Attenuation Formula Research Articles

Expansion of Blast Vibration Attenuation Equations for Deeply Buried Small Clearance Tunnels Based on Dimensional Analysis

The conventional empirical Sadowski formula has low prediction accuracy for the vibration velocity of the mass point in the near zone of the blast source, which makes it challenging to evaluate the damage of the building structures accurately. Considering the main influencing factors of blast vibration, the blast vibration attenuation law of deeply buried small clearance tunnels is investigated using dimensional analysis, and the Sadowski expansion formula is established considering the resistance line and free face. The regression analysis and fitting results were evaluated by combining the actual blast vibration data measured at the excavation site of the three separated tunnels at Badaling Great Wall Station with the post-expansion formula and the Sadowski formula, respectively. The results show that the correlation coefficients of the blast vibration expansion formulae based on the gauge theory for the fitted predictions of blast vibration isotropic velocities in a practical engineering context (0.92, 0.81, and 0.88, respectively) are higher than those of the conventional attenuation formulae, by 12, 10.5, and 6.3%, respectively, indicating that the expanded Sadowski formulae can better predict the blast vibration attenuation generated by the described deeply buried small clearance tunneling project.

Dynamic response characteristics of adjacent tunnel lining under blasting impact in subway connecting passage

The connecting passage between two adjacent tunnels is conducive to the rescue and evacuation of subway tunnels when disasters occur. The blasting method is usually used in the construction of connecting passage. The vibration caused by blasting construction may endanger the safety of subway tunnel structure. As a result, the influence of blasting pressure on the stability of subway tunnel lining structure during the excavation of connecting passage is studied, and the safe blasting construction distance is proposed, which is crucial to the safety of adjacent subway tunnel lining. This study takes the connecting passage of Wuhan Metro Line 8 as an example. Using Finite element software ANSYS/LS-DYNA, an accurate numerical calculation model of construction site is established. The nonlinear elastoplastic mechanical characteristics of soil, rock, and tunnel lining are simulated by Drucker Prager, Plastic Kinematic, and Johnson Holmquist Concrete constitutive material models, respectively. The credibility of the three-dimensional numerical calculation model and material constitutive model was proved by contrasting the field measured data of the connecting passage with the numerical calculated results. Analysis of numerical results, the axial and radial PPV, frequency, and Von Mises stress of subway tunnel lining are obtained. The influence of subway tunnel lining under adjacent blasting can be obtained by analyzing the distribution law of PPV and Von Mises stress. Non-static tensile strength is needed considering the high pressure and high strain rate process of concrete during blasting. By fitting the relationship between PPV and dynamic tensile stress, and referring to DIF parameters, the safety range of PPV in subway tunnel lining blasting is determined. The critical safety distance between blasting construction and tunnel lining is obtained by Sadovsky vibration velocity attenuation formula, which is used to guide the subsequent blasting excavation of continuous tunnels.

Experiments on the characteristics of a sewage water source heat pump system for heat recovery from bath waste

• This non-metallic heat exchanger has better corrosion resistance. • The thermal conductivity of this non-metallic material is higher than that of traditional non-metallic heat exchangers. • The heat transfer coefficient of the nonmetal heat exchanger is less than that of the metal heat exchanger. • The heat exchanger in the sewage tank at different depths affects the adhesion rate of stains on the surface of the device, which is mainly caused by the different water flow rates. • Sewage heat recovery system plays an important role in energy saving and environmental protection. Sewage water source heat pump (SWSHP) systems with energy saving and environmental protection advantages have been widely studied, and sewage heat exchangers are an important part of SWSHP systems. Problems such as scale formation, difficulty in cleaning, and rapid decrease of their heat transfer coefficient with time have long been associated with SWSHP systems. With these in mind, in this study, we build a SWSHP system for the recovery of heat from waste using a waste water bath experimental platform, and applied a new, rare earth element (REE) non-metallic immersion sewage heat exchanger, The heat exchanger has heat transfer ability in actual working condition, as well as the operational features of a SWSHP system. From test data, the attenuation of heat transfer and the heat transfer coefficient of the sewage heat exchanger with time were analyzed. An attenuation formula of the heat transfer coefficient was determined using a logistic function. The results show that during 90 days of continuous operation, the surface heat transfer capacity decreased by approximately 7.8%, and the rate of decline over time was much lower than that of traditional heat exchangers. The results show that the system can produce hot water at 40.4–60.6 ℃, and the highest system coefficient of performance (SCOP) of the system is 5.65. Our study shows that varying the depth of immersion of the heat exchanger in the water pool affects the heat transfer ability of the heat exchanger. Results show that when the heat exchanger is closer to the pool surface, water-flushing action is strong. With a long runtime, the heat exchanger’s heat transfer ability has a slower rate of decline over time. Based on the test results, the energy consumption of the system was analyzed, and the energy saved by the continuous operation of the system for one year was determined to be equivalent to that of burning 4.29 × 10 4 kg of standard coal.

