•H2O dissociative adsorption on the χ-Fe5C2(010) surface was investigated.•The χ-Fe5C2(010) surface has both iron and carbon regions.•Surface iron region is active for H2O dissociative adsorption and ...H2 formation.•Pre-adsorbed oxygen atoms play a significant role for further H2O adsorption.•Surface carbon region is inactive for H2O dissociative adsorption.
Spin-polarized density functional theory calculations (GGA–PBE) have been carried out to study H2O adsorption and dissociation on the Fe5C2(010) surface. It is found that the iron region on the Fe5C2(010) surface is active for H2O adsorption and dissociation, while the carbon region is inactive. For H2O adsorption in the iron region, H2O prefers the top site of the surface iron atoms, and significant hydrogen bonding interaction has been found at high H2O coverage on the basis of the computed adsorption energies and the intermolecular O–H distances. In the iron region H2O dissociation (H2O→H+OH; OH→H+O) is favored both kinetically and thermodynamically. On one O pre-covered surface, O-assisted H2O dissociation becomes favorable kinetically (O+H2O→OH+OH) and further OH dissociation (OH→H+O) becomes difficult thermodynamically. Upon the increase of surface O coverage, H2O dissociation becomes difficult, while H2 formation from the surface adsorbed H atoms becomes easy. On the potential energy surface, the dissociation of four H2O molecules into four surface O and four H2 molecules (4H2O(g)→4O(s)+4H2(g)) is still thermodynamically favorable by 0.63eV, and the iron region is fully covered by surface oxygen atoms. Thermodynamic analysis reveals clearly that the catalyst surface has always adsorbed oxygen atoms under water environment and their number in the iron region depends on temperature and water content; and high temperature and low H2O partial pressure can maintain the catalyst stability and excess H2O partial pressure will result in full oxidation. For the oxidation of one surface carbon atom, it is necessary to migrate one of the four adsorbed oxygen atoms from the iron region to the carbon region, and the H2O assisted CO2 formation is more favorable than the direct CO2 formation. The overall surface carbon oxidation, FexCy+4H2O(g)→O2FexCy–1+CO2(g)+4H2(g), is thermodynamically accessible. Detailed comparisons show that the Fe(100) and Fe5C2(010) surfaces are very similar in H2O adsorption and dissociation at low coverage.
An Accelerator for High Efficient Vision Processing Zidong Du; Shaoli Liu; Fasthuber, Robert ...
IEEE transactions on computer-aided design of integrated circuits and systems,
2017-Feb., 2017-2-00, Volume:
36, Issue:
2
Journal Article
Peer reviewed
In recent years, neural network accelerators have been shown to achieve both high energy efficiency and high performance for a broad application scope within the important category of recognition and ...mining applications. Still, both the energy efficiency and performance of such accelerators remain limited by memory accesses. In this paper, we focus on image applications, arguably the most important category among recognition and mining applications. The neural networks which are state-of-the-art for these applications are convolutional neural networks (CNNs), and they have an important property: weights are shared among many neurons, considerably reducing the neural network memory footprint. This property allows to entirely map a CNN within an SRAM, eliminating all DRAM accesses for weights. By further hoisting this accelerator next to the image sensor, it is possible to eliminate all remaining DRAM accesses, i.e., for inputs and outputs. In this paper, we propose such a CNN accelerator, placed next to a CMOS or CCD sensor. The absence of DRAM accesses combined with a careful exploitation of the specific data access patterns within CNNs allows us to design an accelerator which is highly energy-efficient. We present a single-core implementation down to the layout at 65 nm, with a modest footprint of 5.94 mm 2 and consuming only 336 mW, but still about 30× faster than high-end GPUs. For visual processing with higher resolution and frame-rate requirements, we further present a multicore implementation with elevated performance.
