Unveiling the power spectra of δ Scuti stars with TESS

Thanks to high-precision photometric data legacy from space telescopes like CoRoT and Kepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules: δ Scuti stars seem to be characterized with seismic indexes such as the large separation (Δν). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power (νmax) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of δ Scuti stars seem to be.

SEISMIC ASSESSMENT OF EXISTING BUILDING IN BANGLADESH USING JAPANESE INDEX METHOD

Over the years buildings are constructed in earthquake prone areas without following proper seismic design code. So the structural seismic analysis of existing buildings in the earthquake prone areas will be a prime requirement in the field of civil engineering in near future. Also the structural seismic analysis will lead to the feasibility of application of earthquake retrofitting technique in the vulnerable structures. Currently the urbanization of metropolitan cities in Bangladesh is booming rapidly leading these cities to densely populated area. In the past, there has been vulnerability assessment done for building stock on several metropolitan cities, in most cases using rapid visual screening (RVS) method. But the lacking has always been there on a detailed structural vulnerability assessment. Considering these facts a study has to be done to estimate precisely the possible damage of a building’s structure. In this study an in-depth structural seismic analysis of a medium rise building has been performed using all the 3 levels of Japanese Index Method. The Seismic Index (Is) value of the building is compared with the Seismic Demand Index (Iso) value which is 0.864 for the first level and 0.648 for the second and third level of the area to check vulnerability condition of the building structure. It is observed from this study that Japanese Index Method is developed in a way that it can be used for the seismic analysis of medium rise buildings in Bangladesh.

Evaluation Method for Seismic Fatigue Damage of Plant Pipeline

Although acceleration and cumulative absolute velocity (CAV) are used as seismic indexes, their relationship with the damage mechanism is not yet understood. In this paper, a simplified evaluation method for seismic fatigue damage, which can be used as a seismic index for screening, is derived from the stress amplitude obtained from CAV for one cycle in accordance with the velocity criterion in ASME Operation and Maintenance of Nuclear Power Plants 2012, and the linear cumulative damage due to fatigue can be obtained from the linear cumulative damage rule. To verify the performance of the method, the vibration response of a cantilever pipe is calculated for four earthquake waves, and the cumulative fatigue damage is evaluated using the rain flow method. The result is in good agreement with the value obtained by the method based on the relative response. When the response spectrum obtained by the evaluation method is considered, the value obtained by the evaluation method has a peak at the peak frequency of the ground motion, and the value decreases with increasing natural frequency above the peak frequency. A higher peak frequency of the base leads to a higher value obtained by the evaluation method.

Seismic performance

Context. Asteroseismology is a unique tool that can be used to study the interior of stars and hence deliver unique information for the studiy of stellar physics, stellar evolution, and Galactic archaeology. Aims. We aim to develop a simple model of the information content of asteroseismology and to characterize the ability and precision with which fundamental properties of stars can be estimated for different space missions. Methods. We defined and calibrated metrics of the seismic performance. The metrics, expressed by a seismic index ℰ defined by simple scaling relations, are calculated for an ensemble of stars. We studied the relations between the properties of mission observations, fundamental stellar properties, and the performance index. We also defined thresholds for asteroseismic detection and measurement of different stellar properties. Results. We find two regimes of asteroseismic performance: the first where the signal strength is dominated by stellar properties and not by observational noise; and the second where observational properties dominate. Typically, for evolved stars, stellar properties provide the dominant terms in estimating the information content, while main sequence stars fall in the regime where the observational properties, especially stellar magnitude, dominate. We estimate scaling relations to predict ℰ with an intrinsic scatter of around 21%. Incidentally, the metrics allow us to distinguish stars burning either hydrogen or helium. Conclusions. Our predictions will help identify the nature of the cohort of existing and future asteroseismic observations. In addition, the predicted performance for PLATO will help define optimal observing strategies for defined scientific goals.

