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Design of Thermophysical Properties Test System by Laser Point Heat Source Method
摘要： Laser is widely used in material thermophysical properties testing because of its good test accuracy and test efficiency. However, due to the high market price of laser flash devices, their promotion space is limited. Based on the unsteady heat transfer model of a laser point heat source, the enantiomorphous heat source theory was introduced to modify the influence of an adiabatic boundary on the temperature rise of a measuring point. The thermal conductivity and thermal diffusivity of isotropic materials were calculated by numerical analysis combined with computer programming. A thermophysical property test system was developed, and the thermophysical properties of blast furnace firebrick, marble, and diatomite brick were studied. The results showed that the maximum repeatable accuracy error was 4.75%, and the maximum relative deviation from the reference value was 2.04%. The effective test range of the device was that the thermal conductivity was less than 3 W∕(m ? K). Compared with the laser flash method, the device does not require high test-time accuracy and data collection instantaneity in terms of test principles. Therefore, the device can use a general-level laser generator, temperature sensor, timer, data collector, and so on, and the hardware cost is greatly reduced.
关键词： thermophysical properties,thermal diffusivity,test system,thermal conductivity,laser point heat source
更新于2025-09-23 15:19:57
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Manipulation of Biomolecules Into Nanogap by Plasmonic Optical Excitation for Highly Sensitive Biosensing
摘要： This paper presents an apparatus and methodology for an advanced accelerated power cycling test of insulated-gate bipolar transistor (IGBT) modules. In this test, the accelerated power cycling test can be performed under more realistic electrical operating conditions with online wear-out monitoring of tested power IGBT module. The various realistic electrical operating conditions close to real three-phase converter applications can be achieved by the simple control method. Further, by the proposed concept of applying the temperature stress, it is possible to apply various magnitudes of temperature swing in a short cycle period and to change the temperature cycle period easily. Thanks to a short temperature cycle period, test results can be obtained in a reasonable test time. A detailed explanation of apparatus such as configuration and control methods for the different functions of accelerated power cycling test setup is given. Then, an improved in situ junction temperature estimation method using on-state collector–emitter voltage VC E O N and load current is proposed. In addition, a procedure of advanced accelerated power cycling test and test results with 600 V, 30 A transfer molded IGBT modules are presented in order to verify the validity and effectiveness of the proposed apparatus and methodology. Finally, physics-of-failure analysis of tested IGBT modules is provided.
关键词： insulated-gate bipolar transistor module,physics-of-failure,power cycling test,lifetime model,Failure mechanism,reliability
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) - Macau, China (2019.11.3-2019.11.8)] 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) - Free-Space Features: Global Localization in 2D Laser SLAM Using Distance Function Maps
摘要： A method for selecting a graphical model -vector-valued stationary Gaussian time series was recently proposed by Matsuda and uses the Kullback–Leibler divergence measure to define a test statistic. This statistic was used in a backward selection procedure, but the algorithm is prohibitively expensive for large . A high degree of sparsity is not assumed. We show that reformulation in terms of a multiple hypothesis test and simulations support the reduces computation time by the assertion that power levels are attained at least as good as those achieved by Matsuda’s much slower approach. Moreover, the new scheme is readily parallelizable for even greater speed gains.
