Ground Vibrational Level Research Articles

Comparative kinetic analysis of isothermal extraction of caffeine from guarana seed under conventional and microwave heating

The kinetics of the isothermal extraction of caffeine from the guarana seed powder with water under conventional (CH) and microwave heating (MWH) were investigated. By applying the isoconversional method, it was established that the kinetics of the caffeine extraction under CH and also under MWH is an elementary kinetic process. The model fitting method was used to determine the kinetics model of caffeine extraction. It was found that the kinetics of the caffeine extraction for both heating modes can be described by the Jander’s equation. The rate of the extraction of caffeine under MWH is ∼2 times higher than under CH. The values of kinetics parameters (Ea and lnA) of the extraction process under MWH are lower than for CH. The established influence of MWH on the kinetics of caffeine extraction is explained with a specific activation mechanism of water molecules and with an increase in the energy of the ground vibration level of resonant oscillator of N3–CH3 band of caffeine molecule (ν=317cm−1) which is caused by the absorption of microwave energy.

GROUND VIBRATIONS LEVEL CHARACTERIZATION THROUGH THE GEOLOGICAL STRENGTH INDEX (GSI)

This paper analyses the results of trial, construction and quarry blasting, carried out in sediment rock deposits, mainly limestone and dolomite, at diff erent locations in the Republic of Croatia. The division of the three test groups was based on the lithology changes and GSI values of the rock units at these locations. The peak particle velocity measurements with 246 recorded events, was conducted during a long period of six years. Based on the results of seismic measurements, the empirical relationships between peak particle velocity and scaled distance were established for each group. In order to establish a useful relationship between peak particle velocity and scaled distance, simple regression analysis was conducted with the Blastware software program from Instantel. The results of this study can be used to characterize ground vibration levels to the environment, through the geological strength index (GSI).

Isolation of residential buildings from ground vibration from railroad

For residential developments near railroad tracks, ground vibration due to train movement is often a concern. Although there are usually no code requirements for vibration levels, ground vibration levels are often compared to the criteria recommended by the FTA; these criteria are sometimes explicitly included as part of the Conditions of Approval or other governing documents required for the development of the site. These criteria are often exceeded when the development is in proximity to the tracks, but experience has provided limited practical applications for reducing the vibration. Some of the methods suggested include isolating the building on elastomeric bearings, digging a wave barrier trench, increasing the mass of the foundation, and stiffening the joist structure. However, these measures have been rarely employed, and little data are available on the objective effects of the mitigation, correlated with the benefit to occupants. Despite this, such methods are sometimes required on a project without analysis of efficacy or even an understanding of the anticipated result. The authors have compiled the results of recent measurements on several buildings that employed some these measures, and discuss the benefits of the mitigation measures and their application to building construction strategy.

Measurements of a wave barrier trench for isolation of rail vibration

Where buildings are adjacent to railroad tracks, one option for reducing levels of ground vibration is to dig a trench between the tracks and the project to act as a wave barrier. The application of this method has been rare within the United States, and consequently, practical experience is very limited. On a recent project of the authors, a wave barrier trench was constructed [Dong and LoVerde, JASA 139, 2159 (2016)]. Measurements have been performed is various conditions both before and after construction of the trench. The vibration insertion loss was measured and compared to theory, and recommendations based on the experience are provided. This paper extends the analysis with additional information and data.

The effect of embankment on high speed rail ground vibrations

ABSTRACTThis paper presents the numerical prediction of ground vibration levels on embankmented high speed rail lines. First, a campaign of field tests is described, focused on the three-dimensional (3D) monitoring of ground vibration on at-grade and embankmented tracks. Next, a finite element (FE) model is developed to study the detailed earthwork geometries. The model is validated and then used to investigate the effect of embankment stiffness on ground vibration levels both within and at distance from the track-embankment structure. It is found that ground vibration levels are sensitive to embankment stiffness, with stiffer embankments resulting in greatly reduced vibration levels. Further, it is found that in general, well constructed embankmented tracks generate lower levels of ground vibration in comparison to at-grade lines.