Seismic performance evaluation of existing building using Seismic Index method

Indonesia has frequently suffered major damaging earthquakes over the past 50 years. There are thousands of buildings in earthquakeprone regions that require seismic evaluation and rehabilitation. This paper describes a study about the seismic evaluation of existing buildings using seismic index method based on a Japanese standard. The basic seismic index is calculated based on the criteria of strength and ductility. Two existing buildings have been evaluated in this research. The first building consists of five stories and the second one has four. The seismic index of the structure has a different value for each story. The minimum seismic index occurs on the ground floor, and the index increases as the number of stories increase. The top floor has the maximum seismic index of all stories. The structure’s seismic safety shall be judged if the seismic index (Is) is greater than the seismic demand index (Iso). As a result of the evaluation, buildings A, and B are in an unsatisfactory condition. Especially for the three lower floors of both of buildings. It is also confirmed by drift angle that they exceed the required limit. To sum up, evaluation by using Japanese standards can be applied to building conditions in Indonesia.

Evaluation Method for Seismic Fatigue Damage of Plant Pipeline

Although acceleration and cumulative absolute velocity (CAV) are used as seismic indexes, their relationship with the damage mechanism is not yet understood. In this paper, a simplified evaluation method for seismic fatigue damage, which can be used as a seismic index for screening, is derived from the stress amplitude obtained from CAV for one cycle in accordance with the velocity criterion in ASME Operation and Maintenance of Nuclear Power Plants 2012, and the linear cumulative damage due to fatigue can be obtained from the linear cumulative damage rule. To verify the performance of the method, the vibration response of a cantilever pipe is calculated for four earthquake waves, and the cumulative fatigue damage is evaluated using the rain flow method. The result is in good agreement with the value obtained by the method based on the relative response. When the response spectrum obtained by the evaluation method is considered, the value obtained by the evaluation method has a peak at the peak frequency of the ground motion, and the value decreases with increasing natural frequency above the peak frequency. A higher peak frequency of the base leads to a higher value obtained by the evaluation method.

Emergency Communication and Quick Seismic Damage Investigation Based on Smartphone

The communications in the quake-hit area are always cut off from the outside after the earthquake, and the traditional seismic field investigation method calls for immense time to accomplish house-to-house investigation, which goes against timeliness of the emergency rescue. In this paper, an emergency communication and quick seismic damage investigation method based on smartphone is proposed. Towards this, an application, E-Explorer, on iOS platform is initially developed. First, in the emergency communication module, the communication is available by using the Multipeer Connectivity Framework technology even without external network. A series of validation experiments are simulated without external network, and the results prove convincing. This module enhances the possibility of communication and increases the chances for rescue. Second, in the damage investigation module, E-Explorer integrates the functions of questionnaire and picture collection for damage phenomenon recording and image acquisition, following an intensity evaluation method according to seismic index. Last, a website, which provides guidance for rescue workers and collects damage information for quick intensity evaluation, is being built.

SEISMIC PERFORMANCE EVALUATION OF ASSEMBLED O-STABLE PANEL WALLS

O-Stable Panel is a new type of assembled structural wall. To evaluate the performance properties of the O-Stable Panel system, three integral prefabricated panel specimens with different vertical connections at the bottom and one full cast-in-place panel specimen were designed and tested under the low cycle lateral reciprocating loading. The performance of the prefabricated O-Stable Panel systems with different vertical connection configurations was compared with those of the full cast-in-place panel. The investigation reveals that all prefabricated O-Stable panel specimens developed vertical cracks penetrating through thickness of the panels at the panel joint and at the positions where panel thickness variation occurs at the ultimate failure state. The O-Stable panels possess the likely symmetric and stable hysteretic curves and no pinching appearance in shape of the curves. The panel with grouting sleeve in vertical joint for steel rebar appears sharp degrading in seismic index as the lateral drift of the wall increases beyond yield of the panel. For the assembled panel with preinstalled rebar stretched into the foundation beam for the vertical rebar joints, it has very close values in the hysteretic energy dissipation as that in the full cast-in-place panels.