Floor Configuration Research Articles

Lower and upper bounds for scheduling a real-life assembly problem with precedences and resource constraints

In this work, we consider a real-life scheduling problem involving the production of off-road vehicles using a three-level assembly process, subject to precedence, machines, and resource constraints. This problem shares multiple characteristics with other scheduling problems such as the Parallel Machine Scheduling and Flexible Flow Shop Problems. However, it also comprises less investigated aspects such as a specific job precedence structure resulting in a directed rooted in-tree and a global resource constraint limiting the number of simultaneously active machines. We present a straightforward adaptation of a time-indexed mathematical formulation to the problem and introduce a new lower-bounding procedure. To solve the problem, we propose constructive heuristics based on classical priority rules and adaptations of job sequencing heuristics. We also propose CORE, a specialized approach tailored to leverage the problem structure. All the algorithms are extensively evaluated on two benchmark sets, various shop floor configurations, and eight real-life scenarios. Our results reveal the general effectiveness of job sequencing approaches and demonstrate the overall superiority of CORE.

Decentralised [formula omitted] robust control of MTMDs for mitigating vibration of a slender MDOF floor configuration

In this research, a novel robust decentralised H (H∞ and H2) design combined with a pattern search method (PSM), incorporating considerations of multiple modal dynamics, was developed to address the vibration issue in slender structures. To verify the effectiveness of the concept, a full-scale laboratory reconfigurable multiple degrees of freedom (MDOF) test-bed floor panel structure was selected, equipping with a passive multiple-tuned mass damper (MTMD) as a coupling system. The optimal parameters of the MTMDs were tailored using the decentralised H design and the PSM, considering the dynamic engagement of multiple modes. Furthermore, a crucifix-type configuration of 2DOF MTMDs was proposed to mitigate the vibration of the floor panel structure. Full-scale forced vibration testing (FVT) was conducted to validate the dynamic performance of the 2DOF MTMDs. The test results provide satisfactory verification and high-quality curve-fitting testing data for parameter study and dynamic simulation. By examining the field data from the 2DOF MTMDs and performing various numerical simulations and analyses, the control performance robustness of the MTMDs was comprehensively evaluated, considering practical engineering variations such as the number and stiffness of MTMDs, as well as the stiffness and mass of the floor panel structure. As a result, the proposed H control strategies for the MTMDs demonstrated robust control capabilities by effectively dissipating significant amounts of externally applied energy.

Fundamental period equations for plan irregular moment-resisting frame buildings

The fundamental natural period of oscillation is a critical parameter in evaluating the design base shear of buildings. Worldwide seismic design codes typically employ height-based empirical formulas to estimate this period for various building categories, without distinguishing between regular and irregular buildings. This study proposes a formula specifically for reinforced concrete (RC) moment-resisting frame (MRF) buildings with dominant re-entrant corner type plan irregularity. A total of 190 re-entrant corner dominant building models with different shapes (C-, L-, T-, and PLUS-type), heights, and floor configurations were prepared, and eigenvalue analysis (EVA) was conducted. The fundamental natural period of oscillation for each model was evaluated and compared with the height-based formulas from seismic design codes and the period–height relationship proposed in existing literature. A nonlinear regression model, using a multi-variable power function, is proposed to estimate the fundamental natural period for these re-entrant corner dominant building models. This model considers the A/L ratio in both directions of the building, along with its height. Both unconstrained and constrained regression analyses were performed to derive a formula that best fits the fundamental natural period data. The study recommends that the unconstrained best-fit minus one standard deviation curve can conservatively define the fundamental natural period of oscillation for re-entrant corner dominant RC building models. The equation defining this curve has the potential to replace the existing seismic design code-based period-height formula.

