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Yang, Jun

Publications and source records attributed to Yang, Jun.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Effect of MoSi{sub 2} Content on Dry Sliding Tribological Properties of Zr-Based Bulk Metallic Glass Composites

Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} bulk metallic glass and its composites were prepared by suction casting into a copper mold. The effect of MoSi{sub 2} content on the tribological behavior of Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} BMG was studied by using a high-speed reciprocating friction and wear tester. The results indicate that the friction coefficient and wear resistance of the BMGs can be improved by a certain amount of crystalline phase induced by MoSi{sub 2} content from 1 to 3% and deteriorated with MoSi{sub 2} content of 4%. The wear mechanism of both the metallic glass and its composite is abrasive wear. The mechanism of crystalline phase-dependent tribological properties of the composite was discussed based on the wear track and mechanical properties in the present work. The wear behavior of Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} BMG and its composite indicates that a good combination of the toughness and the hardness can make the composite be well wear resistant.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Precise control of alloying sites of bimetallic nanoclusters via surface motif exchange reaction

Here, precise control of alloying sites has long been a challenging pursuit, yet little has been achieved for the atomic-level manipulation of metallic nanomaterials. Here we describe utilization of a surface motif exchange (SME) reaction to selectively replace the surface motifs of parent [Ag 44 (SR) 30 ] 4– (SR = thiolate) nanoparticles (NPs), leading to bimetallic NPs with well-defined molecular formula and atomically-controlled alloying sites in protecting shell. A systematic mass (and tandem mass) spectrometry analysis suggests that the SME reaction is an atomically precise displacement of SR–Ag(I)–SR-protecting modules of Ag NPs by the incoming SR–Au(I)–SR modules, giving rise to a core-shell [Ag 32 @Au 12 (SR) 30 ] 4– . Theoretical calculation suggests that the thermodynamically less favorable core-shell Ag@Au nanostructure is kinetically stabilized by the intermediate Ag 20 shell, preventing inward diffusion of the surface Au atoms. The delicate SME reaction opens a door to precisely control the alloying sites in the protecting shell of bimetallic NPs with broad utility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Tuning Nb–Pt Interactions To Facilitate Fuel Cell Electrocatalysis

High stability, availability of multiple oxidation states, and accessibility within a wide electrochemical window are the prime features of Nb that make it a favorable candidate for electrocatalysis, especially when it is combined with Pt. However, Nb has been used as a support in the form of oxides in all previously reported Pt–Nb electrocatalysts, and no Pt–Nb alloying phase has been demonstrated hitherto. Herein, we report a multifunctional Pt–Nb composite (PtNb/NbOx-C) where Nb exists both as an alloying component with Pt and as an oxide support and is synthesized by means of a simple wet chemical method. In this work, the Pt–Nb alloy phase has been firmly verified with the help of multiple spectroscopic methods. This allows for the experimental evidence of the theoretical prediction that Pt–Nb alloy interactions improve the oxygen reduction reaction (ORR) activity of Pt. In addition, such a combination of multiphase Nb brings up myriad features encompassing increased ORR durability, immunity to phosphate anion poisoning, enhanced hydrogen oxidation reaction (HOR) activity, and oxidative carbon monoxide (CO) stripping, making this electrocatalyst useful in multiple fuel cell systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Crystal structure of a multi-domain human smoothened receptor in complex with a super stabilizing ligand

Here, the Smoothened receptor (SMO) belongs to the Class Frizzled of the G protein-coupled receptor (GPCR) superfamily, constituting a key component of the Hedgehog signalling pathway. Here we report the crystal structure of the multi-domain human SMO, bound and stabilized by a designed tool ligand TC114, using an X-ray free-electron laser source at 2.9 Å. The structure reveals a precise arrangement of three distinct domains: a seven-transmembrane helices domain (TMD), a hinge domain (HD) and an intact extracellular cysteine-rich domain (CRD). This architecture enables allosteric interactions between the domains that are important for ligand recognition and receptor activation. By combining the structural data, molecular dynamics simulation, and hydrogen-deuterium-exchange analysis, we demonstrate that transmembrane helix VI, extracellular loop 3 and the HD play a central role in transmitting the signal employing a unique GPCR activation mechanism, distinct from other multi-domain GPCRs.

