Effects of HiPIMS Duty Cycle on Plasma Discharge and the Properties of Cu Film.

In this paper, Cu thin films were deposited on Si (100) substrates by the high-power impulse magnetron sputtering (HiIPMS) technique, and the effects of different duty cycles (from 2.25% to 5.25%) on the plasma discharge characteristics, microstructure, and electrical properties of Cu thin films were investigated. The results of the target current test show that the peak target current remains stable under 2.25% and 3% duty cycle conditions. Under the conditions of a 4.5% and 5.25% duty cycle, the target peak current shows a decreasing trend. The average power of the target shows a rising trend with the increase in the duty cycle, while the peak power of the target shows a decreasing trend with the increase in the duty cycle. The results of OES show that with the increase in the duty cycle, the total peak intensity of copper and argon emissions shows an overall increasing trend. The duty cycle from 3% to 4.5% change in copper and argon emission peak total intensity change is not obvious. The deposition rate and surface morphology of the copper film were investigated by scanning electron microscopy, and the deposition rate of the copper film increased with the increase in the duty cycle, which was mainly due to the increase in the average power. The surface roughness of the copper film was evaluated by atomic force microscopy. X-ray diffraction (XRD) was used to analyze the grain size and texture of the Cu film, and the results showed that the average grain size of the Cu film increased from 38 nm to 59 nm on the (111) and (200) crystal planes. Four-probe square resistance test copper film resistivity in 2.25%, 3% low duty cycle conditions of the copper film resistivity is generally higher than 4.5%, 5.25% high duty cycle conditions, the copper film resistivity shows the trend of change is mainly affected by the copper film grain size and the (111) face of the double effect of the optimal orientation. The lowest resistivity of the copper film measured under the 4.5% duty cycle condition is 1.7005 µΩ·cm, which is close to the intrinsic resistivity of the copper film of 1.67 µΩ·cm.

Influence of HiPIMS Pulse Widths on the Structure and Properties of Copper Films.

High-power pulse magnetron sputtering is a new type of magnetron sputtering technology that has advantages such as high peak power density and a high ionization rate compared to DC magnetron sputtering. In this paper, we report the effects of different pulse widths on the current waveform and plasma spectrum of target material sputtering, as well as the structure and properties of Cu films prepared under the same sputtering voltage and duty cycle. Extending the pulse width can make the sputtering enter the self-sputtering (SS) stage and improve the ion quantity of sputtered particles. The Cu film prepared by HiPIMS with long pulse width has higher bond strength and lower electrical resistivity compared to the Cu film prepared by short pulse width. In terms of microstructure, the Cu film prepared by HiPIMS with the long pulse width has a larger grain size and lower micro-surface roughness. When the pulse width is bigger than 200 µs, the microstructure of the Cu film changes from granular to branched. This transformation reduces the interface on the Cu film, further reducing the resistivity of the Cu film. Compared to short pulses, long pulse width HiPIMS can obtain higher quality Cu films. This result provides a new process approach for preparing high-quality Cu films using HiPIMS technology.

Study on natural frequency response characteristics of coal vibration excited by simple harmonic wave.

The natural frequency of coal is one of the important technical parameters for the application of the permeability enhancement technology of coal and rock forced vibration. Aiming at exploring the dominant frequency of the permeability enhancement technology of coal vibration excited by vibration wave, the model of coal vibration excited by simple harmonic wave (SHW) was constructed. Furthermore, considering the three main control parameters, i.e., excitation force, coal sample size and mechanical parameters, the response characteristics of coal vibration excited by SHW were simulated and calculated. The calculation results demonstrate that when the frequency of excitation force equals the natural frequency of coal, the vibration occurs and the peak values of response parameters all increase significantly. The peak acceleration response of coal increases with the increase of excitation force, whereas it decreases with the increase of coal size. Under the same SHW excitation force, the mechanical parameters of coal determine the vibration response characteristics of coal, and the natural frequency of coal is proportional to the elastic modulus. Finally, the variation law of natural frequency response characteristics of coal vibration excited by SHW was verified by the response experiment on coal vibration under SHW excitation and related test results. The research results can serve as a theoretical basis for the application of the permeability enhancement technology of coal vibration excited by vibration wave.