Experimental flow conditions effects on a bottom-mounted ducted twin vertical axis tidal turbine compared to real sea conditions

From 2019 to 2021, HydroQuest tested its 1 MW-rated ducted twin vertical axis tidal turbine (2-VATT) at Paimpol-Bréhat test site, France. At this site, the turbulent intensity is evaluated about 15 % and extreme wave conditions up to 6 m significant wave height with 12 s peak period were observed during the two years of demonstration. In addition, the current vertical velocity profile is sheared with about 20 % velocity difference between the top and the bottom of the turbine, and the average directions of the ebb and flood tides are about 22° asymmetrical. The bottom mounted 2-VATT was instrumented for performance and loads assessment which allowed the certification of the power curve, both in flood and ebb tides, as well as the analysis of the sea state influence on the turbine behaviour. Based on that experience, the company wants to gain confidence in its design process by comparing those results to numerical and lab-scale experiments ones.
 Along the past three years, an important amount of work has been achieved to widely characterise the behaviour of the 1/20 scale 2-VATT similar to the 1MW-rated demonstrator. The turbine was tested in many different operating conditions in the Ifremer’s wave and current flume tank to try to reproduce full-scale conditions and turbine response. Those conditions include a wide range of operating points and incident velocities, facing aligned and misaligned currents, with and without vertical velocity shear, with and without bathymetry generated turbulence, with and without surface waves following and against the current. In this presentation, we propose to synthesise the effects of all these conditions on the 2-VATT response to highlight the most critical ones in the design process of such a device, in comparison to the results obtained at sea.
 To this date, we showed that the lab-scale model behaviour differs between ebb and flood tide current conditions due to the difference of relative counter-rotation of the two columns of rotors and to the base asymmetry. The wake is also significantly different as it recovers 30 % faster in the flood tide configuration compared to the ebb. We also found that the presence of a sheared and misaligned incident current barely affects the ducted 2-VATT average performance. However, it modifies the torque repartition between the rotors leading to an increase of the power fluctuations. Furthermore, when adding bathymetry obstacle upstream, the high flow shear and turbulence also generate strong power fluctuations on the 2-VATT. The load fluctuations are significantly increased, impacting the structure fatigue compared to a flat floor configuration, but the risks of device drifting or toppling are not affected. The waves impact the power and loads fluctuations too while barely affecting the average performance; and the average performance increases with the Reynolds number in the tank. Those two latter points still need investigations to better characterise their effect on the 2-VATT.

The cosmic radio dipole: Bayesian estimators on new and old radio surveys

The cosmic radio dipole is an anisotropy in the number counts of radio sources and is analogous to the dipole seen in the cosmic microwave background (CMB). Measurements of source counts of large radio surveys have shown that, although the radio dipole is generally consistent in direction with the CMB dipole, the amplitudes are in tension. These observations present an intriguing puzzle, namely the cause of this discrepancy, with a true anisotropy breaking with the assumptions of the cosmological principle, invalidating the most common cosmological models that are built on these assumptions. We present a novel set of Bayesian estimators to determine the cosmic radio dipole and compare the results with those of commonly used methods applied to the Rapid ASKAP Continuum Survey (RACS) and the NRAO VLA Sky Survey (NVSS) radio surveys. In addition, we adapt the Bayesian estimators to take into account systematic effects known to influence large radio surveys of this kind, folding information such as the local noise floor or array configuration directly into the parameter estimation. The enhancement of these estimators allows us to greatly increase the number of sources used in the parameter estimation, yielding tighter constraints on the cosmic radio dipole estimation than previously achieved with NVSS and RACS. We extend the estimators further to work on multiple catalogues simultaneously, leading to a combined parameter estimation using both NVSS and RACS. The result is a dipole estimate that perfectly aligns with the CMB dipole in terms of direction but with an amplitude that is three times as large, and a significance of 4.8σ. This new dipole measurement is made to an unprecedented level of precision for radio sources, which is only matched by recent results using infrared quasars.