36 MATERIALS SCIENCE↗
DOE OSTI2017

LiMnPO4·Li3V2(PO4)3 composite cathode material derived from Mn(VO3)2 nanosheet precursor

The LiMnPO4·Li3V2(PO4)3/C composite cathode material was synthesized from Mn(VO3)2 nanosheet precursor, which was prepared by a hydrothermal method. The structure and morphology of the composite were systematically investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and scanning transmission electron microscopy (STEM), etc. The LiMnPO4·Li3V2(PO4)3/C composite material exhibits a low polarization and high specific capacity of 150.7 mAh g-1 at 0.1C in voltage range of 2.5–4.5V, and excellent cycle and rate performance for its stable nanocomposite framework. The composite material dominantly exists in the morphological shape of nanograins and nanorods, which increases the surface area and hence facilitate the electrolyte penetration. The nanoparticle components were even further identified in detail.

Lei, Zhihong↗
DOE OSTI2016

Pseudomonas aeruginosa sabotages the generation of host proresolving lipid mediators

Recurrent Pseudomonas aeruginosa infections coupled with robust, damaging neutrophilic inflammation characterize the chronic lung disease cystic fibrosis (CF). The proresolving lipid mediator, 15-epi lipoxin A 4 (15-epi LXA 4 ), plays a critical role in limiting neutrophil activation and tissue inflammation, thus promoting the return to tissue homeostasis. In this work w we show that a secreted P. aeruginosa epoxide hydrolase, cystic fibrosis transmembrane conductance regulator inhibitory factor (Cif), can disrupt 15-epi LXA 4 transcellular biosynthesis and function. In the airway, 15-epi LXA 4 production is stimulated by the epithelial-derived eicosanoid 14,15-epoxyeicosatrienoic acid (14,15-EET). Cif sabotages the production of 15-epi LXA 4 by rapidly hydrolyzing 14,15-EET into its cognate diol, eliminating a proresolving signal that potently suppresses IL-8–driven neutrophil transepithelial migration in vitro. Retrospective analyses of samples from patients with CF supported the translational relevance of these preclinical findings. Elevated levels of Cif in bronchoalveolar lavage fluid were correlated with lower levels of 15-epi LXA 4 , increased IL-8 concentrations, and impaired lung function. Together, these findings provide structural, biochemical, and immunological evidence that the bacterial epoxide hydrolase Cif disrupts resolution pathways during bacterial lung infections. The data also suggest that Cif contributes to sustained pulmonary inflammation and associated loss of lung function in patients with CF

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Efficient Discovery of Novel Multicomponent Mixtures for Hydrogen Storage: A Combined Computational/Experimental Approach

The objective of the proposed program is to discover novel mixed hydrides for hydrogen storage, which enable the DOE 2010 system-level goals. Our goal is to find a material that desorbs 8.5 wt.% H 2 or more at temperatures below 85°C. The research program will combine first-principles calculations of reaction thermodynamics and kinetics with material and catalyst synthesis, testing, and characterization. We will combine materials from distinct categories (e.g., chemical and complex hydrides) to form novel multicomponent reactions. Systems to be studied include mixtures of complex hydrides and chemical hydrides [e.g. LiNH 2+ NH 3 BH 3 ] and nitrogen-hydrogen based borohydrides [e.g. Al(BH 4 ) 3 (NH 3 ) 3 ]. The 2010 and 2015 FreedomCAR/DOE targets for hydrogen storage systems are very challenging, and cannot be met with existing materials. The vast majority of the work to date has delineated materials into various classes, e.g., complex and metal hydrides, chemical hydrides, and sorbents. However, very recent studies indicate that mixtures of storage materials, particularly mixtures between various classes, hold promise to achieve technological attributes that materials within an individual class cannot reach. Our project involves a systematic, rational approach to designing novel multicomponent mixtures of materials with fast hydrogenation/dehydrogenation kinetics and favorable thermodynamics using a combination of state-of-the-art scientific computing and experimentation. We will use the accurate predictive power of first-principles modeling to understand the thermodynamic and microscopic kinetic processes involved in hydrogen release and uptake and to design new material/catalyst systems with improved properties. Detailed characterization and atomic-scale catalysis experiments will elucidate the effect of dopants and nanoscale catalysts in achieving fast kinetics and reversibility. And, state-of-the-art storage experiments will give key storage attributes of the investigated reactions, validate computational predictions, and help guide and improve computational methods. In sum, our approach involves a powerful blend of: 1) H2 Storage measurements and characterization, 2) State-of-the-art computational modeling, 3) Detailed catalysis experiments, 4) In-depth automotive perspective.

