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Precision ball-end milling is widely used in the manufacture of complex microstructures. The purpose of this paper is to explore the origin of the lateral return error in an ultraprecision five-axis machine tool and its influence on a precision ball-end milling surface. First, the origin of the lateral return error of the linear axis is analyzed. Theoretical analysis and experimental results show that the root of the lateral return error is the gap variation between the slider and the guide, which is decided by the eccentric force moment acting on the hydrostatic guideway. The eccentric force moment relies on the external force and motor eccentricity. In general, the larger the eccentric force moment, the more the gap variation, and resultantly the greater the lateral return error. In addition, the lateral return error is inversely proportional to the oil supply pressure. Because the cutting forces are small enough, the cutting parameters, such as feed speed, cutting depth and cutting stepover, have little effect on the error. Secondly, the lateral return error has an important impact on the yield surface roughness, which will significantly increase the surface roughness and reduce the surface quality. Finally, the lateral return error of the hydrostatic guideway can be suppressed by compensating the machining program. The experimental results show that the surface quality of the compensated surface is significantly improved. [Display omitted] • Lateral return error originates from the gap variation of hydrostatic guideways. • Eccentric force moment and guideway stiffness influence the lateral return error. • Lateral return errors are identified by precision ball-end milling surface topographies. • Surface roughness Rq of ball-end milling is modeled with consideration of lateral return error. • A compensation method is proposed to suppress the lateral return error. [ABSTRACT FROM AUTHOR]

To assess the value of semi-quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and quantitative diffusion-weighted imaging parameters combined with human epididymis protein 4 (HE4) in predicting the pathological grade and lymphovascular space invasion (LVSI) of endometrioid adenocarcinoma (EAC). Between October 2018 and December 2021, 60 women (mean age, 55 [range, 32–77] years) with EAC underwent preoperative pelvic MRI and HE4 level measurements. The positive enhancement integral (PEI), time to peak, maximum slope of increase (MSI), and maximum slope of decrease were measured by manually drawing a region of interest on the neoplastic tissue. The receiver operating characteristic curve was used to calculate the diagnostic efficiency of the single parameter and combined factors. Lower apparent diffusion coefficients (ADCs) were observed in high-grade tumours (G3) than in low-grade tumours (G1/G2). PEI, MSI, and HE4 levels were higher in the high-grade tumours than in the low-grade tumours (p< 0.05). The area under the curve (AUC) for G3 diagnosis using multiparametric MRI combined with HE4 was 0.929. ADC values were significantly lower in the EAC with LVSI than in those without LVSI. Tumours with LVSI showed higher PEI and HE4 levels than those without LVSI (p< 0.05). The AUC for LVSI-positive diagnosis using multiparametric MRI combined with HE4 was 0.814. Semi-quantitative DCE-MRI, ADC values, and serum HE4 levels can be used to predict tumour grade and LVSI, and the prediction efficiency of multiparametric MRI combined with serum HE4 is better than that of any single factor. • Correlation of ADC value with tumour grade and LVSI of endometrioid adenocarcinoma. • To predict the pathological features of EAC using semi-quantitative DCE-MRI. • Combining MRI with HE4 to predict tumour grade and LVSI of EAC is an original idea. [ABSTRACT FROM AUTHOR]

The microstructure and chemical heterogeneity play critical roles in the magnetic performance of nanocrystalline multi-main-phase (MMP) Nd–Ce–Fe–B magnets. In this work, we report a strategy to synergistically tailor the microstructure and chemical heterogeneity of MMP magnet through optimizing sintering temperature (T s). An optimum T s of 700 °C has been obtained for nanocrystalline MMP Nd–Ce–Fe–B magnets. When sintered at T s = 700 °C, the nanocrystalline MMP magnet exhibits the maximum intrinsic coercivity H cj , the preferable remanence B r , and the resultant optimum maximum energy product (BH) max , which is attributed mainly to the appreciable density, controlled grain size, and better chemical heterogeneity. Comparably, lower or higher T s leads to the inferior magnetic properties. At lower T s below 700 °C, the poor magnetic properties are mainly due to the insufficient densification. However, at higher T s above 700 °C, the decreased H cj originates mainly from the excessive grain growth and gradual chemical homogenization. The above findings deepen our understanding on the relationship among the microstructure, chemical heterogeneity, and T s , concurrently providing an effective approach for fabricating low-cost high-performance nanocrystalline MMP Nd–Ce–Fe–B magnets. • Microstructure and chemical heterogeneity of nanocrystalline MMP Nd–Ce–Fe–B magnet are synergistically tailored. • H cj , B r , and (BH) max are simultaneously enhanced at optimum T s of 700 °C. • Dependences of microstructure and composition on T s are revealed, and an evolution model is proposed. • Mechanisms underlying changes in magnetic properties with T s are systematically analyzed. [ABSTRACT FROM AUTHOR]

