A simple constitutive model was developed to calculate the in-plane stresses of multi-ribbed composite walls subject to cyclic loadings. The equivalent strain concept was used to develop the macro in-plane model for masonry walls with the in-plane model then implemented in plane-stress finite elements. The in-plane model and a fiber model were then combined to simulate the stresses in multi-ribbed composite walls. The results show that the model accurately simulates the stresses in a multi-ribbed composite wall under plane stresses. The accurate results fully reflect the macroscopic phenomena in the masonry components and the stress distribution cloud diagram in the masonry structure is more intuitive. These results verify the accuracy and applicability of the model.

This paper describes a numerical simulation of the dust movement during dry drilling in a coal seam to reduce dust pollution and improve dust control in a mine. SolidWorks and DesignModeler are used to build the models with Fluent then used to calculate the flow field. The results show that the jet flow from the cyclic slits and the continuous rotation of the drill pipe spew dust particles out from the bottom hole at high speed in the direction of the orifices. As the dust particles move away from the drill, the dust diffusion and mass flow rate gradually decrease. The R-R distribution index increases slowly with the median dust particle diameter and the R-R characteristic size first increasing and then decreasing. The dust concentration gradually increases to a maximum and then fluctuates a small amount around the maximum over time. The dust mass concentration along the seam quickly rose to a maximum, then dropped sharply and then more slowly. The results are then used to determine the structural parameters of dust control equipment during dry drilling in coal seams.

Moderately thick plates have defects such as indentations, roll marks and scratches from the production processes. Since serious defects can negatively impact the next rolling process, operators must identify serious defects containing iron oxide defects on the surface to improve the quality of iron and steel products. A scale invariant feature transform (SIFT) operator was used to extract feature vectors that are scale rotation invariant. A Euclidean distance similarity measure is used for image matching to identify the surface defects of moderately thick plates. Many tests were then run to identify the proper values of each parameter. The SIFT algorithm then had a 95% surface defect recognition rate and was especially effective for continuous defects. Thus, this SIFT method which is unaffected by the illumination and is rotation and affine invariant gives excellent recognition of iron oxide defects.

Face-gear drives have great potential in the aviation and automotive industries. However, torsional vibrations are a key issue in face-gear pairs. This study focuses on modeling and analyses of the torsional vibrations in a face-gear pair. A torsional vibration model is given for a one-input, one-output face-gear drive with asymmetric time-varying mesh stiffness, backlash nonlinearity and static transmission errors. The torsional mesh stiffness of a face-gear pair is calculated from a loaded tooth contact analysis in a numerical example. The torsional vibration model is validated by comparing the responses with the dynamic responses predicted by Abaqus. The model is then used to analyze the dynamic behavior of a face-gear pair for the design conditions to investigate the effects of mesh stiffness, backlash, static transmission errors, and torque fluctuations on the dynamic characteristics of the face-gear pair and the nonlinear dynamic response. The results show that the model accurately predicts the face-gear pair torsional vibrations and can be used to study the mesh characteristics and the dynamic characteristics of face-gear pairs to guide the design of face-gear pairs.

An parametric analytical model was developed for the continuous rotating detonation turbine engine (CRDTE) to predict the engine performance for various compression ratios and turbine inlet temperatures. The results show that increasing the compression ratio first increases the specific thrust and the thermal efficiency but they then decrease. Increasing the turbine inlet temperature increases the specific thrust and the thermal efficiency. The engine has better overall performance than a conventional aero-turbine engine with the same cycle parameters over the entire working range as explained by the results. The specific thrust is significantly better than that of the advanced F119 aero-turbine engine and the specific fuel consumption is reduced slightly for the same cycle parameters. Thus, the CRDTE design is quite reasonable and this model can be used for engineering designs.

Urban roads are very important for draining excessive rainfall. A routing-enhanced detailed urban stormwater model (REDUS) is developed, and two main roads in the Tsinghua University campus are selected to evaluate how well the road system enhances drainage during typical storms and to quantify the impacts of rainfall type, road longitudinal slope and underground pipe systems. The results show that for the Beijing "721" stormwater event, the roads can drain as much as 50% of the total flooding discharge and the drainage increases dramatically when the pipe network reaches its maximun drainage capacity. The road drainage effectiveness is sensitive to the rainfall characteristics with the drainage correlating well with the maximum 30-min rainfall volume. Branch pipe networks do not continually increase the road drainage effectiveness as the road longitudinal slope increases which indicates that the road flows are closely connected to the flows in the underground pipes. The results will facilitate construction of Sponge City that effectively incorporates the road drainage.