关键词： multiple hypothesis test,Kullback–Leibler divergence,vector-valued time series,Undirected graph
更新于2025-09-23 15:19:57
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The Supplementary Motor Area Responsible for Word Retrieval Decline After Acute Thalamic Stroke Revealed by Coupled SPECT and Near-Infrared Spectroscopy
摘要： Damage to the thalamus may affect cognition and language, but the underlying mechanism remains unknown. In particular, it remains a riddle why thalamic aphasia occasionally occurs and then mostly recovers to some degree. To explore the mechanism of the affected cognition and language, we used two neuroimaging techniques—single-photon emission computed tomography (SPECT), suitable for viewing the affected brain distribution after acute thalamic stroke, and functional near-infrared spectroscopy (f-NIRS), focusing on hemodynamic responses of the supplementary motor area (SMA) responsible for speech production in conjunction with the frontal aslant tract (FAT) pathway. SPECT yielded common perfusion abnormalities not only in the fronto–parieto–cerebellar loop, but also in the SMA, IFG and surrounding language-relevant regions. In NIRS sessions during a phonemic verbal fluency task, we found significant word retrieval decline in acute thalamic patients relative to age-matched healthy volunteers. Further, NIRS showed strong correlation between word retrieval and posterior SMA responses. In addition, follow-up NIRS exhibited increased bilateral SMA responses linked to improving word retrieval ability. The findings suggest that cognitive dysfunction may be related to the fronto–parieto–cerebellar loop, while language dysfunction is attributed to the SMA, IFG and language-related brain areas. SMA may contribute to the recovery of word retrieval difficulty and aphasia after thalamic stroke.
关键词： SPECT,hemodynamic response,perfusion,verbal fluency test,thalamic aphasia,FAT: frontal aslant tract,cerebro-cerebellar diaschisis,functional near-infrared spectroscopy (f-NIRS)
更新于2025-09-23 15:19:57
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Concrete Crack Monitoring Using a Novel Strain Transfer Model for Distributed Fiber Optics Sensors
摘要： In this paper, we study the strain transfer mechanism between a host material and an optical fiber. A new analytical model handling imperfect bonding between layers is proposed. A general expression of the crack-induced strain transfer from fractured concrete material to optical fiber is established in the case of a multilayer system. This new strain transfer model is examined through performing wedge splitting tests on concrete specimens instrumented with embedded and surface-mounted fiber optic cables. The experimental results showed the validity of the crack-induced strain expression fitted to the distributed strains measured using an Optical Backscattering Reflectometry (OBR) system. As a result, precise estimations of the crack openings next to the optical cable location were achieved, as well as the monitoring of the optical cable response through following the strain lag parameter.
关键词： crack,distributed strains,crack opening,wedge splitting test,fiber optics sensors,strain transfer,imperfect bonding,concrete
更新于2025-09-23 15:19:57
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Multiple epitaxial lift-off of stacked GaAs solar cells for low-cost photovoltaic applications
摘要： This paper presents a multilayer peeling from a stacked cell structure as an approach for the cost reduction of III–V solar cells. We demonstrate the separation of two-layer stacked GaAs solar cells with Al(Ga)As release layers on the GaAs substrate into individual layers without cracks. The cells in each layer peeled from the stacked structure show equivalent device performances. Thermal cycling tests with repeated heating to 85 °C and cooling to ?40 °C show that the flexible GaAs thin-film cell exhibits a high durability against temperature changes. Further, a damp heat test conducted at 85 °C and 85% humidity indicates that the cell has long-term stability. These results suggest that the flexible GaAs thin-film cells fabricated by peeling from stacked structures have a high reliability and prove that the separation of the stacked cell structures into individual layers is effective in fabricating low-cost III–V solar cells.
关键词： epitaxial lift-off,cost reduction,damp heat test,photovoltaic applications,thermal cycling,GaAs solar cells
更新于2025-09-23 15:19:57
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The International Round Robin Test of Magnetostriction Measurement of Grain-oriented Electrical Steel by Means of a Single Sheet Tester and an Optical Sensor
摘要： This paper reports the results of the round robin test (hereafter RRT) of magnetostriction measurement using the test apparatus following IEC 60404-17 from April 2019 to August 2019. The main purpose of the RRT is to identify factors affecting the magnetostriction measurement, and then to estimate the reproducibility of the measurements. Nine anonymous laboratories, whose test apparatuses are a little different from the draft standard, participated in the RRT. In the progress of the RRT, we identified factors affecting the magnetostriction measurement. Finally, the reproducibility of the measurements was estimated. Doshisha Univ. acts as the reference laboratory.