08 HYDROGEN↗
DOE OSTI2016

TRACING THE LOWEST PROPELLER LINE IN MAGELLANIC HIGH-MASS X-RAY BINARIES

We have combined the published observations of high-mass X-ray binary (HMXB) pulsars in the Magellanic Clouds with a new processing of the complete archival data sets from the XMM-Newton and Chandra observatories in an attempt to trace the lowest propeller line below which accretion to polar caps is inhibited by the centrifugal force and the pulsations from the most weakly magnetized pulsars cease. Previously published data reveal that some of the faster-spinning pulsars with spin periods of P {sub S} < 12 s, detected at relatively low X-ray luminosities L {sub X} , appear to define such a line in the P {sub S} – L {sub X} diagram, characterized by a magnetic moment of μ = 3 × 10{sup 29} G cm{sup 3}. This value implies the presence of surface magnetic fields of B ≥ 3 × 10{sup 11} G in the compact objects of this class. Only a few quiescent HMXBs are found below the propeller line: LXP4.40 and SXP4.78, for which XMM-Newton and Chandra null detections respectively placed firm upper limits on their X-ray fluxes in deep quiescence; and A0538-66, for which many sub-Eddington detections have never measured any pulsations. On the other hand, the data from the XMM-Newton and Chandra archives show clearly that, during routine observation cycles, several sources have been detected below the propeller line in extremely faint, nonpulsating states that can be understood as the result of weak magnetospheric emission when accretion to the poles is centrifugally stalled or severely diminished. We also pay attention to the anomalous X-ray pulsar CXOU J010043.1-721134 that was reported in HMXB surveys. Its pulsations and locations near and above the propeller line indicate that this pulsar could be accreting from a fossil disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Sinomenine attenuates renal fibrosis through Nrf2-mediated inhibition of oxidative stress and TGFβ signaling

Renal fibrosis is the common feature of chronic kidney disease and mainly mediated by TGFβ-associated pro-fibrogenic signaling, which causes excessive extracellular matrix accumulation and successive loss of kidney functions. Sinomenine (SIN), an alkaloid derived from medicinal herb extensively used in treatment of rheumatoid arthritis and various inflammatory disorders, displays renal protective properties in experimental animals; however its pharmacological potency against renal fibrosis is not explored. In this study we report that SIN possesses strong anti-renal fibrosis functions in kidney cell and in mouse fibrotic kidney. SIN beneficially modulated the pro-fibrogenic protein expression in TGFβ-treated kidney cells and attenuated the renal fibrotic pathogenesis incurred by unilateral ureteral obstruction (UUO), which correlated with its activation of Nrf2 signaling - the key defender against oxidative stress with anti-fibrotic potentials. Further investigation on its regulation of Nrf2 downstream events revealed that SIN significantly balanced oxidative stress via improving the expression and activity of anti-oxidant and detoxifying enzymes, and interrupted the pro-fibrogenic signaling of TGFβ/Smad and Wnt/β-catenin. Even more impressively SIN achieved its anti-fibrotic activities in an Nrf2-dependent manner, suggesting that SIN regulation of Nrf2-associated anti-fibrotic activities constitutes a critical component of SIN's renoprotective functions. Collectively our studies have demonstrated a novel anti-fibrotic property of SIN and its upstream events and provided a molecular basis for SIN's potential applications in treatment of renal fibrosis-associated kidney disorders. - Highlights: • Sinomenine has strong potency of inhibiting renal fibrosis in UUO mouse kidney. • Sinomenine attenuates the expression of profibrogenic proteins. • Sinomenine balances renal fibrosis-associated oxidative stress. • Sinomenine mitigates profibrogenic signaling of TGBβ/Smad and Wnt/β-catenin. • Sinomenine exerts anti-renal fibrotic functions mainly via activating Nrf2 pathways.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