Doppler broadening of positron annihilation radiation (DBAR) spectroscopy is a critical technique to provide electronic momentum information of materials. For conventional non-beam-based DBAR experiments, due to the continuous distribution of initial kinetic energy (0-545 keV) of positrons from 22Na source, two pieces of identical samples with sufficient thickness (> 1 mm for each sample with a density of 1 g/cm3) are required to stop almost all positrons in the samples. However, in many film studies, it is difficult or even impossible to meet this sample thickness requirement. In this work, judging by the output signals of a specially designed anticoincidence detector, the annihilation of positrons in a film sample and positron source are selectively collected. Furthermore, a new method is proposed to correct high-proportioned source components. Based on this, for the first time, a non-beam-based DBAR spectrometer was developed for a single piece of micron-thickness film. This approach will drastically broaden the application of DBAR spectroscopy in film characterization in future. [ABSTRACT FROM AUTHOR]

Cosmic muon imaging (muography) has gained popularity in recent years for density reconstruction in various applications. However, evaluations of image quality in reconstructed images have been lacking. This work addresses this gap by applying muon transmission imaging to a teaching building on a university campus. Multiple impacts on reconstruction image quality, including filtering methods, total counts, building thickness thresholds, and reconstruction formulas, were integrally studied. The area under the curve (AUC) of the receiver operating characteristic analysis and mean squared error (MSE) were calculated to quantitatively evaluate and optimize these parameters. Based on the simulation using the Geant4 toolkit, the recommended parameters for the building model were median filtering, a total count of 5 × 1 0 4 in the building region, a thickness threshold of 3 m, and either the constant energy loss method or cubic polynomial form fitting method. Implementing these parameters in the experimental data analysis, the reconstructed image well revealed the inner structure of the teaching building from the view angle of the detector. The optimization of the two-dimensional (2D) reconstruction method facilitates the detection of hidden cavities or regions with abnormal density in large-scale objects. [ABSTRACT FROM AUTHOR]

