Firearm identification is an intensive and time-consuming process that requires physical interpretation of forensic ballistics evidence. Specifying the corresponding striations between bullets is expected to be helpful in this type of identification. This paper presents a method that acquires unrolled images of the bullet surfaces and emphasizes the striation of the tool mark with a Hessian matrix and finally aligns the two unrolled images based on correlation map integration. The effectiveness of the method is confirmed through experiments.
We have proposed a first-order differential type seismic displacement sensor for vibration control of anti-vibration apparatuses. This sensor is ideal for use in Direct Acceleration, Velocity and Displacement FeedBack (DAVDFB), because absolute acceleration, velocity and displacement signals are simultaneously detected. We can avoid drift problems due to integral operators which are critical in a conventional control scheme with commercial accelerometers. However, detection bandwidth of the proposed sensor is narrow to control leading-edge anti-vibration apparatuses. This paper presents bandwidth expansion in low frequency region with hybrid detector system. Since the bandwidth is limited owing to high frequency dynamics, a cause of the dynamics is determined by root locus analysis. In this process, we reveal some features of the proposed sensor comparing with second-order differential type seismic displacement sensor. As a result, the bandwidth is expanded by detecting back electromotive forces from not only a calibration coil but also a forcer coil.
In order to perform the machine work with sufficient accuracy, the position of the tool tip position be measured accurately. Tool tip detectors of CCD camera type by acquisition the image of the tool are developed. This study unveils error of the tool tip position versus tool diameter and numerical aperture of illumination optical system as object of ball end mills. Telecentric illumination system and telecentric imaging system is built by optical simulation software, ray traces of ball end mill and sphere for comparison was done. Errors occurred approximately linear for tool (sphere) diameter. For the sphere case, position errors occurred in the negative direction, indicating a tendency to increasingly underestimate target object diameter relative to the original 3D model, with increasing numerical aperture. It occurred because of refraction at the surface of the sphere. For the ball end mill case, position errors occurred in the positive direction, indicating a tendency to increasingly overestimate target object diameter relative to the original 3D model, with increasing numerical aperture. However, absolute values of errors are 1/10 of the spheres. Because the section of the tool tip has V shape and not ball shape.
It is possible to suppress a disturbance of vibration and to improve a positioning accuracy if piezoelectric device which has higher responsiveness and force density is applied to ultra-precision stage of lithography tool as a damping element. In this paper, dynamics of piezoelectric device with feedback of capacitance sensor are measured and identified to make its model and the temperature rise of the device is estimated, at first. Thereafter, two examples of vibration suppression in lithography tool are introduced and the effectiveness is verified by control simulation including the model of device.
Micro drilling operation is always exposed the risk of breakage of micro drills. Therefore, it is considered that micro drills should be rotated as accurately as possible. In the other hand, reasonable tolerance of rotating accuracy, however, should be defined for economical and engineering reason. In this paper, contact behavior of a run-out rotating drill tip with a work face is discussed according to measurement of high frequency contact force using a dynamometer. As a result, transient dynamic contact force reveals a run-out rotating drill tip is wandering just after making a contact with a work face. Wandering time depends on sliding characteristics of interface between a drill tip and a work face. For instance, centering behavior is better in drilling non-ferrous metal, where it takes 2-3 revolutions (5-7.5ms) until a drill tip stops wandering. However, it takes several times longer for hard-to-machine metals, where a drill tip diverges in the worst case . Additionally, the bending stress of a drill increases steeply with the increase of hole depth. In deep drilling, therefore, run-out of a drill must be depressed the least one for preventing drill breakage.
In order to improve the laser micro-machinability of borosilicate glass, the glass surface was doped with metal (silver or copper) ions by electric field-assisted solid-state ion exchange. Doped ions drifted and diffused into the glass substrate under a DC electric field. The drift-diffusion behavior of metal ions in glass was numerically analyzed using standard explicit finite-difference method. The calculated penetration depths of both silver and copper showed good agreement with experimentally measured values. However, there was a difference between measured and calculated ionic fluxes, especially for the early-stage of ion exchange. This discrepancy was likely to be caused by an imperfect initial contact between metal foil and glass substrate. Therefore, the increase in electric current path with ion exchange time was necessary to be taken into consideration. The modified calculation enabled more accurate estimation of ionic penetration depths.
We present a microfluidic platform for high-throughput moldless fabrication of biconvex polymer microlenses. Using a confined sheath-flowing geometry that is dry-etched on a glass chip, we produced compound droplets composed of a photocurable acrylate monomer and a non-curable silicone oil containing a surfactant. The droplets developed reproducibly and rapidly in a co-flowing aqueous stream (e.g., at∼200 drops/s). At equilibrium, the produced compound droplets formed a Janus geometry with photocurable segments having a biconvex shape, and they were monodispersed with coefficients of variation below 5%. Subsequent off-chip photopolymerization continuously yielded biconvex acrylic microlenses of uniform sizes and shapes. By varying the flow rates we could control the production rate and the size of the Janus droplets (equivalent diameter of 120-200 μm). In addition, the shape of the Janus segments and resultant particles could be tuned by varying the flow rate ratio of the two droplet phases as well as the type of surfactant dissolved in the non-curable phase. We also confirmed that the prepared biconvex microparticles could be used as optical lenses. With flexible size and shape control, low energy input, and the rapidity and scalability of the system, this technique has considerable potential as a manufacturing process for high-throughput microlens production.
This study proposes a new simulation method of workpiece shape with voxel representation for multi axis controlled machining process. Usually, voxel representation requires enormous number of computational complexity and computer memory to estimate accurate shape of machined workpiece. In this paper, a new simulation algorithm based on octree collision detection with multi level voxel representation is proposed. The proposed algorithm is designed to adapt an characteristic of GPU hardware architecture for parallel processing. In the proposed algorithm, as attribute of each voxel, block number of NC program from the moment when the voxel is machined with endmill is described in computer memory. Then, by referring the attributes, the voxeles locate near the cutting tool can be identified within a short time. By applying the proposed algorithm, the prototype simulation system is developed. The developed system can estimate shape of the workpiece in machining process within a several micro seconds at an arbitrary moments.