DIFFERENCES IN WATER VAPOR RADIATIVE TRANSFER AMONG 1D MODELS CAN SIGNIFICANTLY AFFECT THE INNER EDGE OF THE HABITABLE ZONE

An accurate estimate of the inner edge of the habitable zone is critical for determining which exoplanets are potentially habitable and for designing future telescopes to observe them. Here, we explore differences in estimating the inner edge among seven one-dimensional radiative transfer models: two line-by-line codes (SMART and LBLRTM) as well as five band codes (CAM3, CAM4-Wolf, LMDG, SBDART, and AM2) that are currently being used in global climate models. We compare radiative fluxes and spectra in clear-sky conditions around G and M stars, with fixed moist adiabatic profiles for surface temperatures from 250 to 360 K. We find that divergences among the models arise mainly from large uncertainties in water vapor absorption in the window region (10 μ m) and in the region between 0.2 and 1.5 μ m. Differences in outgoing longwave radiation increase with surface temperature and reach 10–20 W m{sup 2}; differences in shortwave reach up to 60 W m{sup 2}, especially at the surface and in the troposphere, and are larger for an M-dwarf spectrum than a solar spectrum. Differences between the two line-by-line models are significant, although smaller than among the band models. Our results imply that the uncertainty in estimating the insolation threshold of the inner edge (the runaway greenhouse limit) due only to clear-sky radiative transfer is ≈10% of modern Earth’s solar constant (i.e., ≈34 W m{sup 2} in global mean) among band models and ≈3% between the two line-by-line models. These comparisons show that future work is needed that focuses on improving water vapor absorption coefficients in both shortwave and longwave, as well as on increasing the resolution of stellar spectra in broadband models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Dosimetric evaluation of 4 different treatment modalities for curative-intent stereotactic body radiation therapy for isolated thoracic spinal metastases

To investigate the dosimetric characteristics of 4 SBRT-capable dose delivery systems, CyberKnife (CK), Helical TomoTherapy (HT), Volumetric Modulated Arc Therapy (VMAT) by Varian RapidArc (RA), and segmental step-and-shoot intensity-modulated radiation therapy (IMRT) by Elekta, on isolated thoracic spinal lesions. CK, HT, RA, and IMRT planning were performed simultaneously for 10 randomly selected patients with 6 body types and 6 body + pedicle types with isolated thoracic lesions. The prescription was set with curative intent and dose of either 33 Gy in 3 fractions (3F) or 40 Gy in 5F to cover at least 90% of the planning target volume (PTV), correspondingly. Different dosimetric indices, beam-on time, and monitor units (MUs) were evaluated to compare the advantages/disadvantages of each delivery modality. In ensuring the dose-volume constraints for cord and esophagus of the premise, CK, HT, and RA all achieved a sharp conformity index (CI) and a small penumbra volume compared to IMRT. RA achieved a CI comparable to those from CK, HT, and IMRT. CK had a heterogeneous dose distribution in the target as its radiosurgical nature with less dose uniformity inside the target. CK had the longest beam-on time and the largest MUs, followed by HT and RA. IMRT presented the shortest beam-on time and the least MUs delivery. For the body-type lesions, CK, HT, and RA satisfied the target coverage criterion in 6 cases, but the criterion was satisfied in only 3 (50%) cases with the IMRT technique. For the body + pedicle-type lesions, HT satisfied the criterion of the target coverage of ≥90% in 4 of the 6 cases, and reached a target coverage of 89.0% in another case. However, the criterion of the target coverage of ≥90% was reached in 2 cases by CK and RA, and only in 1 case by IMRT. For curative-intent SBRT of isolated thoracic spinal lesions, RA is the first choice for the body-type lesions owing to its delivery efficiency (time); the second choice is CK or HT; HT is the preferential choice for the body + pedicle-type lesions. This study suggests further clinical investigations with longer follow-up for these studied cases.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

The most luminous heavily obscured quasars have a high merger fraction: morphological study of wise -selected hot dust-obscured galaxies