To precisely characterize the defects in crystalline solids including semiconductors and alloys, it is critical but challenging to improve the time resolution of positron annihilation lifetime (PAL) spectrometers. The effects of geometry and wrapping of scintillators on the time resolution of the PAL spectrometer were studied in detail. Geant4 program simulation was used to clarify the reason why cone-frustum-shaped scintillators have better time resolution than cylinder-shaped scintillators. A figure of merit was proposed to comprehensively evaluate the impacts of the transport and absorption of fluorescent photons on the time resolution of scintillators. Additionally, for the simulations of cone-frustum-shaped scintillators, polished reflective coatings can further improve the time resolution without losing count rate. Eventually, using three cone-frustum-shaped Ba F 2 scintillators and a double-stop setup, we significantly improved the time resolution of PAL spectrometer to a new record of 88.7 ps, the best time resolution up to date. This enables us to distinguish various vacancy types in crystalline solids more precisely in future. • Explained why cone-frustum-shaped scintillators have better time resolution. • Proposed a figure of merit to evaluate the time resolution of PAL spectrometer. • Achieved the best time resolution up to date for the PAL spectrometer. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime (PAL) spectroscopy has long been considered as a powerful approach to characterize atomic-scale vacancy-type defects and supermicropores, which affect the macroscopic properties of materials. In standard PAL measurements, several million annihilation events are required to achieve accuracy. For a conventional PAL spectrometer which consists of two scintillation detectors and analytical electronics, the two detectors are usually perpendicularly positioned to diminish spectra distortions (caused by backscattering and pileup). The perpendicular placement of detectors leads to a counting rate of 100 – 300 counts/second (cps) while using a 30 μ Ci 22Na source (3.3 – 10 cps/ μ Ci). Consequently, collecting one PAL spectrum with total counts of one million takes several hours. The long time limits its potential to observe changes in the microstructure. To increase the counting rate of PAL measurements, we propose a novel multi-detector PAL spectrometer, which includes three or four detectors, a digital oscilloscope, and an algorithm for any detector to record both start and stop signals. The spectrometer achieves a high counting rate of around 2144 cps (71.5 cps/ μ Ci) with four detectors, which is about ten times that of a conventional one with two detectors perpendicularly positioned. This work enables us to perform in-situ PAL measurements to disclose the minute-scale evolution of microstructure more precisely during fast physical and chemical processes in the future. • A better spectrum unfolding accuracy can be achieved with a larger total count. • The scintillator size and geometry was optimized using Geant4. • A reversible start/stop data acquisition algorithm was developed to double the counting rate. • The novel spectrometer is highly extendable to 3, 4 and more detectors. • The counting rate of ten times higher than the conventional spectrometer was obtained. [ABSTRACT FROM AUTHOR]

Oxygen-free copper components are widely used in high energy physics engineering, which are usually fabricated by the diamond machining process for achieving low roughness surface. However, the wear of diamond tool heavily affects the surface quality. In this work, the wear law of diamond tool in machining of oxygen-free copper is studied with consideration of the anisotropy of diamond strength. Firstly, the stress distribution on the tool face in machining is calculated. The results show that the cutting stress near the flank face is larger than that near the rake face. Secondly, the strength distribution of tool cutting edge is modeled. The theoretical prediction reveals that the anisotropy of diamond crystal leads to the great differences in the strength of cutting edge at different positions, and further affects the cutting edge wear resistance. Thirdly, the wear model of diamond tool is established with consideration of cutting stress distribution and tool edge strength, in which the mechanical wear is the dominant wear process. Finally, the variation of the surface roughness is analyzed on the basis of the tool wear through the cutting experiments. The experiment results indicate that the surface material deformation is closely related to the tool cutting edge wear transition area and results in different values of surface roughness. The obtained results can improve the understanding of the diamond tool wear law and estimate the diamond tool wear in machining of oxygen-free copper. [Display omitted] [ABSTRACT FROM AUTHOR]

A highly segmented muon spin rotation/relaxation/resonance (μ SR) spectrometer with over 2500 channels has been proposed in the construction of Phase II of the China Spallation Neutron Source (CSNS). Plastic scintillators are chosen as the detector material due to their high sensitivity to charged particles and good flexibility to various geometries. Gamma-ray sources are commonly used to calibrate the light yield of plastic scintillators. Accordingly, a derivative method has been developed to efficiently locate the Compton edge in gamma-ray spectra. In this method, the minimum and width of the derivative data are regarded as the position of the Compton edge and an estimation of energy resolution, respectively. Both experiments and simulations demonstrate the good reliability of this method for Compton edge positioning and energy resolution characterization. The derived Compton edge shows a systematic shift to the right of its real location. The relative shift is proportional to the energy resolution with a factor of ∼ 0.13. The assumed energy resolution should be corrected by a factor of ∼ 1.19 which is confirmed by inorganic scintillator measurements. In the measurement of plastic scintillators, the assumed Compton edge and energy resolution can well reproduce the energy response spectra for different types of gamma-ray sources. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime (PAL) spectroscopy is a powerful non-destructive method to study defects in materials. Silicon photomultipliers (SiPMs) have emerged as promising photodetector alternatives for PAL systems. However, further research is needed to fully optimize SiPM arrays for PAL applications. In this study, a dual and triple coincidence system has been developed based on four 1 × 4 SiPM arrays with resistor-chain readout, and initial results of PAL measurement have been obtained. A pixel-by-pixel time shift correction method was proposed and successfully applied using triple γ coincidence for summing 128 PAL spectra in one measurement. The system provides position, timing, and energy information for both 1275 and 511 keV γ -rays. The use of SiPM arrays and the pixel-by-pixel time shift correction method have enabled precise and reliable measurements of PALs in single-crystal silicon and yttria-stabilized zirconia samples. The developed SiPM-array-based PAL system also offers a technical solution to measure angular correlations of positron annihilation radiation, with the potential for further improvements. [ABSTRACT FROM AUTHOR]