Radially and temporally resolved electric field of positive streamers in air and modelling of the induced plasma chemistry

The initial stages of transient luminous events (TLEs) occurring in the upper atmosphere of the Earth are, in a certain pressure range, controlled by the streamer mechanism. This paper presents the results of the first laboratory experiments to study the TLE streamer phenomena under conditions close to those of the upper atmosphere. Spectrally and highly spatiotemporally resolved emissions originating from radiative states (second positive system) and (first negative system) have been recorded from the positive streamer discharge. Periodic ionizing events were generated in a barrier discharge arrangement at a pressure of 4 torr of synthetic air, i.e. simulating the pressure conditions at altitudes of ≃37 km. Employing Abel inversion on the radially scanned streamer emission and a 2D fitting procedure, access was obtained to the local spectral signatures within the over 106 m s−1 fast propagating streamers. The reduced electric field strength distribution within the streamer head was determined from the ratio of the band intensities with peak values up to 500 Td and overall duration of about 10 ns. The 2D profiles of the streamer head electric fields were used as an experimentally obtained input for kinetic simulations of the streamer-induced air plasma chemistry. The radial and temporal computed distribution of the ground vibrational levels of the radiative states involved in the radiative transitions analyzed (337.1 nm and 391.5 nm), atomic oxygen, nitrogen, nitric oxide and ozone concentrations are vizualized and discussed in comparison with available models of the streamer phase of Blue Jet discharges in the stratosphere.

Measurements of the reduction in ground vibration levels from wave barrier trench

Where buildings are adjacent to railroad tracks, there are limited practical applications for controlling the transmission of train vibration. In critical listening spaces like auditoria or government buildings, isolation of the building structure is sometimes undertaken. However, this option is not attractive for most commercial or residential development due to the attendant costs and complications. For these properties, one option for reducing levels of ground vibration is to dig a trench between the tracks and the project to act as a wave barrier. Construction of a deep trench presents a wide variety of construction challenges, and the application of this method has been rare within the United States due to the lack of regulations and sensitivity that might demand such an approach. The authors recently had a project where a wave barrier (trench) was applied, which provided the opportunity to observe the construction of the trench and to measure the resulting reduction in ground vibration levels before and after the installation. Various aspects of this process are discussed.

Rovibrationally Excited Molecules on the Verge of a Triple Breakdown: Molecular and Roaming Mechanisms in the Photodecomposition of Methyl Formate.

For the photodissociation of the simplest of esters, methyl formate HCOOCH3, the energy threshold for triple fragmentation into H, CH3O, and CO was measured by previous ion-imaging experiments at a sequence of wavelengths. The translational energy features of product CO in the ground vibrational level (υ = 0) and for selected rotational states were characterized. In this integrated experimental and theoretical approach (i) the focus is at a laser energy barely below that threshold; (ii) Fourier-transform infrared emission spectroscopy measurements probe the rovibrational energy deposition in CO(υ) for υ > 0 and the emergence of the roaming phenomenon; (iii) accompanying quantum chemical calculations describe the selective rupture of bonds; and (iv) molecular dynamics simulations of dissociation are performed, introducing an approach explicitly involving outcomes from paths originated nonadiabatically through conical intersections. Quantitative information on energy disposal is provided: we found extensive vibrational excitation of CO, while rotational bands are colder and bimodal, due to contributions from direct and roaming modes.

Non equilibrium vibrational assisted dissociation and ionization mechanisms in cold CO2 plasmas

Upper limits rates of pure vibrational dissociation mechanisms of CO2 in discharge and post discharge conditions have been compared with the direct electron impact rates from the ground vibrational level as well as including transitions from a multitude of vibrational states. At low reduced electric field E/N values and, mostly, in the post discharge regime (E/N=0), the pure vibrational rates exceed the corresponding ones from electron impact dissociation mechanisms, showing the importance of vibrational excitation in the dissociation of CO2.Comparison of ground vibrational state ionization rate with the corresponding one, which takes into account ionization transitions from excited vibrational levels, shows large difference in both discharge and post discharge conditions.The accuracy of the results largely depends on the number of vibrational levels included in the Boltzmann equation as shown by inserting, in the Boltzmann solver, all electron–vibration transitions involving the asymmetric vibrational levels of the CO2 molecule.