Previous studies have shown that Wide-field Infrared Survey Explorer -selected hyperluminous, hot dust-obscured galaxies (Hot DOGs) are powered by highly dust-obscured, possibly Compton-thick active galactic nuclei (AGNs). High obscuration provides us a good chance to study the host morphology of the most luminous AGNs directly. We analyze the host morphology of 18 Hot DOGs at z ∼ 3 using Hubble Space Telescope /WFC3 imaging. We find that Hot DOGs have a high merger fraction (62 ± 14%). By fitting the surface brightness profiles, we find that the distribution of Sérsic indices in our Hot DOG sample peaks around 2, which suggests that most Hot DOGs have transforming morphologies. We also derive the AGN bolometric luminosity (∼10{sup 14} L {sub ⊙}) of our Hot DOG sample by using IR spectral energy distributions decomposition. The derived merger fraction and AGN bolometric luminosity relation is well consistent with the variability-based model prediction. Both the high merger fraction in an IR-luminous AGN sample and relatively low merger fraction in a UV/optical-selected, unobscured AGN sample can be expected in the merger-driven evolutionary model. Finally, we conclude that Hot DOGs are merger-driven and may represent a transit phase during the evolution of massive galaxies, transforming from the dusty starburst-dominated phase to the unobscured QSO phase.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Characterization of DWARF14 Genes in Populus

Strigolactones are a new class of plant hormones regulating shoot branching and symbiotic interactions with arbuscular mycorrhizal fungi. Studies of branching mutants in herbaceous plants have identified several key genes involved in strigolactone biosynthesis or signaling. The strigolactone signal is perceived by a member of the α/β-fold hydrolase superfamily, known as DWARF14 (D14). However, little is known about D14 genes in the woody perennial plants. Here we report the identification of D14 homologs in the model woody plant Populus trichocarpa. We showed that there are two D14 homologs in P. trichocarpa, designated as PtD14a and PtD14b that are over 95% similar at the amino acid level. Expression analysis indicated that the transcript level of PtD14a is generally more abundant than that of PtD14b. However, only PtD14a was able to complement Arabidopsis d14 mutants, suggesting that PtD14a is the functional D14 ortholog. Amino acid alignment and structural modeling revealed substitutions of several highly conserved amino acids in the PtD14b protein including a phenylalanine near the catalytic triad of D14 proteins. Ultimately, we find this study lays a foundation for further characterization of strigolactone pathway and its functions in the woody perennial plants.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Prostate extracellular vesicles in patient plasma as a liquid biopsy platform for prostate cancer using nanoscale flow cytometry

Background: Extracellular vesicles released by prostate cancer present in seminal fluid, urine, and blood may represent a non-invasive means to identify and prioritize patients with intermediate risk and high risk of prostate cancer. We hypothesize that enumeration of circulating prostate microparticles (PMPs), a type of extracellular vesicle (EV), can identify patients with Gleason Score≥4+4 prostate cancer (PCa) in a manner independent of PSA. Patients and Methods: Plasmas from healthy volunteers, benign prostatic hyperplasia patients, and PCa patients with various Gleason score patterns were analyzed for PMPs. We used nanoscale flow cytometry to enumerate PMPs which were defined as submicron events (100-1000nm) immunoreactive to anti-PSMA mAb when compared to isotype control labeled samples. Levels of PMPs (counts/µL of plasma) were also compared to CellSearch CTC Subclasses in various PCa metastatic disease subtypes (treatment naïve, castration resistant prostate cancer) and in serially collected plasma sets from patients undergoing radical prostatectomy. Results: PMP levels in plasma as enumerated by nanoscale flow cytometry are effective in distinguishing PCa patients with Gleason Score≥8 disease, a highrisk prognostic factor, from patients with Gleason Score≤7 PCa, which carries an intermediate risk of PCa recurrence. PMP levels were independent of PSA and significantly decreased after surgical resection of the prostate, demonstrating its prognostic potential for clinical follow-up. CTC subclasses did not decrease after prostatectomy and were not effective in distinguishing localized PCa patients from metastatic PCa patients. Conclusions: PMP enumeration was able to identify patients with Gleason Score ≥8 PCa but not patients with Gleason Score 4+3 PCa, but offers greater confidence than CTC counts in identifying patients with metastatic prostate cancer. CTC Subclass analysis was also not effective for post-prostatectomy follow up and for distinguishing metastatic PCa and localized PCa patients. Nanoscale flow cytometry of PMPs presents an emerging biomarker platform for various stages of prostate cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Cu-doped CdS and its application in CdTe thin film solar cell