Silicon photomultipliers (SiPMs) have great potential to replace photomultiplier tubes (PMTs) and exceed their performance in positron annihilation parameter-measurement systems. However, due to the limited active area of a single SiPM, it only covers a small γ -ray emission acceptance range and provides position information over a very small region. Using a SiPM array is a good way to overcome these problems. In this study, a resistor-chain-based SiPM detector was designed and evaluated for positron annihilation lifetime (PAL) measurements. This detector uses a 1 × 4 scintillator array, a 1 × 4 SiPM array, and a resistor-chain readout circuit to obtain position, energy, and timing information about 1275 and 511 keV γ -rays, with the readout pulses serving as both the position, energy, and timing signals. A comprehensive evaluation was conducted to assess the detector in terms of position profile, energy resolution, and time resolution. The position profiles showed that all the crystal elements in the lutetium fine silicate scintillator array were clearly resolved. The detector had an energy resolution of 11. 3 ± 0. 9 % and a time resolution of 198 ± 9 ps. A total of 32 PAL spectra were obtained using two SiPM array detectors. The PAL in yttria-stabilized zirconia (YSZ) sample was accurately verified using the summed PAL spectrum. The developed SiPM detector provides good performance for PAL measurements and could be used to build a high-performance PAL spectrometer. [ABSTRACT FROM AUTHOR]

In applications of transmission muography for large objects, plastic scintillator strips with triangular or rectangular cross-sections are frequently selected to construct imaging detectors. Triangular scintillator strips have a better position resolution over those of rectangular ones by a factor of ∼ 3.5 with the same width. The big difference has been carefully studied using Geant4. Simulations show a good agreement with those of existing muography instruments. The position resolution is influenced by the geometry (the size and base angle of triangular strips) and the energy resolution of scintillators, and angles of incoming muons. Two empirical formulas have been proposed to quantitatively estimate the position resolution with respect to the abovementioned influential factors. Perpendicularly and randomly (real angular distribution) incoming muons are considered separately in them. A more widely spread angular distribution of muons can make the position resolution worse. For commonly used triangular scintillator strips with a base angle of 45 ∘ , the ratio of the triangle base length to the position resolution is almost fixed to ∼ 12 varying the base length or energy resolution if an uncorrected Centre of Gravity (CoG) method is used. Such a ratio has a potential to be increased by a factor of ∼ 2 if the CoG method is corrected with the muon incoming angle. The influence of the energy resolution on the position resolution can be ignored. • Two empirical formulas proposed to describe the position resolution of triangular scintillators. • More widely distributed emission angles of muons lead to worse position resolution. • The ratio of triangular scintillator base length to position resolution is almost unchangeable. • The position resolution can be improved by a factor of 2 with muon emission angle corrections. • The influence of energy resolution of scintillators on the position resolution can be ignored. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime (PAL) spectroscopy is a unique method to study defects and supermicropores in solid materials. Traditionally, the pulsed slow positron beam (accelerator system included) was used to measure the PAL spectrum for a single film with a thickness of several microns, which is more complicated, expensive, and has worse time resolution than a conventional PAL spectrometer. In this paper, we developed a new PAL spectrometer to measure a single piece of micron-thickness film using two lanthanum bromide (LaBr 3) detectors, a specially designed plastic scintillator detector, and a fast digitizer, at a cost equivalent to that of a conventional PAL spectrometer. The reliability and time resolution (around 210 ps, comparable to that of a conventional PAL spectrometer) of this spectrometer were verified by testing samples with thicknesses range from 15 to 60 μ m. Due to the successful construction of the new PAL spectrometer, PAL spectroscopy can now be applied to a single piece of micron-thickness film for the first time without building an accelerator system. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime (PAL) spectroscopy is widely used in the characterization of material microstructures. It has a very high sensitivity to the material defects. This paper describes how we developed a digital PAL spectrometer with two barium fluoride (Ba F 2) detectors and reading the data with a fast digital oscilloscope. We achieved better time performance for the digital PAL spectrometer using a multi-parameter discrimination method and various pulse smoothing algorithms. With two Ba F 2 detectors in the coincidence mode, we achieved a time resolution of 160 ps for 0.511 MeV annihilation gamma rays. The multi-parameter discrimination method implemented can remove incorrect events more effectively than the conventional energy discrimination method. With this enhancement in event discrimination, the digital PAL spectrometer's time performance has improved, which results in more accurate PAL characterization. In a lifetime measurement, the PAL spectrometer's time resolution is about 130 ps, which is much better than most PAL spectrometers. With the multi-parameter discrimination method, the resolution component from the incorrect events decreases drastically, and the leading edge distortion of the PAL spectrum is significantly improved. [ABSTRACT FROM AUTHOR]

