Zhixiang Zhao

MODELING OF MICROSTRUCTURAL EVOLUTION IN MICROALLOYED STEEL DURING HOT FORGING PROCESS

The microstructural evolution of microalloyed steel during hot forging process was investigated using physical simulation experiments. The dynamic recrystallized fraction was described by modifying Avramis equation, the parameters of which were determined by single hit compression tests. Double hit compression tests were performed to model the equation describing the static recrystallized fraction, and the obtained predicted values were in good agreement with the measured values. Austenitic grain growth was modeled as: D i n c 5 = D 0 5 + 1.6 × 10 32 t ⋅ exp ( - 716870 RT ) using isothermal tests. Furthermore, an equation describing the dynamic recrystallized grain size was given as D dyn = 3771·Z −0.2 . The models of microstructural evolution could be applied to the numerical simulation of hot forging.

Simulation study of a high‐performance brain PET system with dodecahedral geometry

Purpose In brain imaging, the spherical PET system achieves the highest sensitivity when the solid angle is concerned. However, it is not practical. In this work, we designed an alternative sphere‐like scanner, the dodecahedral scanner, which has a high sensitivity in imaging and a high feasibility to manufacture. We simulated this system and compared the performance with a few other dedicated brain PET systems. Methods Monte Carlo simulations were conducted to generate data of the dedicated brain PET system with the dodecahedral geometry (11 regular pentagon detectors). The data were then reconstructed using the in‐house developed software with the fully three‐dimensional maximum‐likelihood expectation maximization (3D‐MLEM) algorithm. Results Results show that the proposed system has a high‐sensitivity distribution for the whole field of view (FOV). With a depth‐of‐interaction (DOI) resolution around 6.67 mm, the proposed system achieves the spatial resolution of 1.98 mm. Our simulation study also shows that the proposed system improves the image contrast and reduces noise compared with a few other dedicated brain PET systems. Finally, simulations with the Hoffman phantom show the potential application of the proposed system in clinical applications. Conclusions In conclusion, the proposed dodecahedral PET system is potential for widespread applications in high‐sensitivity, high‐resolution PET imaging, to lower the injected dose.

A Novel Read-Out Electronics Design Based on 1-Bit Sigma-Delta Modulation

The conventional front-end electronics for PET imaging consist of an energy circuit and a timing circuit. A single channel in front-end electronics typically requires several amplifiers, an ADC and a TDC. In this paper, we present a novel front-end electronic design using 1-bit sigma-delta (

Development of tachyon time-of-flight PET cameras

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A novel electronics for large scale SiPM array readout and advanced PET applications

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Progresses in designing a high-sensitivity dodecahedral PET for brain imaging

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Performances of front-end electronics based on sigma-delta modulation — A simulation study

) modulation and an FPGA. The new design requires only one analog amplifier per channel. The output of the analog amplifier is read directly by the FPGA. Both the energy and timing calculation are implemented in FPGA firmware. The scope of this paper is to introduce the novel design in detail and to evaluate its performance in energy and dark current measurements. Simulink simulations were performed to validate the design with ideal components. A one-channel prototype circuit was built to assess the design with real components. The prototype circuit was tested with different input signals, including test pulses, pulse signals from a PMT detector, DC current signals and dark current signals from an SiPM sensor. Both the simulation and experimental results show that the method is inherently stable and has excellent accuracy and linearity in energy and dark current measurements. The prototype analog board was built with discrete components cost about

An object-oriented hierarchical case representation of automotive panels in a computer-aided process planning system

0.5 in total. The power consumption was about 20 mW. We conclude that the new method provides a cost-efficient and power-efficient way to accurately measure the energies of analog pulses and dark currents from detectors. The timing performance of this method is currently under evaluation.

Development of a Practical Blank Layout Optimisation System for Stamping Die Design

The increased statistical efficiency gained with TOF information can be used to decrease acquisition time, decrease injected dose, or improve image quality of a PET system. We are designing Tachyon TOF PET cameras (Tachyon I, II and III) to: (1) Construct “demonstration” single-ring TOF PET cameras that achieve significantly improved timing resolution; (2) Quantitatively measure the benefit for clinically relevant tasks as a function of timing resolution; (3) Design practical multiple-ring PET cameras with excellent timing performances for clinic applications. Tachyon I is a single-ring TOF PET scanner constructed with LYSO crystals and Hamamatsu R-9800 PMTs. The ring diameter of the scanner is 76.6 cm. Time resolution of the system (defined as of each crystal-crystal combination) is 314ps ±20ps. Tachyon I is currently in clinical test stage. Tachyon II is a single-ring SiPM-based TOF PET scanner currently under construction. The ring diameter of the scanner is still 76.6 cm. LaBr3 scintillator crystals will be used in Tachyon II. The target system-level CRT timing resolution is 100ps or better. Tachyon III is a practical multiple-ring SiPM-based TOF PET scanner for real clinic applications. Tachyon III is currently in conceptual design stage.

One-step FEM-based evaluation of weld line movement and development of blank in sheet metal stamping with tailor-welded blanks

The Silicon photomultiplier (SiPM) becomes a choice of photon sensors for advanced radiation detector development. However, reading out large-scale SiPM arrays is still a fundamental technical obstacle. We present a new method (named π-PET electronics) to address this issue. Very different from conventional front-end electronics design, the key innovation of the new electronics is to include almost all functions of front-end readout electronics inside a low-cost FPGA. That not only simplifies the analog components and reduce the cost (with only one linear amplifier) but also provides powerful and flexible signal processes to enable applying different algorithms to both enhance the performance and add new real-time dark current measurement and calibration features.