EEG alpha wave responses to sounds from neighbours in high-rise wood residential buildings

This study explored electroencephalogram (EEG) alpha waves (α-EEG) in response to neighbours’ sounds in wood residential buildings. Experiments were carried out in a laboratory to collect α-EEG data in distinct acoustics scenarios. A series of impact and airborne sounds were generated using loudspeakers and subwoofers, while the participants sat comfortably in a simulated living room wearing EEG headsets. Impact sounds were those of footsteps of adults walking on floors equipped with different timber floor configurations, whereas airborne sounds were of speech and music digitally filtered to resemble the good and poor sound insulation performances of lightweight vertical partitions. The sound sources were presented both individually and in combination (e.g. footsteps combined with music or speech). Noise sensitivity and attitudes towards neighbours were introduced as non-acoustic factors. The study highlighted significantly higher α-EEG in response to footsteps heard through floors characterised by low impact sound pressure levels (SPL) and to music heard through partition walls with low sound reduction indices. The effective duration of the autocorrelation function, τe, was computed to investigate subjective preference, and significant differences between sounds heard at various SPLs were identified for speech and music. Footsteps sounds in combination with an airborne source elicited higher α-EEG when compared to single footsteps sounds. Participants with self-reported low noise-sensitivity and positive attitude towards neighbours showed significantly larger α-EEG responses when exposed to sounds from neighbours than those who had high noise-sensitivity and negative attitude towards neighbours.

Punching tests on edge slab-column connections with refined measurements

Due to the significant shear forces developing around columns and the potential brittle failure associated, the punching capacity of flat slabs is the main concern at ultimate limit state. An effective way to understand the behaviour of slab-column connections has typically been by testing isolated specimens in the laboratory. While there exist many slab-column connection types in actual slabs, most research efforts have focused on the punching resistance at internal columns. Specifically, edge connections appear largely underrepresented in the literature when the number of existing tests is compared to their importance in typical building floor configurations. Furthermore, the favourable effect of slab continuity is generally neglected in this type of tests. This paper presents the results of an experimental campaign on two edge slab-column connections: one had no shear reinforcement, while the other had a large amount of shear reinforcement to evaluate maximum punching. A novel test setup was conceived to apply representative boundary conditions of actual continuous slabs, introducing moment continuity perpendicularly to the slab free edge. Refined measurement techniques were extensively used, monitoring the visible slab faces using Digital Image Correlation, and instrumenting the flexural and shear reinforcement with distributed fibre-optic sensors. The failure of the slab-column connection without shear reinforcement was triggered in the region of shear stress concentrations and propagated around the column thereafter. Well-anchored vertical legs of flexural reinforcement at the free face induced a smeared-like shear crack pattern. In the shear-reinforced slab-column connection, an initial crushing of the concrete at the column front corners was followed by the formation of a local yield line along the slab axis. In addition to the enhancement of the resistance and rotation capacity, the shear studs also served for increasing the moment redistribution capacity of the system. The experimental results are compared to different codes of practice, showing that improvements are needed to better assess the resistance of edge columns.

Effect of neighbours sounds in wooden residential buildings on restorative EEG rhythm (Alpha waves)

The present study aimed to explore the effect of neighbours sounds commonly heard in wooden residential buildings on restorative EEG rhythm represented by Alpha waves. Thirty participants took part in a listening test which was performed to collect EEG data in distinct acoustics scenarios. Noise sensitivity and attitude toward neighbours were introduced as non-acoustic moderators and assessed through questionnaires before the experiment. A series of impact and airborne sounds were presented through loudspeakers and subwoofer, while participants sat comfortably in the simulated living room wearing the EEG headset (B-alert X24(r) system). The impact sound sources were two types of footsteps, adult walking and child running, recorded in a laboratory on different floor configurations and thus, varying in sound pressure level and frequency characteristics. The airborne sound sources were a lively conversation and a piece of classical piano music, digitally filtered to represent good and poor sound insulation performances of vertical partitions. The effect of sound stimuli and non-acoustic factors on restorative EEG rhythm corresponding to Alpha waves (8-13 Hz) was then analysed. Differences in response to distinct acoustic scenario were observed. Additionally, Alpha band activity showed to be affected by noise sensitivity and attitude toward neighbours of participants.