关键词： Single Sheet Tester,Optical Sensor,Magnetostriction,Grain-oriented Electrical Steel,Round Robin Test
更新于2025-09-23 15:19:57
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nAdaptive detection of point-like targets based on a reduced-dimensional data model
摘要： This paper approaches the problem of detecting a point-like target in Gaussian background. The useful signal lies in an one-dimensional subspace spanned by a known steering vector. The Gaussian disturbance fills the whole observation space. Since the disturbance outside the signal subspace is unrelated to the decision result, it is eliminated by pre-multiplying the recorded data by the conjugate transpose of the steering vector in this paper. This preprocessing is not applied in the classical detectors, such as the generalized likelihood ratio test (GLRT), the adaptive matched filter (AMF), etc. This preprocessing results in a new scalar data model where the useful signal and disturbance lie in the same space. Based on this scalar data model, two new detectors are designed through the one-step and two-step GLRT, respectively. Their probabilities of false alarms and detections are derived analytically. The one- (two-) step GLRT-based detector has the (approximately) constant false alarm rate feature in the Gaussian background. Simulation results show that the proposed detectors outperform those classical ones when finite training data is available. The one-step GLRT-based detector is more robust to mismatched signals than those classical detectors.
关键词： generalized likelihood ratio test,Adaptive detection,constant false alarm ratio,homogeneous environment,point-like target
更新于2025-09-23 15:19:57
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Distributed Thermal Response Tests Using a Heating Cable and Fiber Optic Temperature Sensing
摘要： Thermal response tests are used to assess the subsurface thermal conductivity to design ground-coupled heat pump systems. Conventional tests are cumbersome and require a source of high power to heat water circulating in a pilot ground heat exchanger. An alternative test method using heating cable was verified in the field as an option to conduct this heat injection experiment with a low power source and a compact equipment. Two thermal response tests using heating cable sections and a continuous heating cable were performed in two experimental heat exchangers on different sites in Canada and France. The temperature evolution during the tests was monitored using submersible sensors and fiber optic distributed temperature sensing. Free convection that can occur in the pipe of the heat exchanger was evaluated using the Rayleigh number stability criterion. The finite and infinite line source equations were used to reproduce temperature variations along the heating cable sections and continuous heating cable, respectively. The thermal conductivity profile of each site was inferred and the uncertainly of the test was evaluated. A mean thermal conductivity 15% higher than that revealed with the conventional test was estimated with heating cable sections. The thermal conductivity evaluated using the continuous heating cable corresponds to the value estimated during the conventional test. The average uncertainly associated with the heating cable section test was 15.18%, while an uncertainty of 2.14% was estimated for the test with the continuous heating cable. According to the Rayleigh number stability criterion, significant free convection can occur during the heat injection period when heating cable sections are used. The continuous heating cable with a low power source is a promising method to perform thermal response tests and further tests could be carried out in deep boreholes to verify its applicability.
关键词： fiber optic,geothermal,heating cable,thermal response test,thermal conductivity
更新于2025-09-19 17:15:36
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Comparative study on stability of boron doped diamond coated titanium and niobium electrodes
摘要： The service life of boron doped diamond (BDD) coated electrodes is closely related to the substrate material and preparation process of the BDD coatings. In this paper, the failure process of BDD coated titanium (Ti/BDD) and niobium (Nb/BDD) electrodes prepared by arc plasma chemical vapor deposition method was comparatively studied by accelerated life test. The results showed that the main failure mechanism of the two types of electrodes is delamination of the BDD coatings, accompanied by coatings’ corrosion. The delamination of BDD coatings from both the substrates showed an incubation period, with the Ti/BDD electrode having a much shorter incubation period and a higher coating delamination rate than its Nb/BDD counterpart. By comparing growth process of diamond coatings and corrosion behavior of carbides formed on both substrates, it is found that on a Ti substrate, diamond coating is more liable to incorporate pore like defects, and carbide layer formed beneath the diamond coating is more susceptible to corrosion in electrolysis solution. It is believed that these two factors would be responsible for short service life for Ti/BDD electrodes as compared with that for Nb/BDD electrodes.
关键词： BDD electrode,accelerated life test,carbide layer,failure mechanism
更新于2025-09-19 17:15:36