Correction to "Study on Temperature Variation and Pore Structure Evolution within Coal under the Effect of Liquid Nitrogen Mass Transfer".

[This corrects the article DOI: 10.1021/acsomega.1c02331.].

Study on Temperature Variation and Pore Structure Evolution within Coal under the Effect of Lilquid Nitrogen Mass Transfer.

Liquid nitrogen freezing, which is an effective permeability enhancement technology, has been applied to the extraction of oil, shale gas, and coalbed methane (CBM). This study is aimed at revealing the effect of liquid nitrogen mass transfer on the temperature variation and pore structure evolution within coal. To achieve this aim, first, temperature measurement tests under the action of liquid nitrogen freezing were conducted on saturated and dried coal samples, respectively. Next, the coal samples were subjected to nuclear magnetic resonance and computer tomography tests before and after liquid nitrogen cold soaking to further explore the mechanism of coal temperature variation from a microscopic perspective. The results show that the action of liquid nitrogen mass transfer can accelerate coal temperature variation through coal pore structure and pore water phase change. The thermal stress and frost heave force generated by liquid nitrogen cold soaking exceed the tensile strength of the coal sample, which directly causes crack initiation, expansion, and connection. The mass transfer of liquid nitrogen has a significant promoting effect on pore development. This study provides the technical support necessary for the efficient exploitation of CBM resources and the improvement of CBM extraction rate.

Variation features of unfrozen water content of water-saturated coal under low freezing temperature.

To determine the unfrozen water content variation characteristics of coal from the low temperature freezing based on the good linear relationship between the amplitude of the nuclear magnetic resonance (NMR) signal and movable water, pulsed NMR technology was used to test water-saturated coal samples and analyze the relationship between the unfrozen water content, the temperature and pore pressure during freeze-thaw from a microscopic perspective. Experimental results show that the swelling stress of the ice destroys the original pore structure during the freezing process, causing the melting point of the pore ice to change, so the unfrozen water content during the melting process presents a hysteresis phenomenon. When phase equilibrium has been established in the freezing process, the unfrozen water is mainly the film water on the pore surface and pore water in pores with pore radius below 10 nm. At this time, the freezing point of the water in the system decreases exponentially as the temperature increases. The micropores of the coal samples from the Jiulishan Coalmine are well-developed, and the macropores and fractures are relatively small, with most pores having a pore radius between 0.1 and 10 nm. The pore water freezing point gradually decreases with the pore radius. When the pore radius decreases to 10 nm, the freezing point of pore water starts to decrease sharply with the decreasing pore radius. When the pore radius reaches 1.54 nm, the pore water freezing point changes as fast as 600 ℃/nm.

Photoelectric scanning-based resection method for mobile robot localization.

Indoor localization is a key enabling technology for mobile robot navigation in industrial manufacturing. As a distributed metrology system based on multi-station intersection measurement, the workshop measurement positioning system (wMPS) is gaining increasing attention in mobile robot localization. In this paper, a new, to the best of our knowledge, wMPS-based resection localization method is proposed using a single onmidirectional transmitter mounted on a mobile robot with scanning photoelectric receivers distributed in the work space. Compared to the traditional method that requires multiple stationary transmitters, our new method provides higher flexibility and cost-effectiveness. The position and orientation of the mobile robot are then iteratively optimized with respect to the constraint equations. In order to obtain the optimal solution rapidly, two methods of initial value determination are presented for different numbers of effective receivers. The propagation of the localization uncertainty is also investigated using Monte-Carlo simulations. Moreover, two experiments of automated guided vehicle localization are conducted, and the results demonstrate the high accuracy of the proposed method.