Modeling and Simulation of In-Hospital Disaster Medicine in a Mass Casualty Event for the Resilience Evaluation of BCPs

In this study, we developed a simulation model of detailed in-hospital disaster response to a mass casualty incident based on the analysis of related documents and actual in-hospital disaster response training, aiming to assess the hospital’s response capacity under various disaster situations. This simulation model includes detailed models of patients, floor configurations, resources, and response tasks, which consider resource requirements for the treatment of different patients with various injuries and physical conditions. The model covers patients’ arrivals to hospitalization or discharge. We conducted simulations of the target hospital to test two resource allocation strategies under two patient scenarios. By comparing the results under different resource allocation strategies, we found that the X-ray photography examination capacity could become a fundamental bottleneck in responding to mass casualty incidents. Also, we found that the appropriate resource allocations and quick replenishment could alleviate the negative effect of resource shortages and maintain a higher performance. Furthermore, the results show that the length of stay can be heavily affected by the patients’ configuration. As a result, by monitoring and anticipating the situation, a resilient and responsive resource allocation strategy must be prepared to handle such uncertain disaster situations.

Gap volume and sealer penetration of C-shaped root canals obturated with cold hydraulic technique and calcium silicate sealer.

This study compared the gap volume and sealer penetration in C-shaped root canals prepared with adaptive core rotary files and obturated with cold hydraulic compaction using calcium-silicate sealer, warm vertical hybrid compaction, or lateral compaction using epoxy-resin sealer. Thirty-six extracted mandibular molars with pulpal floor configuration Types I and III were used. The teeth were prepared using XP-Shaper and XP-Finisher and obturated with: group 1: cold hydraulic compaction/calcium silicate, group 2: warm vertical hybrid compaction/epoxy resin, or group 3: lateral compaction/epoxy resin. The gap volume was evaluated using μ-CT. The sealer penetration depth and area were evaluated using confocal laser scanning microscopy. The gap volume in groups 1, 2, and 3 was 0.82%, 0.24%, 0.80%, respectively, which were not significantly different (p> 0.05). The gap volumes in the obturated C-shaped canals were not significantly different among the CHC/CSBS, WHC/ERS, or LC/ERS groups. CHC/CSBS was the most convenient technique.

Shaking Table Tests of a Novel Flat Slab-Flanged Wall (FSFW) Coupled System with Embedded Concrete-Filled-Steel-Tubes in Wall Piers

The flat slab-flanged wall (FSFW) coupled system has gained popularity in recent years; however, its seismic performance remains an issue, as beams and columns in it are commonly eliminated. To tackle this problem, embedding concrete-filled steel tubes (CFSTs) in wall piers has been proposed to strengthen the system; the viability of this approach has been verified at the member level. Along this line, this study embarks on a shaking table testing of a 1/8-scale five-story FSFW structure equipped with CFSTs in walls, with an aim to understand the overall seismic behavior of such an enhanced system. As with the practice in many countries, the plan layout of the test structure consisted of four rows of wall piers, thus presenting a ‘fish-bone’ floor configuration that relied only upon the walls to resist gravity and lateral loads. The structure was subjected to a suite of input ground motions along with white-noise excitations. By so doing, its damage progression, pattern and dynamic characteristics were clearly identified. Furthermore, a non-linear time history analysis was conducted using PERFORM-3D, and the goodness-of-fit of the computed responses to the experimental records was examined. Findings indicated that the application of CFSTs was instrumental in resisting the simulated earthquake loads acting on the FSFW system, hence the global response limits required by codes of practice were met, even in the case of extremely strong earthquakes. Nevertheless, the junction between the shear walls and floor slabs was found to be the weakest links in the whole system. Designers are thus cautioned to implement proper detailing in those regions to prevent local distress, though it did not appear to acutely impair the system’s collapse-resisting capacity.

