We present a method named NPFimg, which automatically identifies multivariate chemo-/biomarker features of analytes in chromatography–mass spectrometry (MS) data by combining image processing and ...machine learning. NPFimg processes a two-dimensional MS map (m/z vs retention time) to discriminate analytes and identify and visualize the marker features. Our approach allows us to comprehensively characterize the signals in MS data without the conventional peak picking process, which suffers from false peak detections. The feasibility of marker identification is successfully demonstrated in case studies of aroma odor and human breath on gas chromatography–mass spectrometry (GC–MS) even at the parts per billion level. Comparison with the widely used XCMS shows the excellent reliability of NPFimg, in that it has lower error rates of signal acquisition and marker identification. In addition, we show the potential applicability of NPFimg to the untargeted metabolomics of human breath. While this study shows the limited applications, NPFimg is potentially applicable to data processing in diverse metabolomics/chemometrics using GC–MS and liquid chromatography–MS. NPFimg is available as open source on GitHub (http://github.com/poomcj/NPFimg) under the MIT license.
► Proposing heat transfer models suitable to heat exchangers in diaphragm wall. ► Developing a design method of heat exchangers in diaphragm wall. ► Verifying the proposed models with numerical ...solution and field measured data.
The technology of embedding heat exchange tubes in diaphragm walls is a new direction for Ground-coupled Heat Pumps (GCHP). This paper examines the heat transfer model and design method for geothermal heat exchangers in diaphragm walls, which are seldom investigated in the world. Two-dimensional (2D) heat transfer models for diaphragm wall heat exchangers (DWHE) are established. A design method for DWHE is further developed to calculate the hourly heat exchange capacity of DWHE and to get the reasonable design parameter of DWHE. The DWHE model over the excavation line has the same changing trend with numerical solutions, and the relative errors between them are less than 2%. The relative errors of calculated heat exchange rate per meter using DWHE model and measured data are less than 6% after running 10h. The relative errors of temperature between DWHE model under the excavation line and the measured data at different positions are no more than 9%, whereas the relative error between the tradition models in GCHP (line source model and finite-line source model) and the measured data may reach as much as 40%.
In order to solve the freezing damage problem of tunnel in a cold region, an innovative tunnel lining ground heat exchangers (GHEs) heating system was introduced in China for the first time and ...applied to Linchang tunnel in Inner Mongolia. This new-type system utilized the tunnel linings as heat exchanger to extract geothermal energy from the surrounding rock in the middle part of the tunnel so as to heat tunnel lining and the drainage system at the tunnel entrance. As for the thermal analysis and design of it, the classical line heat source model and “hollow” cylindrical heat source model for borehole GHEs are not applicable. Therefore, a new line source model was put forward in this paper, which considered both composite medium and time-dependent boundary conditions. Its analytical solution was obtained using the superposition principle and finite integral transfer method. The calculated results from the new model were validated by the experimental data of thermal response tests. Furthermore, the new model was applied to analyze the impact factors of heat transfer performance for design optimization, including the ground temperature as well as the flow rate and the inlet temperature of heat carrier liquid. It was proven that the new model can provide adequate tools for the design of tunnel lining GHE heating system.
► An innovative technology, tunnel lining GHEs was introduced for the first time. ► A new line source model of tunnel lining GHEs was put forward in this paper, ► The calculated results were validated by the experimental data. ► The new model was applied to analyze the impact factors of heat transfer performance.
Surface molecular transformations on nanoscale metal oxides are inherently complex, and directing those reaction pathways is still challenging but important for designing their various applications, ...including molecular sensing, catalysts, and others. Here, a rational strategy to direct a reaction pathway of volatile carbonyl compounds (nonanal: biomarker) on single-crystalline ZnO nanowire surfaces via molecular modification is demonstrated. The introduction of a methylphosphonic acid modification on the ZnO nanowire surface significantly alters the surface reaction pathway of nonanal via suppressing the detrimental aldol condensation reaction. This is directed by intentionally decreasing the probability of two neighboring molecular activations on the nanowire surface. Spectrometric measurements reveal the correlation between the suppression of the aldol condensation surface reaction and the improvement in the sensor performance. This tailored surface reaction pathway effectively reduces the operating temperature from 200 to 100 °C while maintaining the sensitivity. This is because the aldol condensation product ((E)-2-heptyl-2-undecenal) requires a higher temperature to desorb from the surface. Thus, the proposed facile strategy offers an interesting approach not only for the rational design of metal oxide sensors for numerous volatile carbonyl compounds but also for tailoring various surface reaction pathways on complex nanoscale metal oxides.
A silver-catalyzed three-component reaction involving alkynes, Selectfluor
, and diethyl phosphite was employed for the one-pot formation of C(sp
)-F and C(sp
)-P bonds to provide an efficient access ...to β-fluorovinylphosphonates in a highly regio- and stereoselective manner under mild reaction conditions. This reaction is operationally simple and offers an excellent functional group tolerance as well as a broad substrate scope that includes both terminal and internal alkynes. The reaction proceeded through the oxidative generation of a P-centered radical and subsequent fluorine atom transfer.
The emergence of curved shield tunnels poses a significant construction challenge. If the quality of the segment assembly is not guaranteed, many segment cracks and damage will result from the stress ...concentration. Sensing the contact stresses between segmental joints is necessary to improve the quality of segments assembled for shield tunnel construction. Polyvinylidene difluoride (PVDF) piezoelectric material was chosen for the sensor because it can convert contact stresses into electrical signals, allowing the state of the segmental joints to be effectively sensed. It matches the working environment between the segmental joints of the shield tunnel, where flexible structures such as rubber gaskets and force transfer pads are present. This study proposes a piezoelectric sensing method for segmental joints in shield tunnels and conducts laboratory tests, numerical analyses, and field tests to validate the feasibility of the method. The results indicate that the PVDF film sensor can effectively sense the entire compression process of the gasket with different amounts of compression. The piezoelectric cable sensor can effectively sense the joint offset direction of the gasket. For differently shaped sections, the variation in the force sensed by the piezoelectric cable sensors was different, as verified by numerical simulation. Through the field test, it was found that the average contact stress between the segmental joints was in the range of 1.2–1.8 MPa during construction of the curved shield tunnels. The location of the segmental joints and the type of segment affect the contact stress value. The field monitoring results show that piezoelectric sensing technology can be successfully applied during assembly of the segments for effective sensing of the contact stress.
A PtCl2-catalyzed 3,3-rearrangement/3+2-cycloaddition of propargylic 3-indoleacetates is developed. Besides the efficient formation of highly functionalized tetracyclic cyclopentenes, the reaction is ...dramatically divergent from that catalyzed by cationic AuI. Moreover, the synthetic potential of this method is demonstrated by a succinct synthesis of the tetracyclic core of vindolinine.
We demonstrate the facile, rational synthesis of monodispersedly sized zinc oxide (ZnO) nanowires from randomly sized seeds by hydrothermal growth. Uniformly shaped nanowire tips constructed in ...ammonia-dominated alkaline conditions serve as a foundation for the subsequent formation of the monodisperse nanowires. By precisely controlling the sharp tip formation and the nucleation, our method substantially narrows the distribution of ZnO nanowire diameters from σ = 13.5 nm down to σ = 1.3 nm and controls their diameter by a completely bottom-up method, even initiating from randomly sized seeds. The proposed concept of sharp tip based monodisperse nanowires growth can be applied to the growth of diverse metal oxide nanowires and thus paves the way for bottom-up grown metal oxide nanowires-integrated nanodevices with a reliable performance.
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