Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A “plastic flow plateau” area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.

This paper studies the effect of sample size on the stress-strain behavior and strength characteristics of geotextile reinforced sand using the finite element numerical analysis. The effect of sample size was investigated by studying the effects of varying the number of geotextile layers, the confining pressure and the type of geotextile. Modeling was performed on samples with five different diameters: 38, 100, 200, 500 and 600 mm. The elastic-plastic Mohr-Coulomb model was used to simulate sand behavior. Results showed that small-sized samples show higher values of peak strength and higher axial strain at failure in comparison with large-sized samples. The size effect on the behavior of samples became further apparent when the number of geotextile layers was increased or the confining pressure was decreased. In addition, the results indicated that the magnitude of the size effect on the mechanical behavior of reinforced sand decreases with an increase in the sample size.

This paper deals with the internal force and the deformation matrixes, both of which can be used to analyze the topological relationship of a structure. Based on the reciprocal theorem, the relationship between the two matrixes is established, which greatly simplifies the computation of the internal force matrix. According to the characteristics of the internal force matrix, the transfer law of the matrix itself (due to the removal of components) is established based on the principle of linear superposition. With the relation of the two matrixes, the transfer law of the deformation matrix is also obtained. The transfer law illuminates the change regularity of internal force or deformation of the remnant structure when certain members are cut off one after another. The results of numerical examples show that the proposed methods are correct, reliable and effective.

A two-stage method is developed to solve a new class of multi-storage tank multi-source (MTMS) systems. In the first stage, the optimal storage policy of each tank is determined according to the electricity tariff, and the ground-level storage tank is modeled as a node. In the second stage, the genetic algorithm, combined with a repairing scheme, is applied to solve the pump scheduling problem. The objective of the pump scheduling problem is to ensure that the required volume is adequately provided by the pumps while minimizing the operation cost (energy cost and treatment cost). The decision variables are the settings of the pumps and speed ratio of variable-speed pumps at time steps of the total operational time horizon. A mixed coding methodology is developed according to the characteristics of the decision variables. Daily operation cost savings of approximately 11% are obtained by application of the proposed method to a pressure zone of S. Y. water distribution system (WDS), China.

N₂ and N₃ are known as the transition points of the three principal stages of fatigue: initial accommodation, accretion of damage and terminal fatigue. Many experiments show that the ratios of N₂/N_f and N₃/N_f tend to be stable even though the specific N₂ and N₃ values may fluctuate widely. The primary goal of this research is to study the piezomagnetic field surrounding AISI 1018 steel specimen under repeated loads and to find the ratio values of N₂/N_f and N₃/N_f by analyzing 11 sets of low-cycle fatigue data. An MTS-810 testing system with a peak capacity of 222 kN was used to obtain the data which consisted of stress, strain, and piezomagnetic field. A computer program was constructed to track the evolution of the piezomagnetic field and regression analysis was carried out to determine N₂ and N₃ values. It was observed that there exists a consistent relationship between N₂ and N_f. The apparent invariance of the ratio N₂/N_f implies that N₂ may be identified as an index of performance in the early loading response of a specimen that forecasts its fatigue life, N_f. It has been demonstrated that measurements of the magnetic and mechanical hysteresis can yield significant insights into the various stages of the development of a fatigue critical microstructure which culminates in complete rupture of the material.

The objective of the present research is to investigate the relationship among tool wear, surface topography, and surface roughness when high-speed end milling Ti-6Al-4V alloy, and also to define an optimal flank wear criterion for the cutting tool to integrate tool life and the surface roughness requirements of the finish milling process. An annealed Ti-6Al-4V alloy was selected as the workpiece material, undergoing end milling with uncoated carbide inserts. The flank wear of the insert was observed and measured with the toolmaker’s microscope. To examine machined surfaces, 3D surface topography was provided by the white light interferometer, and the arithmetical mean roughness (R_a) was calculated with the WYKO Vision32 software. The flank wear increases with cutting time, and the maximal flank wear is set as the flank wear criterion. As the cutting process progresses, tool wear is the predominant factor affecting the variation of surface roughness. According to the plots for the tool wear propagation and surface roughness variation, an optimal flank wear criterion can be defined which integrates the tool life and the surface roughness requirements for the finish milling process.

The seasonal-frozen layer may have an influence on embankment motion from train-induced vibrations. Based on the field monitoring in a seasonally-frozen region of northeastern China, the effects of the frozen layer on the embankment responses to train-induced vibration were investigated in winter and summer via acceleration time histories and acceleration frequency spectrums. The results show that: (1) Compared to unfrozen soil conditions, the amplitudes of longitudinal and vertical vibrations at the points near the rail were increased, different influences of freight versus high-speed trains are the most evident. (2) With greater distance from the rail, the dominant frequency ranges of embankment with both frozen and unfrozen layers narrowed and shifted to low frequency bands. (3) The predominant frequency of embankment vibration with frozen soil layers shifted to higher frequencies with the increased train speed, although there was little change with unfrozen condition. Layer condition (frozen versus unfrozen) and distance to rail both play important roles in investigating the embankment vibration characteristics and rail transit field monitoring to improve the criterion of the rail construction in seasonally-frozen regions.

The effects of the concentration of dissolved total organic carbon (TOC), the TOC/Br⁻ ratio, bromide ion levels, the chlorine to ammonia-N ratio (Cl:N), the monochloramine dose and the chlorine dose on the formation of trihalomethanes (THMs) (including chloroform, bromodichloromethane, chlorodibromomethane, and bromoform) from chlorination were investigated using aqueous humic acid (HA) solutions. The profile of the chloramine decay was also studied under various bromide ion concentrations. Monochloramine decayed in the presence of organic material and bromide ions. The percentage of chloroform and brominated THMs varied according to the TOC/Br⁻ ratio. Total THMs (TTHMs) formation increased from 112 to 190 μg/L with the increase concentrations of bromide ions from 0.67 to 6.72 mg/L, but the chlorine-substituted THMs were replaced by bromine-substituted THMs. A strong linear correlation was obtained between the monochloramine dose and the formation of THMs for Cl:N ratios of 3:1 and 5:1. These ratios had a distinct effect on the formation of chloroform but had little impact on the formation of bromodichloromethane or chlorodibromomethane. The presence of bromide ions increased the rate of monochloramine decay.

The production of formic and acetic acids (or salts) by hydrothermal oxidation of syringol, a model compound for lignin, was investigated using a batch reactor. Results show that the highest yields of formic and acetic acids were, respectively, 59.6% and 11.3% at the reaction condition of 0.5 mol/L NaOH, 120% H₂O₂ supply and 280 掳C. These results will inform studies aiming to develop more environmental friendly lignin conversion processes by obtaining products beyond a CO₂ end product.

This study proposes a model of syngas production from municipal solid waste (MSW) gasification with air in fixed bed reactors. The model (using Aspen plus simulator) is used to predict the results of MSW gasification and to provide some process fundamentals concerning syngas production from MSW gasification. The effects of gasification temperature, air equivalence ratio and moisture concentration on the composition of syngas, lower heating value (LHV) of syngas, heat conversion efficiency, and carbon conversion are discussed. The results indicate that higher temperature improves gasification, and higher air equivalence ratio increases the carbon conversion while decreasing syngas LHV. Heat conversion efficiency increases and reaches the maximum and then decreases with the increase of air equivalence ratio. Higher moisture concentration increases the carbon conversion and increases the heat conversion efficiency at lower ratios. Higher temperature and a lower equivalence ratio are favorable for obtaining a higher LHV of syngas at the same moisture concentration.