Correlation tests on train aerodynamics between multiple wind tunnels

Wind tunnel tests on rail vehicles, especially the crosswind evaluation, are often used for the determination of critical wind characteristics. To increase the reliability of the wind tunnels for these requirements, correlation data between various wind tunnels is necessary. Along those lines, a wind tunnel campaign on a 1/20th high-speed train was conducted at three separated facilities, including the study of two floor configurations within the same wind tunnel. A symmetry check was made by monitoring pressure signals at both sides of the vehicle, and the load coefficients that fall within negative and positive yaw angles. The results show good consistency with aerodynamic load coefficients measured at separated wind tunnels. The standard deviation of CMx,lee increases with the yaw angle exponentially. Pressure taps for geometric transitions and suction peaks tend to have a larger level of symmetry discrepancies than other taps. Pressure distributions for longitudinal centerline and loops in all facilities have a similar trend, while the dispersion degree slightly differs in various regions. These differences are partly explainable by the experimental settings, i.e., the boundary layer development above the floor, the offset installation of the model, and the floor configurations. Therefore, special attention is suggested to be paid to the floor configurations and boundary layers above the floor when performing related experimental works.

Evaluating Laboratory Measurements for Sound Insulation of Cross-Laminated Timber (CLT) Floors: Configurations in Lightweight Buildings

Cross-laminated timber (CLT) floors with supplementary layers or floating floors comprise a common solution in new multistory timber structures. However, bare CLT components provide poor sound insulation, especially in low frequencies during structure-borne sound propagation. Thus, floor configurations in wooden buildings deploy more layers for improved acoustic behavior. Twelve contemporary CLT floors were analyzed after laboratory measurements of airborne sound reduction and impact sound transmission utilizing the following indicators: Rw, Rw, 100, Rw, 50, Ln,w, Ln,w,100, and Ln,w,50 (per ISO 10140, ISO 717). An increase in sound insulation was achieved thanks to added total mass and thickness, testing layers of the following: elastic mat for vibration isolation, wool insulation, gypsum boards, plywood, concrete screed, and wooden parquet floor. The results indicate that multilayered CLT floors can provide improvements of up to 22 dB for airborne sound and 32 dB for impact sound indicators compared with the bare CLT slab. Floating floor configurations with dry floor solutions (concrete screed) and wooden parquet floors stand out as the optimal cases. The parquet floor provides a 1–2 dB improvement only for impact sound indicators in floating floor setups (or higher in three cases).

Optimization of the configuration and flexible operation of the pipe-embedded floor heating with low-temperature district heating

The radiant heating is cost effective way of space heating while providing favourable thermal comfort. Due to the large thermal flexibility, it is possible to utilize the pipe embedded radiant heating for low-temperature heating and demand management, thereby giving more access to the low-grade heat sources such as the renewable energy or the industrial waste heat. In this study, we investigate the optimal configuration of the radiant floor heating system considering different district heating (DH) scenarios. We propose the scheduled control strategy considering the comfort requirements, the occupancy and the dynamic energy price. Parametric simulations regarding the pipe spacing, the thickness of the concrete core, and the DH supply temperatures are performed by Modelica models. The critical levels of the radiant floor configurations of applying medium-temperature DH (MTDH), low-temperature DH (LTDH) and ultra-low temperature DH (ULTDH) are investigated. The indoor comfort, the thermal performances, the economy performances and the energy flexibility as the crucial factors of different cases are analysed and compared. The results show that the pipe spacing of 300 mm achieves better comfort and shorter charging time for all DH scenarios of the case nearly zero energy building (NZEB). The larger thickness of the concrete core can stabilize the indoor temperature variation and buffer the impact from the environmental disturbance more effectively.

Morphometric analysis of three-rooted mandibular first molars in a Slovene population: a macroscopic and cone-beam computed tomography analysis.

