Surface and topography metrology in firearm evidence identification and engineering surface quality control

This thesis is a topical review on the application of Surface and Topography Metrology in Firearm Evidence Identification and Engineering Surface Quality Control. It summarizes my research work at the National Institute of Standards and Technology (NIST) from 1987 to present, where I’m a Project Lead for the Forensic Topography and Surface Metrology since 1997. I started my research in surface metrology since 1982 -- after my MS study at the Harbin Institute of Technology (HIT, Harbin, China) from 1978 to 1981. In 1985, I designed, manufactured and patented the Precision Random Profile Roughness Specimens in Beijing aimed to provide a reference standard for quality control of smooth engineering surfaces [1]. These specimens were manufactured with Ra values ranging from 0.015 μm to 0.1 μm -- less than 1/10 of the similar specimens developed by PTB (Physikalisch-Technische Bundesanstalt) in Germany. These specimens were successfully used by U.S. manufacturers for measurement unification and quality control of smooth engineering surfaces, and were included in ASME B46 surface standard in 1995. Microform metrology is a subfield of surface metrology that involves surface measurements of complex geometry features on the micrometer scale. In 1995, I led a team at NIST which established a Microform Calibration System with the lowest calibration uncertainty in the world for calibration of Rockwell hardness (HR) diamond indenters. Based on the precision calibration of HR indenters and the control of other influencing quantities, I proposed a “Metrological Approach” to unifying international HRC scales with metrological traceability. I led an international HRC comparison among five National Metrological Institutes (NMIs). The comparison results strongly supported the proposed Metrological Approach. I drafted a joint paper for five NMIs entitled “Establishing a worldwide unified Rockwell hardness scale with metrological traceability” which was published at the Metrologia 34, 1997 in Paris [4]. Surface and topography metrology provides strong support to firearm evidence identifications. Based on my experience in developing surface standards, measurement systems, uncertainty and traceability procedures, I led a research team which developed the NIST Standard II Reference Material (SRM) Bullets and Cartridge Cases, and the NIST 2D/3D Topography Measurement System [5]. We formulated a National Traceability and Quality System using the SRM Bullets and Cartridge Cases to support ballistics identifications within the National Integrated Ballistics Information Network (NIBIN) in the United States [6]. I have recently invented a Congruent Match Cells (CMC) method for accurate ballistics identification and error rate estimation [7], which can serve as a statistical foundation for estimating error rates in firearm evidence identifications, thus emulating methods used for forensic identification of DNA evidences [8]

A review of NIST projects in surface and topography metrology for firearm evidence identification in forensic science

This is a review of the National Institute of Standards and Technology’s (NIST) efforts in surface metrology and topography measurements for firearm evidence identifications in forensic science. Based on the research projects in surface metrology and standardization, NIST researchers have developed Standard Reference Material (SRM) Bullets and Cartridge Cases (Certain commercial equipment, instruments, or materials are identified in this paper to specify adequately the experimental procedure. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose) and established a 2D/3D Ballistics Topography Measurement System. They formulated a Traceability and Quality System to support nationwide ballistics identifications within the National Integrated Ballistics Information Network (NIBIN) in the United States. They have recently proposed a Congruent Matching Cells (CMC) method for accurate ballistic identification and error rate estimation, which provides a statistical foundation and a practical method to promote firearm evidence identifications from qualitative image comparisons to quantitative topography measurements

Residual Stress Nondestructive Testing Technology Using Nonlinear Ultrasonic

The nonlinear ultrasonic theory is that ultrasonic waves interact with micro defects and the higher harmonic waves appear when the ultrasonic waves propagate in materials. The acoustic nonlinear parameters are sensitive to micro defects in the nonlinear materials. They are used to characterize the nonlinear characteristics of materials. The nonlinear ultrasonic theories and the characterization of stress in metal by the nonlinear ultrasonic are studied. The nonlinear ultrasonic testing system is built to detect the received signals which propagate in materials with stress. The variation trends of the nonlinear parameters is studied in tensile testing. This paper studies the relationship between nonlinear parameter and stress in different coupling states including contact coupling, air coupling, water coupling. Use manipulator to measure residual stress based on nonlinear ultrasonic and achieve a rapid, non-contact and non-destructive testing