A Comparative Study of Ground and Underground Vibrations Induced by Bench Blasting

Ground vibrations originating from bench blasting may cause damage to slopes, structures, and underground workings in close proximity to an operating open-pit mine. It is important to monitor and predict ground vibration levels induced by blasting and to take measures to reduce their hazardous effects. The aims of this paper are to determine the weaker protection objects by comparatively studying bench blasting induced vibrations obtained at surface and in an underground tunnel in an open-pit mine and thus to seek vibration control methods to protect engineering objects at the site. Vibrations arising from measurement devices at surface and in an underground tunnel at the Zijinshan Open-Pit Mine were obtained. Comparative analysis of the peak particle velocities shows that, in the greatest majority of cases, surface values are higher than underground values for the same vibration distance. The transmission laws of surface and underground vibrations were established depending on the type of rock mass, the explosive charge, and the distance. Compared with the Chinese Safety Regulations for Blasting (GB6722-2014), the bench blasting induced vibrations would not currently cause damage to the underground tunnel. According to the maximum allowable peak particle velocities for different objects, the permitted maximum charges per delay are obtained to reduce damage to these objects at different distances.

저심도 터널과 인접한 방진벽의 지반진동 저감효과

본 논문에서는 계측자료와 해석방법의 조합에 의하여 지반진동을 평가하는 방법을 제시하였다. 평가방법의 기본개념은 FRA(Federal Railway Administration)에서 발간한 진동상세평가 매뉴얼에서 제시한 방법과 유사하나 구체적 평가방법은 다양한 유형의 방진벽의 진동저감 효과를 용이하게 평가할 수 있도록 수정되었다. 터널바닥에 작용하는 하중밀도(force density)는 해당선로의 차량 및 궤도조건을 잘 고려할 수 있는 차량-궤도 상호작용해석에 의하여 산정하였다. 지반진동의 전파유동성(transfer mobility) 2차원 지반진동해석을 통하여 평가하였다. 지반진동의 2차원 해석은 각 모델간의 상대비교에 있어서는 좋은 결과를 얻을 수 있으나 절대치 평가는 어렵다. 따라서 여기서는 사전에 계측된 자료와 해석결과의 비교를 통하여 실제 지반진동 전파특성을 반영할 수 있도록 계산된 전파유동성을 보완하였다. 정립된 진동평가방법을 적용하여 실제 진동민원문제가 크게 발생하였던 도시철도 저심도 터널구간을 대상으로 9가지 유형의 방진벽의 진동저감 효과를 분석하였다. This paper presents an assessment method of the ground vibration level with a combination of measured data and an analytic method. The basic concept of the method is similar to that in FRA(Federal Railway Administration) manual for detailed vibration analyses. However, going into detail, the assessment method was modified for a feasible evaluation of the vibration reduction effects of diverse types of wave barriers. The force density was evaluated in a vehicle-track interaction analysis and the transfer mobility of vibration was analyzed through a 2-D ground vibration analysis. The calculated 2-D transfer mobility was corrected to incorporate transfer characteristics of actual ground vibration by comparing the previously measured data and analysis results. Nine types of vibration reduction effects of wave barriers were analyzed on a shallow tunnel section of an urban railway where numerous civil complaints had actually been filed.

Airblast and Ground Vibration Monitoring at Chimiwungo Pit

Impacts of airblast and vibrations arise from blasting, a dangerous activity if not designed and performed to standard. This paper evaluates airblast and ground vibration levels and its potential impact on the neighbouring communities. Two calibrated seismographs were used to monitor potential airblast and ground vibration generated from the blast at Chimiwungo Pit. The blast complied with the set limits for infrastructures and slopes monitoring. Vibrations recorded from the trial shot PPV were predicted at 2.46 mm/s and Airblast of 10 mm/s with a maximum of 134 dB at the mine boundary, all remained well below accepted industry standards and guidelines. The airblast and ground vibration levels monitored and recorded were considered to be normal for surface blasting operations and had no negative impact on the nearby township of Manyama.

Attenuation of Pipe Ramming-Induced Ground Vibrations

AbstractPipe ramming installations generally induce high levels of ground vibrations that may affect the structural integrity of nearby buildings and utilities. This paper investigates the ground vibrations associated with pipe ramming installations and develops reliable models for estimating the ground vibration levels in an effort to avoid the undesirable effects of the vibrations. The study presents field observations of ground vibrations in which an open-ended steel casing 1,070 mm in diameter and 37 m long was driven into granular soils using two pneumatic hammers of varying energy. The ground vibrations observed during the installation are presented as a function of magnitude of peak particle velocity, frequency content, and direction of propagation. Observations indicate that a wide range of amplitudes and frequencies is possible, ranging from 1 to 100 mm/s and 20 to 100 Hz, respectively, for the case of forward and laterally propagating vibrations. The forward-propagating vibrations were observed...