This study examined the root morphology of mandibular first molars (MFMs) with radix entomolaris (RE), which presents diagnostic and therapeutic challenges for clinicians. A total of 17 three-rooted MFMs were taken from a collection of extracted teeth. Root lengths and levels of furcations were measured with a digital calliper. The pulp floor configuration, root canal systems, and RE canal curvatures were evaluated using the cone-beam computed tomography scans. Radix entomolaris was either located disto-lingually, with its coronal portion fixed to the distal root (n = 16) or mid-lingually (n = 1). A literature search identified four additional cases of MFMs with RE located mid-lingually. In the present study, RE was significantly (p ≤ 0.001) shorter than the distal root (DR) and the mesial root, on average by 2.04 mm and 3.15 mm, respectively. The level of the distal furcation was significantly (p = 0.003) lower than that of the mesiodistal furcation, on average by 1.39 mm. The average divergence angle formed by the cervical portions of the RE and DR canals was 53.14°. All RE canals were severely curved (> 25°) in buccolingual direction. The RE orifice was located slightly disto-lingually to considerably mesio-lingually from the DR orifice. The traditional assumption of a disto-lingually located RE needs to be changed, even though this is the most prevalently found variant of this anatomy. The additional variant includes the presence of a mid-lingually located RE, which has implications for the endodontic access cavity design.

Cross-platform classification of level and deformed sea ice considering per-class incident angle dependency of backscatter intensity

Abstract. Wide-swath C-band synthetic aperture radar (SAR) has been used for sea ice classification and estimates of sea ice drift and deformation since it first became widely available in the 1990s. Here, we examine the potential to distinguish surface features created by sea ice deformation using ice type classification of SAR data. Also, we investigate the cross-platform transferability between training sets derived from Sentinel-1 Extra Wide (S1 EW) and RADARSAT-2 (RS2) ScanSAR Wide A (SCWA) and fine quad-polarimetric (FQ) data, as the same radiometrically calibrated backscatter coefficients are expected from the two C-band sensors. We use a novel sea ice classification method developed based on Arctic-wide S1 EW training, which considers per-ice-type incident angle (IA) dependency of backscatter intensity. This study focuses on the region near Fram Strait north of Svalbard to utilize expert knowledge of ice conditions during the Norwegian young sea ICE (N-ICE2015) expedition. Manually drawn polygons of different ice types for S1 EW, RS2 SCWA and RS2 FQ data are used to retrain the classifier. Different training sets yield similar classification results and IA slopes, with the exception of leads with calm open water, nilas or newly formed ice (the “leads” class). This is caused by different noise floor configurations of S1 and RS2 data, which interact differently with leads, necessitating dataset-specific retraining for this class. SAR scenes are then classified based on the classifier retrained for each dataset, with the classification scheme altered to separate level from deformed ice to enable direct comparison with independently derived sea ice deformation maps. The comparisons show that the classification of C-band SAR can be used to distinguish areas of ice divergence occupied by leads, young ice and level first-year ice (LFYI). However, it has limited capacity in delineating areas of ice deformation due to ambiguities between ice types with higher backscatter intensities. This study provides reference to future studies seeking cross-platform application of training sets so they are fully utilized, and we expect further development of the classifier and the inclusion of other SAR datasets to enable image-classification-based ice deformation detection using only satellite SAR.

Effects of a Labyrinth Weir with Outlet Ramps on Downstream Steep-Stepped Chute Sidewall Height Requirements