Determination of the Forward Electromagnetic Coupling Radius in Chaff Cloud

Chaff cloud is a passive jammer that is widely used in many tactical applications. It contains huge numbers of metallic fibers to produce a strong echo. However, electromagnetic (EM) scattering estimation for the chaff cloud is a challenging task since complex EM coupling between chaff elements needs to be taken into account. Actually, if the distance and the angle between two chaff elements are large enough, the EM coupling becomes ignorable. This letter presents an estimation method of the EM coupling radius to designate a region, out of which EM coupling effect can be ignored. A current attenuation formula is first proposed to indicate the relationship between the induced surface currents of any two chaff elements. Using Dijkstra's algorithm, we then find the coupling paths with the weakest attenuation. The EM coupling radius is finally determined by measuring the distance between two ends of the selected paths. Simulation results show that the averaged EM coupling radius is 3.7 times wavelength of the radar in our discussions.

Distance and position estimation in visible light systems with RGB LEDs

In this paper, distance and position estimation problems are investigated for visible light positioning (VLP) systems with red-green-blue (RGB) light emitting diodes (LEDs). The accuracy limits on distance and position estimation are calculated in terms of the Cramér-Rao lower bound (CRLB) for three different scenarios. Scenario 1 and Scenario 2 correspond to synchronous and asynchronous systems, respectively, with known channel attenuation formulas at the receiver. In Scenario 3, a synchronous system is considered but channel attenuation formulas are not known at the receiver. The derived CRLB expressions reveal the relations among distance/position estimation accuracies in the considered scenarios and lead to intuitive explanations for the benefits of using RGB LEDs. In addition, maximum likelihood (ML) estimators are derived in all scenarios, and it is shown that they can achieve close performance to the CRLBs in some cases for sufficiently high source optical powers.

Evaluation method on seismic risk of substation in strong earthquake area

Frequent earthquakes in strong earthquake areas pose a great threat to the safety operation of electric power facilities. There exists a pressing research need to develop an assessment method for the seismic risk of substations, i.e., the hubs of power system networks. In this study, based on Incremental Dynamic Analysis (IDA), Probabilistic Seismic Demand Model (PSDM) and reliability theory, a vulnerability model for a substation is obtained, based on considering the relationships between Peak Ground Acceleration (PGA) and four seismic damage states (complete, extensive, moderate, and slight.) via a probabilistic approach. After an earthquake, the scope of influence and PGA distribution are evaluated using information recorded by the seismic observation stations, based on using interpolation or an empirical formula for the PGA attenuation. Therefore, the seismic risk can be evaluated by combining ground motion evaluation and the pre-built vulnerability model. The Wuqia- Kashgar area of Xinjiang was selected as the study area; it is an Earthquake-prone area, and one of the starting points for new energy transmission projects in China. Under a hypothetical earthquake (MS 7.9), the seismic risk of the substations was evaluated. The results show that: this method is able to give the probabilities of the four damage states of the substations, four substations close to the epicenter only have a probability of slight damage (45%-88%) and other substations are safer.