Development and experimental validation of a numerical model for the prediction of ground vibration generated by pavement breaking

Pavement breakers are used to break rigid pavements and obtain a suitable foundation for new top layers or to enable pavement removal. The operation of falling weight pavement breakers generates high levels of ground vibration which is potentially damaging to nearby buildings and infrastructure. A numerical model for the prediction of ground vibration generated by pavement breaking is presented in this paper. First, the impact load due to a single blow of a falling weight pavement breaker is estimated by means of a simplified model of the hammer, the pavement, and the underlying soil. The predicted impact load is in good agreement with experimental results, which have been estimated from measured accelerations of one of the hammers of a pavement breaker. Second, the response of the pavement and the soil due to the impact load is considered. In order to account for inelastic soil behaviour and slab uplifting, a non-linear model of the coupled road-soil system is developed. Predictions of ground vibrations generated by the operation of a multi-head pavement breaker are validated by comparison with experimental results. A relatively good agreement is obtained between the results of the non-linear model and measured ground vibration. Comparison with results obtained with a linear model shows that disregarding non-linear phenomena leads to significant overestimation of the ground vibration levels close to the source, whereas similar results are obtained at larger distances.

State-Selective Excitation of Quantum Systems via Geometrical Optimization

We lay out the foundations of a general method of quantum control via geometrical optimization. We apply the method to state-selective population transfer using ultrashort transform-limited pulses between manifolds of levels that may represent, e.g., state-selective transitions in molecules. Assuming that certain states can be prepared, we develop three implementations: (i) preoptimization, which implies engineering the initial state within the ground manifold or electronic state before the pulse is applied; (ii) postoptimization, which implies engineering the final state within the excited manifold or target electronic state, after the pulse; and (iii) double-time optimization, which uses both types of time-ordered manipulations. We apply the schemes to two important dynamical problems: To prepare arbitrary vibrational superposition states on the target electronic state and to select weakly coupled vibrational states. Whereas full population inversion between the electronic states only requires control at initial time in all of the ground vibrational levels, only very specific superposition states can be prepared with high fidelity by either pre- or postoptimization mechanisms. Full state-selective population inversion requires manipulating the vibrational coherences in the ground electronic state before the optical pulse is applied and in the excited electronic state afterward, but not during all times.

Theoretical approach to the study of vibrational effects on strong field ionization of molecules with alignment-dependent tunneling ionization rates**Project supported by the National Basic Research Program of China (Grant No. 2013CB922200) and the National Natural Science Foundation of China (Grant Nos. 11034003 and 11127403).

The tunneling ionization rates of vibrationally excited N2 molecules at the ground electronic state are calculated using molecular orbital Ammosov–Delone–Krainov theory considering R-dependence. The results show that molecular alignment significantly affects the ionization rate, as the rate is mainly determined by the electron density distribution of the highest occupied molecular orbital. The present work indicates that the ratios of alignment-dependent rates of different vibrational levels to that of the vibrational ground level increase for the aligned N2 at the angle θ = 0°, and suggests that the alignment-dependent tunneling ionization rates can be used as a diagnostics for the influence of vibrational excitation on the strong field ionization of molecules.

Feasibility of indirect determination of blast induced ground vibration based on support vector machine

Mines, quarries, and construction sites face blasting environmental problems due to high level of ground vibrations. This phenomena can cause injury to both human and damage to structures in the blasting environment. To estimate ground vibration, several empirical predictors have been established by various researchers, while these predictors are not commonly enforceable beyond the particular conditions. However, ground vibration prediction is a complicated issue in consequence of the fact that a large number of influential factors are involved. In this study, a support vector machine (SVM) was applied and developed to predict ground vibration in blasting operations of Bakhtiari Dam, Iran. To achieve this aim, 80 blasting works were investigated and results of peak particle velocity (PPV) as a vibration index, distance from the blast-face and maximum charge per delay were measured and monitored to utilize in the modeling. To demonstrate applicability of the SVM model for prediction of PPV, several empirical equations were also employed and the relevant site constants were proposed. In the analyses procedure of this study, 60 datasets were used for model development and remaining 20 datasets were applied to check the performance capacity of the developed model. After comparing the results obtained from SVM and empirical equations, it was found that the SVM method provides higher performance capacity in predicting PPV compared to empirical equations.

