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Pedestrian detection is a critical task for safety-critical systems, but detecting pedestrians is challenging in low-light and adverse weather conditions. Thermal images can be used to improve robustness by providing complementary information to RGB images. Previous studies have shown that multi-modal feature fusion using convolution operation can be effective, but such methods rely solely on local feature correlations, which can degrade the performance capabilities. To address this issue, we propose an attention-based novel fusion network, referred to as INSANet (INtra-INter Spectral Attention Network), that captures global intra- and inter-information. It consists of intra- and inter-spectral attention blocks that allow the model to learn mutual spectral relationships. Additionally, we identified an imbalance in the multispectral dataset caused by several factors and designed an augmentation strategy that mitigates concentrated distributions and enables the model to learn the diverse locations of pedestrians. Extensive experiments demonstrate the effectiveness of the proposed methods, which achieve state-of-the-art performance on the KAIST dataset and LLVIP dataset. Finally, we conduct a regional performance evaluation to demonstrate the effectiveness of our proposed network in various regions. [ABSTRACT FROM AUTHOR]

In this paper, multispectral pedestrian detection is mainly discussed, which can contribute to assigning human-aware properties to automated forklifts to prevent accidents, such as collisions, at an early stage. Since there was no multispectral pedestrian detection dataset in an intralogistics domain, we collected a dataset; the dataset employs a method that aligns image pairs with different domains, i.e. RGB and thermal, without the use of a cumbersome device such as a beam splitter, but rather by exploiting the disparity between RGB sensors and camera geometry. In addition, we propose a multispectral pedestrian detector called SSD 2.5D that can not only detect pedestrians but also estimate the distance between an automated forklift and workers. In extensive experiments, the performance of detection and centroid localization is validated with respect to evaluation metrics used in the driving car domain but with distinct categories, such as hazardous zone and warning zone, to make it more applicable to the intralogistics domain. [ABSTRACT FROM AUTHOR]

• Vertical downward condensation plate heat exchanger. • Electrochemical etching generates microscale roughness. • Enhance thermal-hydraulic performance of plate heat exchanger. • Analyze effect of heat flux, mass flux, vapor quality and surface roughness on heat transfer. • Multi-objective generic algorithm optimized designed roughness. • Pareto front solutions for maximizing performance. This research employed electrochemical etching to generate microscale roughness on a plate heat exchanger (PHE) thereby enhancing condensation heat transfer in a vertical downward flow. The effects of the mass flux, vapor quality, heat flux, saturation temperature and microscale surface roughness on the condensation heat transfer coefficient (HTC) and frictional pressure drop (FPD) of R-513a flowing through a PHE was experimentally investigated. Experimental measurements were made under various heat fluxes of 5–15 kW/m2, mass fluxes of 60–80 kg/m2s, saturation temperatures of 40–50 °C, and mean vapor qualities of 0.1–0.7. HTC increased by up to 28, 26, 74, and 32.5 % as the heat flux, mass flux, average quality, and microscale surface roughness were respectively increased, but decreased by 19 % with the saturation temperature. FPD increased as the mass flux and average vapor quality increased, whereas it was reduced as the refrigerant saturation temperature increased. In contrast, the heat flux had little to no influence on FPD. Correlations for predicting the Nusselt number and friction factor were postulated by considering influential dimensionless numbers during heat transfer. Maximizing the Nusselt number and thermal performance factor was ultimately resolved using a multi-objective genetic algorithm to find a Pareto front solution. Consequently, the optimal surface roughness was found to be 9.94 μm. [ABSTRACT FROM AUTHOR]

A hydrophobic surface promotes bubble nucleation due to hydrophobicity. Thus, a hydrophobic surface has a higher boiling heat transfer coefficient (BHTC) than a hydrophilic surface. In contrast, a hydrophilic surface supplies liquid to a heating surface. This mechanism enhances the critical heat flux (CHF). In this respect, there is a trade-off between a hydrophobic and a hydrophilic surface. In this study, we examined the effect of heterogeneous wetting surfaces on flow boiling performance. We designed four types of hydrophobic stripes; there are two directions, parallel and crossed to the flow, and the width (the pitch) of the hydrophobic stripes in each direction is 3 or 1 mm. In the macro-channel, the flow boiling performance on the surfaces depended on the patterns. The parallel striped surfaces had higher CHFs than the crossed striped surfaces. In addition, the narrow patterns in each direction had higher CHFs than the wide patterns. The difference in BHTC among the parallel striped surfaces was not large, but the difference in BHTC among the crossed striped surfaces was considerable. A visualization technique revealed that the merging and confinement of bubbles were key factors in explaining the boiling characteristics. Considering the drag coefficient and bubble breakup, we suggest appropriate designs of the hydrophobic pattern for the improvement of BHTC and CHF in the flow boiling performance. [ABSTRACT FROM AUTHOR]

