Performance of the bearing reinforcement earth wall as a retaining structure in the Mae Moh mine,Thailand

In this research, a Bearing Reinforcement Earth (BRE) wall with a residual clay stone backfill was successfully implemented as an alternative truck ramp support for an on-site crusher plant in the Mae Moh mine, Thailand. The performance of the BRE wall during and after the end of construction as well as during the service state was evaluated in terms of, settlement, bearing stress, lateral movement, lateral earth pressure and tension force in the reinforcements. Bearing reinforcement is a cost-effective inextensible earth reinforcement, which is composed of a longitudinal member and transverse members. The maximum settlement at the end of construction (20 days) was about 5 mm. The installation of the truck ramp (10 days after the end of construction) resulted in an immediate settlement of about 2 mm. The final settlement due to the backfill, truck ramp and truck load after 270 days was found to be uniform due to the contribution of bearing reinforcement and was approximately 25 mm. The bearing stress which was uniformly distributed was found to increase rapidly with construction time, which was in agreement with the relatively uniform settlements. The lateral wall movement at the front and lateral sides at the end of construction was very small with the maximum movement (at the top of the wall) found to be less than 10 mm. As such, the ratio of lateral movement to height (δ/H) was found to be approximately 0.12%, which was lower than the allowable value of 0.4%. With this low δ/H and the insignificant change in the measured settlement and lateral movement during service, the BRE wall was considered to have a very high stability. The coefficients of lateral earth pressure, K and depth relationship were proposed based on the analysis of measured maximum tensile force in the reinforcements. The maximum tension plane of the BRE wall could be represented by the coherent gravity hypothesis. Using the proposed K and maximum tension plane, the internal stability of the BRE wall was furthermore examined. A proposed method of designing the BRE wall with claystone backfill was also proposed.     

Tunable optical and magneto-optical properties of nickel-polymer nanoparticles

Abstract

The optical and magneto-optical (MO) properties of composites containing magnetic nanoparticles were experimentally as well as theoretically found to be dependent on the interparticle spacing, surrounding medium and particle size of the constituent nanoparticles. In this work, the optical and MO properties of composites consisting of two nickel (Ni) nanoparticles (NP) and embedded in polymethyl methacrylate were theoretically investigated in the wavelength range of 400–900?nm using the discrete dipole approximation method, which accounts for optical coupling between Ni NPs. The theoretical calculations suggest that the shifts in spectral peak position depend on both interparticle distance and particle size corresponding to the experimental results. In addition, the observed optical spectra of Ni NPs showed the plasmon resonance in the visible light range in the electromagnetic wave. The basic results of this study might be used for fabricating optical and MO devices.     

Noise reduction using spatial-angular compounding for elastography

Ultrasound elastography has developed into an imaging modality suitable for detection and diagnosis of cancers in the breast, prostate, and thyroid and for monitoring ablative therapies in the liver, kidneys, and other sites. In this article, a new approach is described that enables the reduction of noise artifacts in elastography without a significant reduction in either the contrast or spatial resolution. The technique uses angular-weighted compounding of local angular strains estimated from echo signals scanned at different insonification angles. Strain estimated along angular insonification directions can be separated into strain tensor components along the axial (direction of compression) and lateral directions. The mechanical stimulus is applied only along one direction. Angular-weighting factors are derived from the relationship between the axial and lateral strains under the assumption of tissue incompressibility. Experimental results using a uniformly elastic, tissue-mimicking phantom demonstrate the improvement in the signal-to-noise ratio obtained with angular-weighted compounding. Variation in the signal-to-noise ratio obtained using different angular increments also is investigated. Elastograms obtained from an inclusion phantom also demonstrate the improvement in contrast detail resolution obtained using spatial-angular compounding.     

Correlation of RF signals during angular compounding

A theoretical analysis of the correlation between radio-frequency (RF) echo signal data acquired from the same location but at different angles is presented. The accuracy of the theoretical results is verified with computer simulations. Refinements to previous analyses of the correlation of RF signals originating from the same spatial location at different angular positions are made. We extend the analysis to study correlation of RF signals coming from different spatial locations and eventually correlation of RF signal segments that intersect at the same spatial location. The theory predicts a faster decorrelation with a change in the insonification angle for longer RF echo signal segments. As the RF signal segment becomes shorter, the decorrelation rate with angle is slower and approaches the limit corresponding to the correlation of RF signals originating from the same spatial location. Theoretical results provide a clear understanding of angular compounding techniques used to improve the signal-to-noise ratio in ultrasonic parametric imaging and in elastography.     

基于燃烧器的亚微型多分散悬浮微粒制作研究(英文)

A combustion burner for the production of submicron polydisperse aerosol particles was developed and experimentally studied in this paper. The sample particles from the generator were characterized by the scanning electron microscope ( SEM) ,the energy dispersive spectroscopy ( EDS) ,and the long electrical mobility spectrometer ( L-EMS) for morphology,chemical composition,and particle number concentration and size distribution,respectively. It was found from the SEM image that a large portion of the particles were non-spherical and were agglomerated. Polydisperse aerosols with particle number concentrations of approximately 10 14 particles /m 3 were obtained. The average diameter of the generated particles obtained by the L-EMS is in the range of approximately 5 nm to several hundred nanometers.     

