A practical application of photogrammetry to performing rib characterization measurements in an underground coal mine using a DSLR camera

Understanding coal mine rib behavior is important for inferring pillar loading conditions as well as ensuring the safety of miners who are regularly exposed to ribs. Due to the variability in the geometry of underground openings and ground behavior, point measurements often fail to capture the true movement of mine workings. Photogrammetry is a potentially fast, cheap, and precise supplemental measurement tool in comparison to extensometers, tape measures, or laser range meters, but its application in underground coal has been limited. The practical use of photogrammetry was tested at the Safety Research Coal Mine, National Institute for Occupational Safety and Health(NIOSH). A commercially available, digital single-lens reflex(DSLR) camera was used to perform the photogrammetric surveys for the experiment. Several experiments were performed using different lighting conditions, distances to subject,camera settings, and photograph overlaps, with results summarized as follows: the lighting method was found to be insignificant if the scene was appropriately illuminated. It was found that the distance to the subject has a minimal impact on result accuracy, and that camera settings have a significant impact on the photogrammetric quality of images. An increasing photograph resolution was preferable when measuring plane orientations; otherwise a high point cloud density would likely be excessive. Focal ratio(F-stop) changes affect the depth of field and image quality in situations where multiple angles are necessary to survey cleat orientations. Photograph overlap is very important to proper three-dimensional reconstruction, and at least 60% overlap between photograph pairs is ideal to avoid unnecessary post-processing. The suggestions and guidelines proposed are designed to increase the quality of photogrammetry inputs and outputs as well as minimize processing time, and serve as a starting point for an underground coal photogrammetry study.     

远场涡流技术检测带翼片管的研究

远场涡流检测对高导电管的管壁上的缺陷非常敏感，具有透壁性。探讨应用远场涡流技术检测带翼片(散热片或金属隔板组件)钢管的有关问题，分析了管外翼片对远场涡流的耦合特性和缺陷信号的影响，得出了翼片响应信号与缺陷信号的关系及缺陷信号的提取方法。     

Parametric study on design of composite–foam–resin concrete sandwich structures for precision machine tool structures

In this paper, sandwich structures for micro-EDM machines are optimized by using parametric study varying composite geometries and parameters like stacking sequence, thickness and rib geometry. The structures are composed of fibre reinforced composites for skin material and resin concrete and PVC foam (Closed cell, Divinycell) for core materials. Column structure was designed by a beam with cruciform rib and performance indices such as static bending stiffness (EI) and specific bending stiffness (EI/ρ) for dynamic stability are examined by controlling the thickness and stacking sequence of composites. For the machine tool bed, which usually has a plate shape, was designed to have high stiffness in two directions at the same time controlling stacking sequence and rib geometry; that is, rib thickness and number of ribs. The sensitivity of design parameters like rib thickness and composite skin thickness was examined and the optimal condition for high stiffness structure was suggested. Finite element analysis was also performed to verify the static and dynamic robustness of the machine structure. L-shaped joint for combining bed and column of the micro-EDM machine was proposed and fabricated using adhesive bonding. The dynamic performance such as damping characteristics was investigated by vibration tests. From the results optimal configuration and materials for high precision micro-EDM machines are proposed.     

PERIODIC DEFORMATION OF PARAMETRIC SURFACE

Deformation is a powerful tool for geometric modeling and design. Such a tool can be used to create a new shape from existing shape without restarting whole design process. A new mathematical model for producing controllable periodic deformations is proposed. By introducing cosine extension functions construct a shape operator matrix and then use the matrix to transform the position vector of some points on the object surface so as to create the deformation effects. Because the cosine extension (Unctions have a number of variable parameters with different properties, the method has corresponding interactive control means. The user can manipulate those parameters to get desirable periodic deformation effects. Experimental results show that the method is feasible and applicable to engineering and research fields such as sheet metal forming by stamping and CAD.     

Determination of single mode condition in dielectric rib waveguide with large cross section by finite element analysis

The single mode condition in large cross section rib waveguides is of great interest because almost every kind of active and passive integrated optoelectronic device or sensor is designed to sustain only the fundamental mode of propagation for better matching with optical fibers. In this paper we present a criterion to determine the single mode condition for a large cross section rib waveguides, by comparison between the numerical solutions found with Neumann boundary conditions and Dirichlet boundaries conditions applied when solving the eigenvalues problem.     