Rotationally inelastic scattering of ND3 with H2 as a probe of the intermolecular potential energy surface

Differential cross sections (DCSs) are reported for rotationally inelastic scattering of ND3 with H2, measured using a crossed molecular beam apparatus with velocity map imaging (VMI). ND3 molecules were quantum-state selected in the ground electronic and vibrational levels and, optionally, in the j±k = 11− rotation-inversion level prior to collisions. Inelastic scattering of state-selected ND3 with H2 was measured at the mean collision energy of 580 cm−1 by resonance-enhanced multiphoton ionisation spectroscopy and VMI of ND3 in selected single final j'±k' levels. Comparison of experimental DCSs with close-coupling quantum-mechanical scattering calculations serves as a test of a recently reported ab initio potential energy surface. Calculated integral cross sections reveal the propensities for scattering into various final j'±k' levels of ND3 and differences between scattering by ortho and para H2. Integral and differential cross sections are also computed at a mean collision energy of 430 cm–1 and compared to our recent results for inelastic scattering of state-selected ND3 with He.

Railway ground vibrations induced by wheel and rail singular defects

Railway local irregularities are a growing source of ground-borne vibration and can cause negative environmental impacts, particularly in urban areas. Therefore, this paper analyses the effect of railway track singular defects (discontinuities) on ground vibration generation and propagation. A vehicle/track/soil numerical railway model is presented, capable of accurately predicting vibration levels. The prediction model is composed of a multibody vehicle model, a flexible track model and a finite/infinite element soil model. Firstly, analysis is undertaken to assess the ability of wheel/rail contact models to accurately simulate the force generation at the wheel/rail contact, in the presence of a singular defect. It is found that, although linear contact models are sufficient for modelling ground vibration on smooth tracks, when singular defects are present higher accuracy wheel/rail models are required. Furthermore, it is found that the variation in wheel/rail force during the singular defect contact depends on the track flexibility, and thus requires a fully coupled vehicle/track/foundation model. Next, a parametric study of ground vibrations generated by singular rail and wheel defects is undertaken. Six shapes of discontinuity are modelled, representing various defect types such as transition zones, switches, crossings, rail joints and wheel flats. The vehicle is modelled as an AM96 train set and it is found that ground vibration levels are highly sensitive to defect height, length and shape.

Dispersed Fluorescence Spectroscopy of Jet-Cooled 2-, 3-, and 4-Methylcyclohexoxy Radicals.

Vibrational structures of the nearly degenerate X̃ and à states of the 2-, 3-, and 4-methylcyclohexoxy (MCHO) radicals were studied by jet-cooled dispersed fluorescence (DF) spectroscopy. The observed transitions were assigned on the basis of vibrational frequencies and Franck-Condon factors predicted by quantum chemical calculations. Intensities of vibronic transitions in the DF spectra are dependent on the laser-induced fluorescence (LIF) bands pumped in the experiment, which can be explained by the difference in geometry and symmetry between the lower X̃/à states and the highly excited B̃ state. All three studied isomers of MCHO have close-lying X̃ and à states although their energy separations are affected by the position of the methyl group. It is suggested by quantum chemical calculations that the lowest-energy conformers of all three isomers have the half-filled orbital oriented perpendicular to the OCH plane, which is consistent with the observed relative intensities of the B̃ → X̃ and B̃ → à origin bands. When the origin and the CO-stretch bands of the B̃ ← X̃ LIF excitation spectra were pumped, the DF spectra were dominated by CO-stretch progressions. When non-CO-stretch vibrational levels of the B̃ state were pumped, progressions of CO-stretch modes combined with the pumped vibrational mode were observed. Excited-state vibrational population relaxation from the CO stretch level to the vibrational ground level and from combination levels of the CO stretch mode and other vibrational modes to the non-CO stretch modes was observed. Analysis of the DF spectra confirms the previous conclusion that all strong LIF bands observed under jet-cooled conditions belong to a single conformer of each positional isomer (Lin et al. RSC Adv. 2012, 2, 583-589).