Cu is widely used in the back contact formation of CdTe thin film solar cells. However, Cu is easily to diffuse from the back contact into the CdTe absorber layer and even to the cell junction interface CdS/CdTe. This phenomenon is generally believed to be the main factor affecting the CdTe solar cell stability. In this study Cu was intentionally doped in CdS thin film to study its effect on the microstructural, optical and electrical properties of the CdS material. Upon Cu doping, the V{sub Cd{sup −}} and the surface-state-related photoluminescence emissions were dramatically decreased/quenched. The presence of Cu atom hindered the recrystallization/coalescence of the nano-sized grains in the as-deposited CdS film during the air and the CdCl{sub 2} annealing. CdTe thin film solar cell fabricated with Cu-doped CdS window layers demonstrated much decreased fill factor, which was induced by the increased space-charge recombination near the p-n junction and the worsened junction crystalline quality. Temperature dependent current-voltage curve measurement indicated that the doped Cu in the CdS window layer was not stable at both room and higher temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Omeprazole increases the efficacy of a soluble epoxide hydrolase inhibitor in a PGE{sub 2} induced pain model

Epoxyeicosatrienoic acids (EETs) are potent endogenous analgesic metabolites produced from arachidonic acid by cytochrome P450s (P450s). Metabolism of EETs by soluble epoxide hydrolase (sEH) reduces their activity, while their stabilization by sEH inhibition decreases both inflammatory and neuropathic pain. Here, we tested the complementary hypothesis that increasing the level of EETs through induction of P450s by omeprazole (OME), can influence pain related signaling by itself, and potentiate the anti-hyperalgesic effect of sEH inhibitor. Rats were treated with OME (100 mg/kg/day, p.o., 7 days), sEH inhibitor TPPU (3 mg/kg/day, p.o.) and OME (100 mg/kg/day, p.o., 7 days) + TPPU (3 mg/kg/day, p.o., last 3 days of OME dose) dissolved in vehicle PEG400, and their effect on hyperalgesia (increased sensitivity to pain) induced by PGE{sub 2} was monitored. While OME treatment by itself exhibited variable effects on PGE{sub 2} induced hyperalgesia, it strongly potentiated the effect of TPPU in the same assay. The significant decrease in pain with OME + TPPU treatment correlated with the increased levels of EETs in plasma and increased activities of P450 1A1 and P450 1A2 in liver microsomes. The results show that reducing catabolism of EETs with a sEH inhibitor yielded a stronger analgesic effect than increasing generation of EETs by OME, and combination of both yielded the strongest pain reducing effect under the condition of this study. - Highlights: • The soluble epoxide hydrolase (sEH) inhibitor TPPU is anti-hyperalgesic. • Omeprazole potentiates the anti-hyperalgesic actions of TPPU. • This potentiation is associated with increased P450 activity. • The potentiation is associated with an increase in fatty acid epoxide/diol ratio. • Joint use of sEH inhibitors and P450 inducers could result in drug–drug interactions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Acoustic detection of cracks in the anvil of a large-volume cubic high-pressure apparatus

A large-volume cubic high-pressure apparatus with three pairs of tungsten carbide anvils is the most popular device for synthetic diamond production. Currently, the consumption of anvils is one of the important costs for the diamond production industry. If one of the anvils is fractured during the production process, the other five anvils in the apparatus may be endangered as a result of a sudden loss of pressure. It is of critical importance to detect and replace cracked anvils before they fracture for reduction of the cost of diamond production and safety. An acoustic detection method is studied in this paper. Two new features, nested power spectrum centroid and modified power spectrum variance, are proposed and combined with linear prediction coefficients to construct a feature vector. A support vector machine model is trained for classification. A sliding time window is proposed for decision-level information fusion. The experiments and analysis show that the recognition rate of anvil cracks is 95%, while the false-alarm rate is as low as 5.8 × 10{sup −4} during a time window; this false-alarm rate indicates that at most one false alarm occurs every 2 months at a confidence level of 90%. An instrument to monitor anvil cracking was designed based on a digital signal processor and has been running for more than eight months in a diamond production field. In this time, two anvil-crack incidents occurred and were detected by the instrument correctly. In addition, no false alarms occurred.

42 ENGINEERING↗