A smart surface that is a TiO 2 -coated surface (TCS) is a hydrophobic surface initially, but becomes a hydrophilic surface when heated. Therefore, such a surface can be used to enhance both boiling heat transfer (BHT) and critical heat flux (CHF) in pool boiling. In the present study, the time effect of the wetting transition of TCS was focused on. The CHF on TCS was enhanced more when the holding time of the heat flux in high-temperature regime was increased. By observing changes in contact angles on TCS through heat treatment in air, it was found that the wetting transition was affected not only by the temperature, but also by the time. Thus, a variation of the receding contact angle was correlated in the form of an exponential function. The suggested empirical correlation includes temperature and time, and it describes the transition of the receding contact angle. The correlation was also used to predict the CHF on TCS in pool boiling. As a result, CHFs on TCS could be explained using the correlation. [ABSTRACT FROM AUTHOR]

Modified surfaces with graphene coatings were evaluated experimentally to enhance nucleate boiling performance on an orientated surface, from upward to downward (0°, 45°, 90°, 120°, 135°, 150°, 160°, and 170°). Two-dimensional (2D) laminate and three-dimensional (3D) porous graphene were prepared for surface modification, and their boiling heat transfer coefficient (BHTC) and critical heat flux (CHF) values were evaluated according to orientation angle. Moreover, their boiling structures were observed and analyzed using high-speed visualization. The results showed that the surfaces coated with 2D and 3D graphene had enhanced BHTC and CHF performance in comparison with the bare surface with no graphene modification. The 2D graphene surface showed increased nucleate site density and early onset of nucleate boiling, resulting in enhanced BHTC, by 40%, in the downward condition. The enhancement ratio of CHF was 40% on 2D graphene and 20–25% on 3D graphene. [ABSTRACT FROM AUTHOR]

We report nucleate pool boiling experiments using reduced graphene oxide (RGO) colloidal suspensions on a silicon dioxide plate surface, in order to describe a kind of quasi-transition boiling phenomenon, whereby the wall temperature gradually increased as a function of time without a rapid increase in temperature at the critical heat flux (CHF). Under boiling conditions, the RGO flakes formed a three-dimensional (3D) graphene structure at the surface, so that the RGO colloidal suspension exhibited a larger boiling heat transfer coefficient and larger CHF with the quasi-transition boiling phenomenon than when the working fluid was deionized water. To evaluate the effect of the heat flux conditions on the phenomenon, various heat fluxes were investigated, and the transient behavior of the boiling heat transfer characteristics was observed. We found that the rate of change of the wall temperature in the quasi-transition boiling regime was proportional to the heat flux, even if the higher heat flux was applied following the onset of the increase in the wall temperature. [ABSTRACT FROM AUTHOR]

Abstract: An investigation into the water discharge characteristics of proton exchange membrane (PEM) fuel cells is carried out by using a feasibility test apparatus and the Neutron Radiography Facility (NRF) at HANARO. The feasibility test apparatus was composed of a distilled water supply line, a compressed air supply line, heating systems, and single PEM fuel cells, which were a 1-parallel serpentine type with a 100cm2 active area. Three kinds of methods were used: compressed air supply-only; heating-only; and a combination of the methods of a compressed air supply and heating, respectively. The resultant water discharge characteristics are different according to the applied methods. The compressed air supply only is suitable for removing the water at a flow field and a heating only is suitable for water at the MEA. Therefore, in order to remove all the water at PEM fuel cells, the combination method is needed at the moment. [Copyright &y& Elsevier]

Abstract: In this investigation, we prepared a 3-parallel serpentine single PEMFC which has an active area of 25cm2 and a flow channel cross section of 1×1mm. Distribution and transport of water in an operating PEMFC were observed by varying the flow directions (co-current and counter-current) in each channel and the differential pressures (100, 200, 300kPa) applied between the anode and cathode channels. This investigation was performed at the neutron imaging facility at the NIST of which the collimation ratio and neutron fluence rate are 600, 7.2×106 n/s/cm2, respectively. Neutron image was continuously recorded by an amorphous silicon flat panel detector every 1s during the operation of the fuel cell. It has been observed that the differential pressure affects the total amount of water produced while the flow direction affects the spatial distribution of water when the neutron images were analyzed for several different operating conditions. More specifically, the amount of water production in the fuel cell increased as the partial pressure increases at a given current density and the water production was more uniform for the counter current than the co-current case. It is shown that the neutron imaging technique is a powerful tool to visualize the PEMFC. The information on the water distribution and behavior at an operating PEMFC helps improve the efficiency of PEMFC. [Copyright &y& Elsevier]