Distribution of peak ground acceleration in Pandeglang Regency, Banten

Pandeglang Regency is an area prone to earthquakes because in the subduction zone of the Indo-Australian plate and the Eurasian plate in the Sunda Strait. This study analyses the average and maximum values of the Peak Ground Acceleration (PGA) got from earthquakes in the period 2000 to 2020 around Pandeglang Regency with the calculation method. Gutenberg-Richter with the Richter formula combined with the intensity attenuation formula which is a function of magnitude, epicentre distance, and earthquake intensity. From the maximum PGA data, the lowest value is 273 gals, and the highest is 427.5 gals. Meanwhile, for the distribution of the average PGA value, the minimum value is 54 gals, and the maximum value is 67 gals. From the PGA data, the maximum distribution of the highest PGA value is in the center of Pandeglang Regency, and the lowest value of the PGA maximum is in the northern and southern parts of Pandeglang Regency. The PGA value is potentially damaging at the VII MMI scale, where the area with the highest vulnerability is in the sub-district Angsana, Munjul, Panimbang, and Sidangresmi with the highest PGA scores, so this sub-district has the highest risk than other districts.

Influence of 3D printing stress wave on residual stress

As a popular rapid manufacturing technology, three-dimensional printing (3D printing) has been widely adopted in medical, automotive, aerospace, construction and other industrial fields. The stereo lithography apparatus (SLA) is an effective 3D printing method for ceramic printing. However, shrinkage from monomer to polymer and laser stress wave cause residual stress in the formed parts during SLA. Serious quality defects including cracks, warpage and deformation caused by residual stress have remained to be a problem. Basically, the laser stress wave plays an important role in the generation of 3D printing residual stress. In this work, to investigate the propagation mechanism of the laser stress wave, the finite element method was adopted to simulate the SLA process of zirconia. The influence of 3D printing factors on the residual stress was obtained, and we found that the wave velocity of the stress wave obtained by the simulation model was highly consistent with the theoretical wave velocity. Meanwhile, the attenuation formula of the stress wave in the 3D printing process was obtained by fitting to investigate its attenuation law. Based on the above results, the attenuation law of the 3D printing stress wave has a direct influence on the development and variation trend of its residual stress.

Long period ground motion simulation and its application to the seismic design of high-rise buildings

Increasing attention is being paid to the adverse effects of long period ground motion (LPGM) on high-rise buildings. However, it is hard to quantitatively define this special ground motion in seismic design, especially in the cases of regions in which sufficient seismic observations have not been made. To this end, this paper proposes an innovative LPGM simulation method. This method not only involves probabilistic seismic hazard analysis (PSHA), but also overcomes the limitations of the original empirical relation-based method. Firstly, a large number of data taken from typical sedimentary basins are utilized to determine the basin amplification factor model, by which an improved response spectra attenuation formula is developed based on the site amplification mechanisms in different periods. Then, based on the statistical regression analysis of the basin correction factors, the modified group delay time empirical formula is obtained. Furthermore, the conventional PSHA model is refined to determine the scenario earthquake. Finally, the design LPGM is generated by the phase difference spectrum method and its impact on high-rise buildings is embodied via a case study. The satisfactory result proves that the proposed method can effectively simulate LPGM and may have great potential in practice.

Coverage Analysis of Reconfigurable Intelligent Surface Assisted THz Wireless Systems

This paper presents a connectivity analysis of reconfigurable intelligent surface (RIS) assisted terahertz (THz) wireless systems. Specifically, a system model that accommodates the particularities of THz band links as well as the characteristics of the RIS is reported, accompanied by a novel general end-to-end (e2e) channel attenuation formula. Based on this formula, we derive a closed-form expression that returns the optimal phase shifting of each reflection unit (RU) of the RIS. Moreover, we provide a tractable e2e channel coefficient approximation that is suitable for analyzing the RIS-assisted THz wireless system performance. Building upon the aforementioned approximation as well as the assumption that the user equipments are located in random positions within a circular cluster, we present the theoretical framework that quantifies the coverage performance of the system under investigation. In more detail, we deliver a novel closed-form expression for the coverage probability that reveals that there exists a minimum transmission power that guarantees 100% coverage probability. Both the derived channel model as well as the coverage probability are validated through extensive simulations and reveal the importance of taking into account both the THz channel particularities and the RIS characteristics, when assessing the system's performance and designing RIS-assisted THz wireless systems.