A Sub-Regional Calibration Method That Can Accomplish Error Compensation for Photoelectric Scanning Measurement Network.

In the measurement process of photoelectric scanning measurement network, the laser surface edge area has lower measurement accuracy than the middle area due to the geometrical distortions of the laser surface of the transmitter. This paper presents a sub-regional calibration method that can accomplish error compensation for the measurement system. Unlike the camera sub-regional calibration, the regional division and identification of the laser surface are more difficult. In this paper, the pitch angle in the transmitter coordinate frame of the spatial point was used as the basis for the division and identification of the laser surface. In the calibration process, the laser surface of the transmitter was divided into different regions and each region was calibrated independently, so that an intrinsic parameters database containing the intrinsic parameters of different regions could be established. Based on the database, the region identification and error compensation algorithm were designed, and comparison experiments were carried out. With the novel calibration method, the measurement accuracy of the system had an obvious upgrade, especially at the edges of the laser surface within a certain measurement area, which could enlarge the effective measurement area of the transmitter and would broaden and deepen the application fields of photoelectric scanning measurement network.

A Multi-Camera Rig with Non-Overlapping Views for Dynamic Six-Degree-of-Freedom Measurement.

Large-scale measurement plays an increasingly important role in intelligent manufacturing. However, existing instruments have problems with immersive experiences. In this paper, an immersive positioning and measuring method based on augmented reality is introduced. An inside-out vision measurement approach using a multi-camera rig with non-overlapping views is presented for dynamic six-degree-of-freedom measurement. By using active LED markers, a flexible and robust solution is delivered to deal with complex manufacturing sites. The space resection adjustment principle is addressed and measurement errors are simulated. The improved Nearest Neighbor method is employed for feature correspondence. The proposed tracking method is verified by experiments and results with good performance are obtained.

Identification and comparative analysis of microRNAs in barnyardgrass (Echinochloa crus-galli) in response to rice allelopathy.

Rice allelopathy is a hot topic in the field of allelopathy, and behaviour of donor allelopathic rice has been well documented. However, few study addresses response of receiver barnyardgrass (BYG). We found that expression of miRNAs relevant to plant hormone signal transduction, nucleotide excision repair and the peroxisome proliferator-activated receptor and p53 signalling pathways was enhanced in BYG co-cultured with the allelopathic rice cultivar PI312777, the expression levels of these miRNAs in BYG plants were positively correlated with allelopathic potential of the co-cultured rice varieties. Treatment of BYG plants with rice-produced phenolic acids also increased miRNA expression in BYG, while treatment with rice-produced terpenoids had no obvious effect on miRNA expression. In the hydroponic system, the largest number of Myxococcus sp. was found in the growth medium containing rice with the highest allelopathic potential. The addition of phenolic acids in the hydroponic medium also increased the number of Myxococcus sp. More interestingly, inoculation with Myxococcus xanthus significantly increased miRNA expression in the treated BYG. Jointed treatments of ferulic acid and M. xanthus led to strongest growth inhibition of BYG. The results suggest that there exist involvement of Myxococcus sp. and mediation of miRNA expression in rice allelopathy against BYG.

Flying spot laser triangulation scanner using lateral synchronization for surface profile precision measurement.

High-speed surface profile measurement with high precision is crucial for target inspection and quality control. In this study, a laser scanner based on a single point laser triangulation displacement sensor and a high-speed rotating polygon mirror is proposed. The autosynchronized scanning scheme is introduced to alleviate the trade-off between the field of view and the range precision, which is the inherent deficiency of the conventional triangulation. The lateral synchronized flying spot technology has excellent characteristics, such as programmable and larger field of view, high immunity to ambient light or secondary reflections, high optical signal-to-noise ratio, and minimum shadow effect. Owing to automatic point-to-point laser power control, high accuracy and superior data quality are possible when measuring objects featuring varying surface characteristics even in demanding applications. The proposed laser triangulation scanner is validated using a laboratory-built prototype and practical considerations for design and implementation of the system are described, including speckle noise reduction method and real-time signal processing. A method for rapid and accurate calibration of the laser triangulation scanner using lookup tables is also devised, and the system calibration accuracy is generally smaller than ±0.025 mm. Experimental results are presented and show a broad application prospect for fast surface profile precision measurement.