The traditional depth-averaged 2-D hydrodynamic models for bend flow simulations assume velocity profiles for the secondary flow terms in the momentum equations which are unable to adjust to dynamic conditions. More flexible three-dimensional models are not very efficient. A simplified 3-D model using a spectral method in the vertical direction was developed with the flow velocity components modeled by orthogonal polynomials in the vertical direction using polynomial coefficient equations obtained using the weighted residuals method with the advection terms defined at the vertical Gauss points by the semi-Lagrangian scheme. Simulated flow structures in a sharp bend open channel match well with measured data for polynomials having degrees larger than 1 with reasonable flow structures. The mean error of the predicted main flow location is less than 7%, equivalent to other 3-D hydrodynamic models. The eddy viscosity is solved in a simple way with consideration of the turbulence anisotropy between the vertical and horizontal directions. Since this method does not have a vertical grid, the calculational efficiency is proved to be to 2-D models.

The loading paths used for sheet metal forming affect its elastic-plastic flow behavior. Quenching & partitioning (Q&P) 980 steel was used here as the research object. Two-step tensile tests using different angles relative to the rolling direction were conducted at room temperature to obtain the stress-strain curves for various stress states. The equal volume plasticity work principle was used to determine the experimental yield loci of different equivalent plastic strain (0%, 1%, 4%, 6%). The results show that the initial flow stress is significantly reduced by changing the strain path, especially in the 45° and 90° directions, the flow stress after the transient period various by a fixed amount, and the anisotropy is quite large for larger strains. The test yield loci line is convex and some of the yield loci are asymmetric. As the deformation increases, the yield loci expand outward. Simple loading and cyclic loading were compared to analyze the elasto-plastic behavior and develop unloading string mathematical models. The elastic modulus decreases quickly with increasing strain, then decreases slowly and then becomes constant. For a given plastic strain, the change in the elastic modulus during cyclic loading is greater than when simply loaded.

Positron emission tomography (PET) usually uses scintillation detectors consisting of crystal arrays and photoelectric sensor arrays. In recent years, silicon photomultipliers (SiPMs) have been more widely used in PET detectors. Although a closely arranged SiPM array can give high performance, a sparse array gives a more cost-effective system. This paper describes a sparse 8×8 SiPM array using the MicroFB-30035-SMT chip from SensL Inc. The array size is 33.7 mm×33.7 mm while the SiPM chip is 3.16 mm×3.16 mm; thus, the gap ratio is 44%. The sparse SiPM array and a dual-layer offset LYSO array were used in a high performance depth PET detector. The gaps between the SiPMs are dead zones which reduce the optical photon collection. Thus, this work studies the effects of adding enhanced spectral reflector films into the gaps. Flood maps were acquired with and without reflectors at room temperature with the crystal response analyzed to find the photopeaks, energy resolution and root-mean square (RMS) of the crystal response. The results show that the reflectors in the gaps effectively enhance the photon collection (25.5% increase) and optimize the energy resolution of the detector (from 13.48% to 12.80%). The quality of the flood map is also improved, i.e. the intrinsic spatial resolution of the PET detector.

Liquid sloshing is a common phenomenon that can cause instabilities in aircraft, can damage the tanks, and can complicate liquid level monitoring. Therefore, sloshing suppression has been extensively studied. The most common method is to arrange baffles in the tanks. The porous media model based on Darcy's law provides a simple method for simulating flows in tanks with porous baffles. In this study, experimental data was used to verify the reliability of numerical simulations used to investigate the influence of various immersion depths of horizontal porous baffles on liquid sloshing for low-frequency, large-amplitude sloshing conditions. The results show that the sloshing crests and troughs change more with higher sloshing crests because of the baffles in some cases. The baffles disturb the liquid surface which make the liquid surface oscillate more than without baffles. Thus, the baffles increasing the liquid sloshing in some cases.

A geographic information system (GIS) and exploratory spatial data analysis were used to explore the complex spatial morphology of the urban benchmark land price digital elevation model (DEM) for residential use with Wuhan, China as a case study. The multi-dimensional spatial visualization gives a better understanding of the spatial characteristics of urban benchmark land prices with the results used to validate the urban spatial structure assumptions. The results indicate that the inverse distance weighted (IDW) method is more suitable for estimating the "terrace" spatial form of the benchmark land price. The "distance to the center", a classical space variable, is the best for depicting the urban spatial structure, each side view of the spatial form and its "price skyline", the land price distribution along the ring roads from inside to outside the city and the gradient of the price curves in all directions. All these reflect the "center to edge" distribution with all the prices gradually declining away from the center with significant spatial heterogeneity between city sectors. The slopes, aspect ratios and terrain curvatures further confirm the spatial features of "terrace" and "ring road radiation" of the urban benchmark land price DEM in Wuhan.