Optimising the Preparedness Capacity of Enterprise Resilience Using Mathematical Programming

In today’s volatile business arena, companies need to be resilient to deal with the unexpected. One of the main pillars of enterprise resilience is the capacity to anticipate, prevent and prepare in advance for disruptions. From this perspective, the paper proposes a mixed-integer linear programming (MILP) model for optimising preparedness capacity. Based on the proposed reference framework for enterprise resilience enhancement, the MILP optimises the activation of preventive actions to reduce proneness to disruption. To do so, the objective function minimizes the sum of the annual expected cost of disruptive events after implementing preventive actions and the annual cost of such actions. Moreover, the algorithm includes a constraint capping the investment in preventive actions and an attenuation formula to deal with the joint savings produced by the activation of two or more preventive actions on the same disruptive event. The management and business rationale for proposing the MILP approach is to keep it as simple and comprehensible as possible so that it does not require highly mathematically skilled personnel, thus allowing top managers at enterprises of any size to apply it effortlessly. Finally, a real pilot case study was performed to validate the mathematical formulation.

Study on the Vibration Effect of Short Footage Blasting Load on Surrounding Rock-Support Structure of Tunnel

In the excavation process of a drilling and blasting tunnel, it takes multiple blasting excavations to form, so it is inevitable to produce multiple blasting impact loads, which will cause certain vibration damage to the surrounding rock-support structure. To solve this problem, based on the attenuation formula of blasting vibration wave and considering the cumulative effect of short footage blasting load, the radial displacement formula of surrounding rock particles is derived, and the analytical solution of vibration velocity field is obtained by using the method of separating variables. Then, taking Cuobuling station of Qingdao Metro as the engineering background, the finite element software is used to simulate the tunnel excavation process under the action of short footage multiple blasting. The vibration damage impact of multiple blasting loads on the surrounding rock-supporting structure is analyzed from the accumulated displacement value and vibration velocity cumulative value of the excavation tunnel. The results show that the damage accumulation effect is produced in the surrounding rock of each section during the blasting construction, among which the accumulation is the largest at the arch bottom. With the increase of blasting times, the damage of the surrounding rock is still accumulating gradually. Compared with the first blasting, the peak value of vibration velocity of the second blasting increased by 114%, and with the increase of blasting times, the variation trend of maximum vibration velocity of the measuring point showed an upward trend, but the subsequent vibration acceleration decreased. Under the condition of grade V surrounding rock, when the thickness of the concrete spray layer is 350 mm, the maximum displacement cumulative value of each measuring point in profile 1-1 is reduced by about 50.4% compared with that without support. According to the displacement nephogram of the concrete spray layer, the displacement of the concrete spray layer accumulates after three times of blasting, which affects the stability of the supporting structure. Finally, an example analysis is carried out and compared with the analytical model results to verify the accuracy of the mechanical model.

Examination of phenomenological formulae in superdeformed bands of A ∼ 190,150 mass regions

The rotational energy formulae viz. VMI model, ab-formula, Harris [Formula: see text] expansion, Exponential model with pairing attenuation and Nuclear softness formula are employed to the superdeformed bands of [Formula: see text] and [Formula: see text] mass regions in order to test the validity of various rotational energy formulae in describing the general nature of superdeformed bands. These formulae are used to deduce the band-head spins of the nine superdeformed bands in [Formula: see text] mass region and two superdeformed bands of [Formula: see text] mass region. The band-head spins of these superdeformed bands have been established experimentally and hence they prove to be excellent candidates to examine the adequacy of rotational energy formulae in superdeformed bands. The least-squares fitting of [Formula: see text]-transition energies is performed to calculate the model parameters such as the band-head moment of inertia, the effective pairing gap parameter and the softness parameter, and a careful analysis of these parameters is made. For the first time, we have performed a systematic study of the rotational energy formulae to establish which formula gives the best estimate of spin in [Formula: see text] mass regions.