A vision-based self-calibration method for robotic visual inspection systems.

A vision-based robot self-calibration method is proposed in this paper to evaluate the kinematic parameter errors of a robot using a visual sensor mounted on its end-effector. This approach could be performed in the industrial field without external, expensive apparatus or an elaborate setup. A robot Tool Center Point (TCP) is defined in the structural model of a line-structured laser sensor, and aligned to a reference point fixed in the robot workspace. A mathematical model is established to formulate the misalignment errors with kinematic parameter errors and TCP position errors. Based on the fixed point constraints, the kinematic parameter errors and TCP position errors are identified with an iterative algorithm. Compared to the conventional methods, this proposed method eliminates the need for a robot-based-frame and hand-to-eye calibrations, shortens the error propagation chain, and makes the calibration process more accurate and convenient. A validation experiment is performed on an ABB IRB2400 robot. An optimal configuration on the number and distribution of fixed points in the robot workspace is obtained based on the experimental results. Comparative experiments reveal that there is a significant improvement of the measuring accuracy of the robotic visual inspection system.

Near real-time immuno-optical sensor for diagnosing single point mutation: a model system: sensor for factor V Leiden diagnosis.

Factor V leiden (FVL) is an abnormality of factor V (FV), a blood coagulation factor. It is a hereditary blood coagulation disorder with a high frequency (3-7% of general population). The most common type of FVL is caused by a single amino acid mutation and, therefore, its diagnosis is currently done only by DNA analysis, which takes a long time and is expensive. We have developed a rapid, accurate, and cost-effective, sandwich immuno-optical sensing method. To produce monoclonal antibodies against FV or FVL, having minimal cross-reactivity with the other molecule, a 20 amino acid sequence (20-mer) of FV or FVL at around the mutation site was utilized. The antibodies were screened first with the 20-mers and then the ones showing no cross-affinity were reacted with native FV or FVL molecules and they showed some cross-reactivity. Using two antibodies having strongest affinity to either FV or FVL molecule, a FV and a FVL preferred sensors, were produced. After verifying that the levels of the antibody affinity to the two different molecules remained constant with changes in analyte concentration, a two-sensor system is developed to quantify FV and FVL in plasma samples. The system quantified the levels of FV and FVL at the maximum error of 0.5 microg/ml-plasma, in their physiological concentration range of 0-12 microg/ml-plasma. The levels of both molecules may provide us whether the patient has FVL or not but also the seriousness level of the disease (homozygous and different level of heterozygous).

Biosensor for diagnosing Factor V Leiden, a single amino acid mutated abnormality of Factor V.

Factor V Leiden (FVL) is an abnormality with a single amino acid mutation of Factor V (FV) and is the most common, hereditary blood coagulation disorder. FVL is currently diagnosed by DNA analysis, which takes a long assay time, high cost, and a specially trained person. We are developing a rapid, accurate, and cost-effective biosensing system to quantify both FV and FVL in blood plasma, to diagnose FVL and also to evaluate the seriousness of the disease status. This system is based on a sandwich immuno-reaction on an optical fiber. To produce the monoclonal antibody against only FV or only FVL without cross-reacting with the other molecule and with a higher probability, a 20 amino acid sequence (20-mer) of FV or FVL around the mutation region was injected into mice and then hybridoma cell lines specific to each 20-mer were selected. When these antibodies were tested with native FV or FVL molecules, they were found to be cross-reacting with the other molecules, but some with higher affinity to FV (FV preferred) and some to FVL (FVL preferred). Using these antibodies, two different sensors were developed: FV preferred and FVL preferred sensors. These two sensors allowed us to quantify FV and FVL in plasma with a maximum error of 4%. The plasma levels of both molecules provide us not only FVL diagnosis but also the level of the seriousness. The same principles may be used for developing diagnostic tools for other diseases with a single point mutation.