Comparison of electrostatic charge and beta attenuation mass monitors for continuous airborne PM10 monitoring under field conditions

An electrostatic PM10 mass monitor (EPMM) used for wireless continuous airborne particulate matter monitoring was developed and evaluated in our previous work. However, differences in measured PM10 mass concentrations between the electrostatic charge and the beta ray attenuation methods due to the frequent occurrence of high humidity and temperature in the ambient air in Thailand’s have not been extensively studied in our previous work; and in the literature, it would be necessary to compare the output of the EPMM against the beta ray attenuation mass monitor. In this study, we evaluated the performance of the EPMM simultaneously with a commercially available FH62C14 Beta gauge continuous ambient particulate monitor, Thermo Fisher Scientific Inc., for PM10 measurements at ambient condition in the field. The measurements were made at Yupparaj Wittayalai School, Si Phum, Mueang, Chiang Mai, Thailand from November 16-23, 2015. They showed that the averages of PM10 mass concentrations measured by the EPMM linearly correlate very well with the PM10 mass concentrations measured by the FH62C14. The slopes were 0.9620 and 1.0649 for 1 and 24-hour, respectively, and R² of 0.8634 and 0.9889 for 1 and 24-hour, respectively. Finally, this comparison proved to be particularly useful in the refinement and design of the EPMM.     

Numerical simulation of 3D turbulent isothermal flow in a vortex combustor

Numerical simulations of strongly swirling turbulent flows in a vortex combustor (VC) are conducted. A comprehensive investigation of a three-dimensional isothermal VC flow using three first-order turbulence models: the standard k–ε turbulence model, Renormalized Group (RNG) k–ε model and shear stress transport (SST) k–ω model; and a second-order turbulence model, Reynolds stress model (RSM) together with a second-order numerical differencing scheme is conducted in the present work. The computation indicates that the RSM is superior to the other turbulence models in capturing the swirl flow effect in comparison with measurements. The numerical results for the VC flow provide the characteristics of the flow in terms of relevant parameters for the VC design and operation, composed of axial and tangential velocities, pressure fields, and turbulence kinetic energy.     

Durability against wetting-drying cycles for cement-stabilized reclaimed asphalt pavement blended with crushed rock

Pavement rehabilitation and reconstruction generate large quantities of reclaimed asphalt pavement (RAP). The improvement of the engineering properties of this RAP is required in order to enable it for use as environmentally friendly alternative construction material in road pavements. The durability of RAP when blended with crushed rock (CR) and stabilized with Portland cement was investigated in this paper. The CR replacement was found to improve the compactibility and durability of the stabilized RAP/CR material. For a particular RAP:CR ratio, the compaction curves of cement-stabilized RAP/CR blends were found to be essentially the same for all cement contents, but different for unstabilized blends; i.e., the maximum dry unit weight of cement-stabilized RAP/CR blends is higher than that of unstabilized RAP-CR blends. The wetting-drying (w-d) cycles led to a loss in weight of the cement-stabilized RCA/CR blends and to a subsequent reduction in strength. The w-d cycle strengths (q_u(w-d)) for a state of compaction (dry side, wet side or optimum water content) at any w-d cycle could be approximated from the corresponding initial soaked strength (prior to w-d tests) (q_u0). The q_u0 of cement-stabilized RAP/CR blends increased with an increasing CR replacement and an increasing cement content. Assuming that the CR replacement also results in an increasing cement content, w/[C(1?+?kCR_c)] was proposed as a critical parameter for developing q_u0 and q_u(w-d) predictive equations where w is the water content at the optimum water content, C is the cement content, k is the replacement efficiency, and CR_c is the CR content. Based on the q_u(w-d) predictive equation developed here, a design procedure for the laboratory mixing of cement-stabilized RAP/CR blends was proposed, which would be valuable for an accurate determination of the ingredients (RAP:CR ratio and cement content) required to attain the necessary strength at the design service life.     

An electrostatic sensor for the continuous monitoring of particulate air pollution

We developed and evaluated a particulate air pollution sensor for continuous monitoring of size resolved particle number, based on unipolar corona charging and electrostatic detection of charged aerosol particles. The sensor was evaluated experimentally using combustion aerosol with particle sizes in the range between approximately 50 nm and several microns, and particle number concentrations larger than 10¹⁰ particles/m³. Test results were very promising. It was demonstrated that the sensor can be used in detecting particle number concentrations in the range of about 2.02×10¹¹ and 1.03×10¹² particles/m³ with a response of approximately 100 ms. Good agreement was found between the developed sensor and a commercially available laser particle counter in measuring ambient PM along a roadside with heavy traffic for about 2 h. The developed sensor proved particularly useful for measuring and detecting particulate air pollution, for number concentration of particles in the range of 10⁸ to 10¹² particles/m³.     

Full scale consolidation test on ultra-soft soil improved by prefabricated vertical drains in MAE MOH mine,Thailand

The reclamation of slurry pond with ultra-soft soil deposit using the prefabricated vertical drains (PVDs) with preloading technique in the Mae Moh mine, Lampang, Thailand is a challenging work and is illustrated in this paper. Geotextile reinforcement was used to strengthen bearing capacity of the soil foundation prior to the installation of sand platform. The delay of excess pore water pressure dissipation at the early loading stage occurred despite the occurrence of large settlements was a distinct behavior of the ultra-soft soil. Within the delayed time, the calculated average degree of consolidation based on measured settlements, U_s increased while the calculated average degree of consolidation based on measured excess pore water pressures, U_e and the undrained shear strength, S_u remained unchanged. Beyond the delayed time, both U_e and S_u increased significantly with time and when U_s > 90%, the difference between U_e and U_s was observed to be small. It was suggested to use U_s for approximation of S_u when U_s > 90% based on the SHANSEP's method. The successful installation and application of PVD to improve ultra-soft soil in this research is applicable for the ground improvement of similar problematic ultra-soft soils in international land reclamation projects.