A new integrable two-component system with cubic nonlinearity

In this paper, a new integrable two-component system, mt=[m(uxvx−uv+uvx−uxv)]x,nt=[n(uxvx−uv+uvx−uxv)]x, where m=u−uxx and n=v−vxx, is proposed. Our system is a generalized version of the integrable system mt=[m(u2x−u2)]x, which was shown having cusped solution (cuspon) and W/M-shape soliton solutions by Qiao [J. Math. Phys. 47, 112701 (2006). The new system is proven integrable not only in the sense of Lax-pair but also in the sense of geometry, namely, it describes pseudospherical surfaces. Accordingly, infinitely many conservation laws are derived through recursion relations. Furthermore, exact solutions such as cuspons and W/M-shape solitons are also obtained

A stability analysis of turning process considering the workpiece as a Timoshenko beam

In past studies, the elastic effects of a workpiece were usually ignored or a workpiece was just expressed with Euler-Bernoulli beam theory in turning process, which made the stability of cutting process less accurate. This paper considers the deformation of the workpiece expressed with a more accurate Timoshenko beam model in analysis for chatter of cutting process. The cutting stability of the turning process is analyzed by combining both the elastic effects of the tool and the workpiece with regenerative chatter mechanisms and compared with the stability analysis results that the deflection of workpiece is ignored. Besides, the influences of workpiece length, radius, the cutting tool damping and stiffness on the analytical model are also studied. At last, the present model is compared with those obtained from Euler-Bernoulli theory. It is found that the critical chip width when we consider workpiece as a Timoshenko beam is greater than the other two cases

Hysteretic behavior simulation of novel rhombic mild steel dampers

Structural vibration control technique is an appropriate and acceptable method to control structural vibration condition and dissipate structural vibration energy during severe earthquakes and violent winds. Metallic dampers are verified to be stable and effective for passive control by many scholars and engineers. Low-yield-point (LYP) steel provides a promising prospect for energy dissipation dampers widely applied in structural engineering practice. Experimental study was conducted on a novel rhombic steel plate damper in former research and numerical simulation of the hysteretic behavior of rhombic dampers was performed in this study. Mechanical performance and implementation of the novel rhombic steel plate damper is briefly introduced in this paper. The hysteretic behavior of the novel rhombic steel plate dampers made of three types of steel was investigated by testing and finite element method. It is concluded that the yield strength enhancement of the rhombic steel damper made of LYP steel is substantial. The numerical simulation results of the hysteretic behavior of the rhombic steel plate damper are similar to the experimental results for these three types of steel. The energy dissipation capability of rhombic LYP steel dampers is excellent and adequate to be used in passive control strategy for civil engineering structures

InstMove: Instance Motion for Object-centric Video Segmentation

Despite significant efforts, cutting-edge video segmentation methods still remain sensitive to occlusion and rapid movement, due to their reliance on the appearance of objects in the form of object embeddings, which are vulnerable to these disturbances. A common solution is to use optical flow to provide motion information, but essentially it only considers pixel-level motion, which still relies on appearance similarity and hence is often inaccurate under occlusion and fast movement. In this work, we study the instance-level motion and present InstMove, which stands for Instance Motion for Object-centric Video Segmentation. In comparison to pixel-wise motion, InstMove mainly relies on instance-level motion information that is free from image feature embeddings, and features physical interpretations, making it more accurate and robust toward occlusion and fast-moving objects. To better fit in with the video segmentation tasks, InstMove uses instance masks to model the physical presence of an object and learns the dynamic model through a memory network to predict its position and shape in the next frame. With only a few lines of code, InstMove can be integrated into current SOTA methods for three different video segmentation tasks and boost their performance. Specifically, we improve the previous arts by 1.5 AP on OVIS dataset, which features heavy occlusions, and 4.9 AP on YouTubeVIS-Long dataset, which mainly contains fast-moving objects. These results suggest that instance-level motion is robust and accurate, and hence serving as a powerful solution in complex scenarios for object-centric video segmentation.Comment: Accepted to CVPR 202