Highly sensitive rapid, reliable, and automatic cardiovascular disease diagnosis with nanoparticle fluorescence enhancer and mems.

Cardiovascular diseases (CVDs) have been the leading threat to human life. An effective way for sensitive and accurate CVD diagnosis is to measure the biochemical markers released from the damaged myocardial cells in the bloodstream. Here, a multi-analyte, fluorophore mediated, fiber-optic immuno-biosensing system is being developed to simultaneously and rapidly quantify four clinically important cardiac markers, myoglobin, C-reactive protein, cardiac troponin I, and B-type natriuretic peptide. To quantify these markers at a pico-molar level, novel nanoparticle reagents enhancing fluorescence were used and signal enhancement was obtained as high as approximately 230%. Micro-electro-mechanical system (MEMS) was integrated to this system to ensure a reliable and fully-automated sensing performance. A point-of-care, automatic microfluidic sensing system for four cardiac marker quantification was developed with the properties of 3 cm sensor size, 300 microL sample volume, 9-minute assay time, and an average signal-to-noise ratio of 35.

Real-time, automated, fluorophore mediated multi-cardiac marker biosensing system with nano-metallic particle reagent.

Cardiovascular disease (CVD) is the leading cause of death in U.S. Early and accurate diagnosis of CVD is crucial to save many lives, especially for the patients suffering the heart attack. Accurate and fast quantification of cardiac muscle specific biomarkers in the blood enables accurate diagnosis and prognosis and timely treatment of the patients. A prototype of fiber-optic, multi-analyte, immuno-biosensing system integrated with an automatic flow control unit has been in development to quantify four important cardiac markers in blood plasma accurately, rapidly and simultaneously. The validity of the sensor was, however, challenged because the concentrations of two markers are only at tens of picomolar level. Here, plasmon rich nano-metallic particles and selected biocompatible solvents were developed for fluorescence enhancement to improve the sensitivity of our fluorophore mediated biosensing. By applying the nanometal particle and the solvent, the sensitivity of single cardiac marker sensors were increased by 1.5 - 3 times. By using the fluorescence enhancing nano-metallic particle reagents, simultaneous quantification of four cardiac markers in plasma is currently possible, using 3-cm-sensor within 10 minutes at an average signal-to-noise ratio of 20.

Fluorophore-mediated, fiber-optic, multi-analyte, immunosensing system for rapid diagnosis and prognosis of cardiovascular diseases.

A prototype of a fiber-optic, multi-analyte, immunobiosensing system was developed to simultaneously quantify disease-representing biomarkers in blood plasma. This system was for simultaneous quantification of two different groups of multi-biomarkers related to cardiovascular diseases (CVD): anticoagulants (protein C, protein S, antithrombin III, and plasminogen) for deficiency diagnosis; and cardiac markers (B-type natriuretic peptide, cardiac troponin I, myoglobin, and C-reactive protein) for coronary heart disease diagnosis. As an initial effort towards the development of a disposable and easy-to-use sensing cartridge as a rapid diagnostic tool for CVD related diseases, a prototype of a flow control system was also developed to automatically perform simultaneous four-analyte quantification. Currently, the system is capable of quantifying the multiple anticoagulants in their clinically significant sensing ranges within 5 minutes, at an average signal-to-noise (S/N) ratio of 25. A simultaneous assay of the four cardiac markers can be performed within 10 min, at an average S/N ratio of 20. When this highly portable multi-analyte sensing system is completed and successfully tested for CVD patient's plasma, it can provide rapid (<10 min) and reliable diagnostic and prognostic information at a patient's bedside.