Sensitivity Analysis for a Planar SOFC: Size Effects of the Porous Gas Diffusion Layer Underneath the Channel Rib

This paper investigates the size effects of the gas diffusion layer underneath the channel rib on the performance of a planar solid oxide fuel cell (SOFC). Based on 3‐dimensional numerical simulations, the sensitivities of the electrical performance parameters (Nernst potential and current density) and the thermal performance parameters (heat generation and temperature) are examined as a function of variations in the channel rib width and anode thickness. The sensitivity values of the Nernst potential and current density are calculated to guide the design of a cell in a planar SOFC. In particular, the changes in ohmic losses for the interconnectors and anode are analyzed as a function of the variations of the channel rib width and anode thickness. The variations of the mole fractions of hydrogen, oxygen, and water in the active areas of the channel rib and the channel are presented, which provide sensitivity profiles for gas diffusion with respect to changes in the anode thickness.     

基于Revit的预制剪力墙配筋设计软件研究

预制构件配筋设计是装配式建筑深化设计过程中的关键步骤,而现有的BIM平台预制构件深化设计软件难以满足实际使用需求。本文提出了一种新的预制构件建模方法,同时在钢筋设计标准化的基础上与面向对象的软件开发方法相结合,研发了一款基于Revit软件的预制剪力墙构件配筋设计软件,并且在工程实践中获得了应用验证。     

Numerical and entropy studies of hydrogen-fuelled micro-combustors with different geometric shaped ribs

Micro-combustor design plays an important role in determining the performances of Micro Thermo-Photovoltaic (MTPV) systems. In this work, 3D numerical simulations are conducted on a hydrogen-fuelled micro-combustor with two ribs to achieve a more uniform but higher wall temperature. The effects of: 1) the shape of the ribs, 2) the axial location, 3) the height, 4) the inlet velocity and 5) the equivalence ratio are evaluated. The numerical model is built with a standard k-ε turbulence model and EDC chemical reaction model (eddy dissipation concept). These models are validated before being applied to study 3 different ribs with a cross-sectional view of: 1) rectangular, 2) Ո-shaped and 3) Ս-shaped (defined basing on the bottom rib). It is found that the combustor with 2 ribs performs generally better than that of a single-rib one under the same flow conditions. The optimum design is found to be the Ս-shaped ribs, since the mean temperature of the outer wall is increased by 25.4 K in comparison with other designs. In addition, the mean temperature is observed to increase with increased inlet velocity. However, it decreases slightly with increased rib height. Further analysis is conducted on entropy production due to chemical reactions and heat transfer processes. It is found that the chemical reaction and the conduction heat transfer contribute 70% and 15% of the total entropy generation respectively. Furthermore, the thermodynamic 2^nd-law efficiency remains in the range of 46%–51%, as the equivalence ratio varies from 0.8 to 1.2. This study provides physical insights on the optimum design of a hydrogen-fuelled micro-combustor.     

带肋钢筋尺寸超差原因及其消除

分析带肋钢筋肋间距超偏差、内径尺寸超负偏差、横肋高度尺寸超负偏差、横肋高度尺寸超正偏差、无纵肋、纵肋尺寸超正偏差、单线轧制时纵肋局部超正偏差、切分轧制时中两条纵肋大小不均、飞边等尺寸超差的原因,总结消除办法,提出持续改进措施。     

Use of serial ultrasound measures in the study of growth- and breed-related changes of ultrasonic measurements and relationship with carcass measurements in lean cattle breeds

The growth and breed-related changes of rib and rump characteristics in lean beef cattle and the ability of ultrasound to predict carcass traits were investigated. Three hundred bulls from three breeds were scanned monthly (6–7 times) using real-time ultrasound with final scans taken < 7 days prior to harvest. The rib and rump ultrasound measurements, except intramuscular fat content, increased (P < 0.05) with live weight. Breed affected most of traits. The 12th rib ultrasound measurements showed a weak to high positive correlation (0.131 to 0.976, P > 0.05 to P < 0.001) with 12th rib measurements in the carcass. Regression equations developed with the ultrasound measurements, explained 97% of the variation in longissimus muscle area, 88% of the variation in fat thickness and 57% of the variation in intramuscular fat content. When last ultrasound scan measurements were excluded from prediction equations, the R² significantly decreased. Ultrasound measures “in vivo” are viable options for assessing carcass attributes of lean cattle.