Influence of Blasting Vibrations Generated by Tunnel Construction on an Existing Road

Tunnel excavations are commonly carried out using the drill and blast method, which may cause blast-induced damage to adjacent buildings. Peak particle velocity (PPV) is a widely used parameter for evaluating the damage of blasting vibration. However, accurately predicting PPV is difficult with traditional empirical predicting methods because their results are often different from actual conditions. In this study, attenuation formula of propagation velocity of elastic stress waves in elastomer is derived on the basis of stress wave theory. Moreover, the formula for predicting PPV is modified in the case of multihole and multistage blasting and then applied to Guanlinzi Tunnel, which downtraverses through National Highway 316. Results show that the modified formula obtains a small relative error between predicted and in situ monitoring PPVs and can properly reflect the propagation law of PPV under the condition of multihole and multistage blasting. This work has important application prospects and can provide a reference for similar excavation blasting and vibration control methods.

Calculation of Beam Hardening in Industrial X-ray Computed Tomography and its Correction using Filtration and Linearization Methods

X-ray computed tomography is becoming an instrument for quality assurance as nondestructive testing for product inspection in industrial applications. However, the systematic error in the XCT image resulting from the physical processes of image reconstruction must be corrected. Beam hardening is one of the major artefacts that come due to an extensive range of photon energies in common x-ray sources in computed tomography instrument so-known polychromatic X-rays. The polychromatic can cause a nonlinear relationship between the attenuation and the thickness. As a result, the reconstructed image seems to have some darkness in the centre, which is considered a significant decreasing of the image quality. In this work the calculations of beam hardening and its correction using filtration and linearization methods were described. The calculations were done in four stages: the GEANT4 code was used for spectrum simulation; an optimum filter materials and thickness was chosen by a mean energy ratio method; the attenuation of aluminium material was numerically calculated using the basic polychromatic attenuation formulas, and the beam hardening was corrected using linearization and compared with the filtration method. The calculated polychromatic attenuations results of aluminium were found to be in good agreement with the existing literature. The linearization correction offers better beam hardening correction which gave a good linearity estimation without changing SNR when compared with the pre-filtration method.

Определение параметров исторических землетрясений по макросейсмическим данным

The paper attempts to determine the main parameters of historical earthquakes of the Carpathian region based on macroseismic data, using the macroseismic field equation, indirect parameters, and complex comparison with modern earthquakes. So far, the main source of information about the parameters of historical earthquakes in the Carpathian region has been "New catalog of strong earthquakes ...". In this catalog, all parameters are defined very ap-proximately, with a wide range of values. In addition, over the forty-year period since the release of the catalog, the initial macroseismic data of Carpathian region earthquakes have been substantially replenished and re-evaluated using the MSK-64 macroseismic scale. The study determined such basic parameters of historical earthquakes as the macroseismic epicenter, the intensity at the epicenter, focal depth, and magnitude. As well as additional parameters: direction of the maximum macro-seismic effect, area of intensity zones, distance, and azimuth to the extreme point where the earthquake was felt. The earthquake parameters were calculated using the attenuation formula of the macroseismic field with coefficients obtained by the R.Z. Burtiev for intermediate earthquakes of the Vrancea zone of the Carpathian region, separately in four azimuthal ranges. For crustal earthquakes, the general Blake-Shebalin macroseismic field equation was used. Despite possible errors associated with a correct assessment of intensity at observation points, as well as the accuracy of the coefficients of the macro-seismic field equation used for specific seismic events, it was possible to determine the type of each historical earthquake and obtain more accurate values of their parameters. The re-fined parameters of historical earthquakes will allow making a more holistic picture of the seismic hazard in the Carpathian region.