Lithium-ion batteries are widely used in electric vehicles because of their high capacity and voltage. However, some drawbacks to the battery stability exist. The aim of our research was to determine the optimum width and number of channels of a cold plate. To estimate the temperature distribution and heat transfer rate, the MSMD (multi-scale multi-dimensional) - Newman P2D model in ANSYS Fluent was used. Prior to comparing the heat transfer rates of the various battery surfaces using different cold plates, the surface temperature of the battery (LiFePO4) at discharge rates of 2C, 3C, and 4C was calculated to determine the battery characteristics. Subsequently, two cold plates were attached to both sides (front and back) of the batteries and the heat transfer rate of the battery surface in contact with the cold plate, and the pressure drop between the inlet and outlet of the channels during the discharge process were estimated. In addition, the j and f factors, which are used to estimate the cooling performance of the cold plates, were calculated. In determining the most efficient cold plate options, the trade-off between the heat transfer coefficient and the pressure drop is also important for the relationship between the two factors (j and f factors). [ABSTRACT FROM AUTHOR]

Abstracts An experimental study was carried out to measure the boiling heat transfer and critical heat flux on serpentine-pattern thin film heater having a 120 nm thick platinum under pool boiling. Pool boiling critical heat flux experiments were performed using plain heater, 2-serpentine, 4-serpentine, and 6-serpentine pattern thin film heater. From the experimental results, it is found that the measured boiling heat transfer performance and critical heat flux are dependent of serpentine pattern, however critical heat flux is independent of the number of serpentine pattern. Measured data of critical heat flux are compared with classical model of critical heat flux, and degradation phenomena of boiling heat transfer and critical heat flux on serpentine-pattern thin film heater under pool boiling analyzed in this work. [ABSTRACT FROM AUTHOR]

Abstract: The primary role of the gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFC) is to maintain the delicate balance between water retention and removal in GDLs. Water management in the fuel cell is related to the breakthrough pressure at which water starts to pass through GDL, and the drainage pressure, which is maintained after the breakthrough. These pressures are both related to water management in fuel cells. Here we measured these pressures for two different GDLs and used X-ray tomography to visualize the water distributions within them. We then relate the variations in liquid pressures to the visualization and discuss water management in PEMFC. [Copyright &y& Elsevier]

Abstract: This report provides a preliminary insight into the benefits and effectiveness of neutron radiography in identifying alien materials, namely shot balls hidden in a turbine blade that are otherwise undetected using other methods. The detection of 0.2-mm-diameter shot balls in gas-cooled turbine blades is possible for thermal neutron radiography. A tagging processing is more useful for a distinctive image of newer turbine blades. Areas of concern for the tagging process include the solution concentration and the possibility of a slight washing of the blades. The location of the shot balls within the turbine blades tagged with Gd((2%, 5%)+water) was shown. Shot balls were placed externally on a turbine blade (F100-700, F100-200) surface in order to check for a dead zone from a surface examination. The image is produced from neutron radiography after a 5min exposure time. When the blade is tagged with 2% and 5% Gd with slight washing, the shot can also be effectively seen on the SR-45 film. Shot balls are more obvious on a neutron image SR-45 film than an image plate or a DR film. [Copyright &y& Elsevier]

• Experimental investigation of air natural convection in a turning L-shape channel. • Vertical/horizontal gaps as experimental parameters and varying heat load conditions. • Critical parameter of cooling performance/thermal behavior estimated from measured wall/air temperatures. • Transition phenomenon eliminating the entrance effect near the mid-height of the vertical channel. • Cooling performance enhanced by minimizing the entrance effect as recognized from air temperature profiles. The geometrical effect of natural convection in an air channel with a cavity at the turning section was investigated experimentally by controlling the vertical upper gap (G, 100–75 mm) and horizontal lower channel gap (B, 100 - 300 mm) and varying the heat load conditions (P, 1.35–6.20 kW). The thermal behavior in the channel was considered in terms of the temperature distributions of the walls, and the air temperature field was estimated from the measured air temperature. Additionally, the heat removal performance was analyzed for changes in each parameter to find the critical design parameter on cooling performance. The heat load condition positively affected the heat removal performance, but it did not affect the trend of the wall temperature distributions or the shape of the temperature field in the channel. A lower channel gap directly affected the cooling in the lower channel (cavity) between the lower curved wall and bottom but did not appreciably affect the cooling in the upper vertical channel between both vertical walls and overall heat removal performance (RSD Max = 3.2 %). As a result, the most critical parameter was the upper vertical channel gap because it affected both lower and upper channels and played a vital role in determining the overall heat transfer performance (RSD Max = 11.0 %). Additionally, it was confirmed that the location where the peak wall temperature appeared changed as the vertical gap size was altered. Interestingly, we found that the transition phenomenon eliminating the entrance effect occurred above the mid-height of the vertical channel in all experimental cases, and it was directly related to the heat removal performance. The temperature profiles developed smoothly along the height in only the G175 cases, which were the maximum heat removal performance cases, owing to the minimized entrance effect in the channel. In contrast, the temperature profiles below the mid-height of the vertical channel changed rapidly due to the entrance effect in other cases. [ABSTRACT FROM AUTHOR]

