO membrane. With the growing importance and significant advances attained in UF pretreatment, this review presents an overview of UF pretreatment in SWRO plants. The advantages offered by UF as an alternative of pretreatment option are compared to the existing conventionally used technologies. The current progress made in the integration of SWRO with UF pretreatment is also highlighted. Finally, the recent advances pursued in UF technology is reviewed in order to provide an insight and hence path the way for the future development of this technology.

• Smart Structures and Systems
• /
• v.3 no.2
• /
• pp.201-217
• /
• 2007

An active damage detection technique is introduced to locate damage in an isotropic plate using Lamb waves. This technique uses a time-domain energy model of Lamb waves in plates that the wave amplitude inversely decays with the propagation distance along a ray direction. Accordingly the damage localization is formulated as a least-squares problem to minimize an error function between the model and the measured data. An active sensing system with integrated actuators/sensors is controlled to excite/receive $A_0$ mode of Lamb waves in the plate. Scattered wave signals from the damage can be obtained by subtracting the baseline signal of the undamaged plate from the recorded signal of the damaged plate. In the experimental study, after collecting the scattered wave signals, a discrete wavelet transform (DWT) is employed to extract the first scattered wave pack from the damage, then an iterative method is derived to solve the least-squares problem for locating the damage. Since this method does not rely on time-of-flight but wave energy measurement, it is more robust, reliable, and noise-tolerant. Both numerical and experimental examples are performed to verify the efficiency and accuracy of the method, and the results demonstrate that the estimated damage position stably converges to the targeted damage.

• Steel and Composite Structures
• /
• v.6 no.1
• /
• pp.15-31
• /
• 2006

Beams with web openings are an attractive system for multi-storey buildings where it is always desirable to have long spans. The openings in the web of steel beams enable building services to be integrated within the constructional depth of a floor, thus reducing the total floor depth. At the same time, the increased beam depth can give high bending moment capacity, thus allowing long spans. However, almost all of the research studies on web openings have been concentrated on beam behaviour at ambient temperature. In this paper, a preliminary numerical analysis using ABAQUS is conducted to develop a general understanding of the effect of the presence of web opening on the behaviour of steel beams at elevated temperatures. It is concluded that the presence of web openings will have substantial influence on the failure temperatures of axially unrestrained beams and the opening size at the critical position in the beam is the most important factor. For axially restrained beams, the effect of web openings on the beam's large deflection behaviour and catenary force is smaller and it is the maximum opening size that will affect the beam's response at very high temperatures. However, it is possible that catenary action develops in beams with web openings at temperatures much lower than the failure temperatures of the same beam without axial restraint that are often used as the basis of current design.

• Earthquakes and Structures
• /
• v.18 no.3
• /
• pp.297-312
• /
• 2020

The KiK-net by NIED is a vertical array measurement system. In the database of KiK-net, singular pulse waves were observed in the seismic record at the borehole of TTRH02 during the mainshock (the magnitude of Japan Meteorological Agency (M_J) 7.3, M_W 6.8) and aftershock (M_j 4.2) of Tottori-ken Seibu earthquake in 2000. Singular pulse waves were also detected in the seismic records at the borehole of IWTH25 during the Iwate-Miyagi Nairiku earthquake in 2008 (M_J 7.2, M_W 6.9). These pulse waves are investigated by using the wave shape analysis methods, e.g., the non-stationary Fourier spectra and the double integrated displacement profiles. Two types of vibration modes are discriminated as the occurrence mechanism of the singular pulse waves. One corresponds to the reversal points in the displacement profile with the amplitude from 10^-4 m to 10^-1 m, which is mainly related to the fault activity and the amplification pass including the mechanical amplification (collision) of the seismograph in the casing pipe. The other is the cyclic pulse waves in the interval of reversal points, which is estimated as the backlash of the seismograph itself with the amplitude from 10^-5 m to 10^-4 m.