• The misfit dislocation patterns of hcp/bcc semicoherent bimetal interfaces with B and PS ORs were characterized. • The deformation mechanism of dislocation nucleation and phase transformation is revealed, where the former is closely related to dynamic evolution of misfit dislocation patterns and the latter is correlated to the specific loading mode and interface structure. • The phase transformation path for the required atomic rearrangements were revealed. • Competition relationship between non-basal dislocation nucleation and phase transformation were revealed via twisted interface models. The nucleation of lattice dislocations and interface sliding at bimetal interfaces are two fundamental mechanisms of plasticity that are responsible for the mechanical responses of nanostructured materials; however, the interface-facilitated phase transformation is rarely considered owing to its relatively high energy barrier for activation. Taking the bimetal hcp/bcc interfaces with Pitch-Schrader and Burgers orientation relationships (ORs) as an illustration, we show that both non-basal dislocation nucleation and hcp-to-bcc phase transformation can be activated at the interface under external loading when the basal slip systems are effectively suppressed. The non-basal dislocation nucleation is shown to be closely related to the dynamic evolution of misfit dislocation patterns at the semicoherent interface, in which the 1/6 [ 02 2 ¯ 3 ¯ ] pyramidal dislocation is not strictly parallel to the (01 1 ¯ 1) stacking fault plane owing to the corrugated feature. In contrast to non-basal dislocation nucleation, phase transformation requires specific crystallographic ORs of the constituent metals under certain loading conditions, which corresponds to the process of alternate shuffle and shear deformation that involves atomistic migration. To further reveal the competition between non-basal dislocation nucleation and phase transformation, a series of twisted interface models were constructed to systematically investigate the optimal condition of the interface geometry for phase transformation. The phase transformation occurred only when the dislocation nucleation was further hindered at some specific twist angles, suggesting a strong dependence of phase transformation on the interface structure. These findings provide a foundation to the atomistic mechanism of various interface-mediated deformation and a solution to tune interface-facilitated plasticity via interface engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • Li can significantly decrease the degradation rate for Mg-based and Zn-based alloys. • Both tensile and compressive strain would promote the anode dissolution rate of both Mg-based and Zn-based alloys. • Tensile and compressive strain can increase the strain energy and decrease the energy barrier of reaction. • Electron polarization between solute atoms and solvent atoms are the main causes of the change of surface properties. Using density functional theory and an improved Butler-Volmer model, we comparatively investigate the underlining mechanisms of solute alloying and mechanical straining on the electrochemical polarization and degradation behaviors of both Mg-based and Zn-based alloys. Our results suggest that some elements such as Li can potentially decrease the degradation rates for both alloys, while others like Fe, Ni, Cu, and Al, will play an opposite effect. By introducing the scaled strain energy to study the strain effect on the degradation kinetics of both alloys, we further reveal that both tensile and compressive strain would promote the degradation rate by decreasing the activation energy barrier. [ABSTRACT FROM AUTHOR]