The graphene has been interested world-widely for the superb mechanical and electrical properties. Among them, the thermal conductivity of graphene was often reported as the 500–5000 W/mK. We tried to apply the graphene to the thermal application of boiling heat transfer through the graphene coating. The graphene was used for the reduced graphene oxide flakes in water (RGO colloid). The RGO colloid boiling on silicon-dioxide heater (substrate) showed both the boiling heat transfer and the critical heat flux enhancement as 65% and 70%, respectively. After RGO colloid boiling, the base graphene layer (BGL) with 10–100 nm thickness below the self-assembled foam-like graphene (SFG) was observed. In order to confirm the effect of BGL on the enhanced boiling performance, the only water boiling on an artificial graphene multilayers (RGO film) coated heater was conducted, and shows the similar result with the RGO colloid boiling. [ABSTRACT FROM AUTHOR]

Sap water is distributed and utilized through xylem conduits, which are vascular networks of inert pipes important for plant survival. Interestingly, plants can actively regulate water transport using ion-mediated responses and adapt to environmental changes. However, ionic effects on active water transport in vascular plants remain unclear. In this report, the interactive ionic effects on sap transport were systematically investigated for the first time by visualizing the uptake process of ionic solutions of different ion compositions (K+/Ca2+) using synchrotron X-ray and neutron imaging techniques. Ionic solutions with lower K+/Ca2+ ratios induced an increased sap flow rate in stems of Olea europaea L. and Laurus nobilis L. The different ascent rates of ionic solutions depending on K+/Ca2+ ratios at a fixed total concentration increases our understanding of ion-responsiveness in plants from a physicochemical standpoint. Based on these results, effective structural changes in the pit membrane were observed using varying ionic ratios of K+/Ca2+. The formation of electrostatically induced hydrodynamic layers and the ion-responsiveness of hydrogel structures based on Hofmeister series increase our understanding of the mechanism of ion-mediated sap flow control in plants. [ABSTRACT FROM AUTHOR]

The fabrication of gratings including metal deposition processes for highly neutron absorbing lines is a critical issue to achieve a good visibility of the grating-based phase imaging system. The source grating for a neutron Talbot-Lau interferometer is an array of Gadolinium (Gd) structures that are generally made by sputtering, photo-lithography, and chemical wet etching. However, it is very challenging to fabricate a Gd structure with sufficient neutron attenuation of approximately more than 20 μm using a conventional metal deposition method because of the slow Gd deposition rate, film stress, high material cost, and so on. In this article, we fabricated the source gratings for neutron Talbot-Lau interferometers by filling the silicon structure with Gadox particles. The new fabrication method allowed us a very stable and efficient way to achieve a much higher Gadox filled structure than a Gd film structure, and is even more suitable for thermal polychromatic neutrons, which are more difficult to stop than cold neutrons. The newly fabricated source gratings were tested at the polychromatic thermal neutron grating interferometer system of HANARO at the Korea Atomic Energy Research Institute, and the visibilities and images from the neutron phase imaging system with the new source gratings were compared with those fabricated by a Gd deposition method. [ABSTRACT FROM AUTHOR]

Abstract: X-ray imaging detectors in combination with scintillator screens have been widely used in digital X-ray imaging applications. Gd2O2S:Tb was used as scintillation material for pixelated scintillator screens based on silicon substrates (wafer) with a micropore array of various dimensions fabricated using the photolithography and deep reactive ion etching (DRIE) process. The relative light output and the modulation transfer function (MTF) of each fabricated scintillator screen were measured by a cooled CCD and compared with those of Lanex screens. The spatial resolution of our scintillator screens was higher but their light outputs were lower than those of Lanex screen probably due to the loss of light at the wall surfaces. Therefore further treatment of the wall surface, such as reflective coating, seems necessary to compensate the light loss. [Copyright &y& Elsevier]