Two life prediction models for optoelectronic displays without conventional life tests.

To precisely predict the life of optoelectronic displays over a short time, two life prediction models were established based on the three-parameter Weibull right approximation method (TPWRAM). In Model I, the acceleration life under each stress was obtained using TPWRAM, the data points formed by acceleration life and acceleration stress were, respectively, fitted by three extrapolation functions and the optimal extrapolation function was determined by comparing the fitting determination coefficient and root-mean-square error. In Model II, after introducing an acceleration parameter, the luminance attenuation data under conventional stress were calculated directly by combining the ones obtained using TPWRAM under each acceleration stress. The luminance attenuation test data from the vacuum fluorescent display (VFD) were collected through four groups of constant-stress accelerated degradation tests (ADT), and the two models were applied to the life prediction of VFD. The results indicated that the designed ADT scheme was feasible, Model I revealed the changing law of life with stress and simplified the process of life prediction, and Model II made it possible to obtain the luminance attenuation formula at conventional stress without conducting a conventional life test, overcoming the shortcomings of long time-consuming traditional life tests. It was verified by comparing the life prediction values that the two models had very high precision, and both of these not only achieve the accurate estimation of optoelectronic product life without resorting to conventional life test, but also improved the method of life prediction and perfect its theoretical system.

Enterprise Resilience Assessment—A Quantitative Approach

Enterprise resilience is a key capacity to guarantee enterprises’ long-term continuity. This paper proposes a quantitative approach to enhance enterprise resilience by selecting optimal preventive actions to be activated to cushion the impact of disruptive events and to improve preparedness capability, one of the pillars of the enterprise resilience capacity. The proposed algorithms combine the dynamic programming approach with attenuation formulas to model real improvements when a combined set of preventive actions is activated for the same disruptive event. A numerical example is presented that shows remarkable reductions in the expected annual cost due to potential disruptive events.

Evaluation of capability of blast-induced ground vibration predictors considering measurement distance and different error measures

This study aims to investigate capability of the vibration prediction approaches, comprehensively. Field investigations were performed in a sandstone quarry. All the main conventional scaled distance equations were evaluated. A multivariate equation that contains blast design parameters was created by stepwise regression. A robust artificial neural network model was constructed. Effect of the additional parameters on success of the vibration estimation was examined. The success of the equations was evaluated considering the measurement distance. Evaluation of vibrations based on the measurement distance provided an opportunity to examine effectiveness of the equations that contains inelastic attenuation factor. Suitable error measures were investigated to examine the precision of vibration estimation. Both percentage errors and symmetric errors were found to be useful. Increase in the measurement distance was resulted in increase in prediction error. The classical scaled distance equations were found to be quite successful. The multivariate equation and artificial neural network model did not made better predictions than the scaled distance equations for long distance. The equations with inelastic attenuation formula do not have any advantage over classical scaled distance equations.

Numerical simulation of the blast wave of a multilayer composite charge

Abstract The numerical simulation of a blast wave of a multilayer composite charge is investigated. A calculation model of the near-field explosion and far-field propagation of the shock wave of a composite charge is established using the AUTODYN finite element program. Results of the near-field and far-field calculations of the shock wave respectively converge at cell sizes of 0.25–0.5 cm and 1–3 cm. The Euler––flux-corrected transport solver is found to be suitable for the far-field calculation after mapping. A numerical simulation is conducted to study the formation, propagation, and interaction of the shock wave of the composite charge for different initiation modes. It is found that the initiation mode obviously affects the shock-wave waveform and pressure distribution of the composite charge. Additionally, it is found that the area of the overpressure distribution is greatest for internal and external simultaneous initiation, and the peak pressure of the shock wave exponentially decays, fitting the calculation formula of the peak overpressure attenuation under different initiation modes, which is obtained and verified by experiment. The difference between numerical and experimental results is less than 10%, and the peak overpressure of both internal and external initiation is 56.12% higher than that of central single-point initiation.