Labyrinth weirs are commonly used to increase spillway discharge capacity. Stepped chutes represent a common spillway element used to help dissipate kinetic energy, thus reducing the size requirement and often the cost of the downstream energy dissipation basin. When combined, the complex, highly turbulent, aerated flow patterns generated by the labyrinth weir create different aeration inception point behaviors relative to traditional stepped chute applications (e.g., linear weir upstream). To reduce the risk of erosion and other damage near the spillway, stepped chute sidewalls are typically designed with sufficient height to contain the majority, if not all, of the bulked air-water spillway flow and surface waves. This study evaluated some of the hydraulic impacts of coupling a labyrinth weir with a relatively steep-stepped chute (08H:1V) at the laboratory scale in an effort to provide some useful guidance related to the sizing stepped chute wall heights. Test results showed that required chute wall heights for bulked flow containments were higher at the chute entrance than the traditional stepped chute (i.e., no labyrinth weir) design predictions. Placing ramped floors in the labyrinth weir downstream cycles facilitates the transition from the labyrinth outlet cycles to the steep chute and, in some cases, reduced maximum chute water levels. To better understand this phenomenon and provide guidance toward the use of ramped floors to reduce chute wall height requirements, the hydraulic behavior of various ramped floor configurations was systematically evaluated. The results for the geometries tested ranged from no effect to a 15% reduction in maximum chute flow depth.

Electroencephalogram (EEG) responses to indoor sound sources in wooden residential buildings

The present study aimed to explore relationships between physiological and subjective responses to indoor sounds. Specifically, The electroencephalograms (EEG) responses to neighbour sounds in wooden dwellings were investigated. Listening tests were performed to collect EEG data in distinct acoustics scenarios. Experimental work was carried out in a laboratory with a low background noise level. A series of impact and airborne sounds were presented through loudspeakers and subwoofer, while participants sat comfortably in the simulated living room wearing the EEG headset (B-alert X24 system). The impact sound sources were an adult walking and a child running recorded in a laboratory equipped with different floor configurations. Two airborne sounds (a live conversation and a piece of classical piano music) were digitally filtered to resemble good and poor sound insulation performances of vertical partitions. The experiment consisted of two sessions, namely, the evaluation of individual sounds and the evaluation of the combined noise sources. In the second session, pairs of an impact and an airborne sound were presented. During the listening test, electroencephalography alpha reactivity (α-EEG) and electroencephalography beta reactivity (β-EEG) were monitored. In addition, participants were asked to rate noise annoyance using an 11-point scale.

A Sound Insulation Prediction Model for Floor Structures in Wooden Buildings Using Neural Networks Approach

Recently, machine learning and its applications have gained a large attraction in different fields. Accurate predictions in building acoustics is vital especially in the design stage. This paper presents a sound insulation prediction model based on Artificial Neural Networks (ANNs) to estimate acoustic performance for airborne and impact sound insulation of floor structures. At an initial stage, the prediction model was developed and tested for a small amount of data, specifically 67 measurement curves in one third octave bands. The results indicate that the model can predict the weighted airborne sound insulation for various floors with an error around 1 dB, while the accuracy decreases for the impact sound especially for complex floor configurations due to large error deviations in high frequency bands between the real and estimated values. The model also shows a very good accuracy in predicting the airborne and impact sound insulation curves in the low frequencies, which are of higher interest usually in building acoustics. Keywords: building acoustics, airborne sound, impact sound, prediction model, neural networks

Computational modeling of heterogenous pore structure and airflow distribution in grain aeration system

To understand the significance of heterogeneous pore structure characteristics and its overall effect on airflow distribution and pressure drop within stored bulk grains, porosity and tortuosity models developed based on grain compaction were incorporated into the computational fluid dynamics (CFD) model using ANYSS FLUENT. CFD Fluent simulations were developed for both constant (homogenous) and variable (heterogenous) pore structure beds and validated. Generally, comparing experimentally measured data with the predicted values obtained from the simulations indicated that the simulated static pressure drop for compaction was about 31.9% higher than that for non-compaction at airflow velocity of 0.1 m s−1. The relative standard error in pressure drop between the experimental data and simulated values for compaction was below 9.5% whereas the standard error between the experimental data and the simulated values without considering compaction was more than 51.8%. This indicated that the CFD model including the compaction effect were in close agreement with the reported experimental data when compare with the results from the CFD model without considering compaction effect. Thus, the developed variable pore structure (heterogenous) CFD model was applied in different scenario to predict airflow velocities and pressure drop distributions in aeration systems for various floor configurations, aspect ratios, and horizontal airflow designs.