In order to achieve rapid detection of galactooligosaccharides (GOS), fructooligosaccharides (FOS), calcium (Ca), and vitamin C (Vc), four micronutrient components in infant formula milk powder, this ...study employed four methods, namely Standard Normal Variate (SNV), Multiplicative Scatter Correction (MSC), Normalization (Nor), and Savitzky–Golay Smoothing (SG), to preprocess the acquired original spectra of the milk powder. Then, the Competitive Adaptive Reweighted Sampling (CARS) algorithm and Random Frog (RF) algorithm were used to extract representative characteristic wavelengths. Furthermore, Partial Least Squares Regression (PLSR) and Support Vector Regression (SVR) models were established to predict the contents of GOS, FOS, Ca, and Vc in infant formula milk powder. The results indicated that after SNV preprocessing, the original spectra of GOS and FOS could effectively extract feature wavelengths using the CARS algorithm, leading to favorable predictive results through the CARS-SVR model. Similarly, after MSC preprocessing, the original spectra of Ca and Vc could efficiently extract feature wavelengths using the CARS algorithm, resulting in optimal predictive outcomes via the CARS-SVR model. This study provides insights for the realization of online nutritional component detection and optimization control in the production process of infant formula.
Network-on-Chip (NoC) is a promising replacement of bus architecture due to its better scalability. In state-of-the-art NoCs, each packet contains several fixed-length flits, which facilitates ...allocations of network resources but brings in many unused bits. In this paper, we propose a novel technique called Stealth-ACK to effectively address the above problem. Stealth-ACK leverages unused bits in head flits of non-ACK packets to carry and stealthily transmit ACK information. Such stealth transmissions of ACK information effectively reduce not only the amount of dedicated ACK packets on NoC, but also the number of unused bits in head flits of non-ACK packets, which significantly reduces wastes on NoC bandwidth. Experimental results show that Stealth-ACK averagely increases the throughput of 16 × 16 2-D mesh NoC by 11.9%, and averagely reduces the NoC latency by 34.8% on application traces of SPLASH-2. Moreover, Stealth-ACK only requires trivial hardware modification to basic router architectures, which incurs negligible power consumption and area cost.
Non-local adaptive routing techniques, which utilize statuses of both local and distant links to make routing decisions, have recently been shown to be effective solutions for promoting the ...performance of Network-on-Chip (NoC). The essence of non-local adaptive routing was an additional network dedicated to propagate congestion information of distant links on the NoC. While the dedicated Congestion Propagation Network (CPN) helps routers to make promising routing decisions, it incurs additional wiring and power costs and becomes an unnecessary decoration when the load of NoC is light. Moreover, the CPN has to be extended if one would utilize more sophisticated congestion information to enhance the performance of NoC, bringing in even larger wiring and power costs. This paper proposes an innovative non-local adaptive routing technique called FreeRider, which does not use a dedicated CPN but instead leverages free bits in head flits of existing packets to carry and propagate rich congestion information without introducing additional wires or flits. In order to balance the network load, FreeRider adopts a novel three-stage strategy of output link selection, which adequately utilizes the propagated information to make routing decisions. Experimental results on both synthetic traffic patterns and application traces show that FreeRider achieves better throughput, shorter latency, and smaller power consumption than a state-of-the-art adaptive routing technique with dedicated CPN.
To understand the molecular mechanism involved in the survivability of cold-tolerant lactic acid bacteria was of great significance in food processing, since these bacteria play a key role in a ...variety of low-temperature fermented foods. In this study, the cold-stress response of probiotic Lactobacillus plantarum K25 isolated from Tibetan kefir grains was analyzed by iTRAQ proteomic method. By comparing differentially expressed (DE) protein profiles of the strain incubated at 10℃ and 37℃, 506 DE proteins were identified. The DE proteins involved in carbohydrate, amino acid and fatty acid biosynthesis and metabolism were significantly down-regulated, leading to a specific energy conservation survival mode. The DE proteins related to DNA repair, transcription and translation were up-regulated, implicating change of gene expression and more protein biosynthesis needed in response to cold stress. In addition, two-component system, quorum sensing and ABC (ATP-binding cassette) transporters also participated in cell cold-adaptation process. These findings provide novel insight into the cold-resistance mechanism in L. plantarum with potential application in low temperature fermented or preserved foods.
Non-circular-cross-section tubes are widely used as heat exchange components throughout the industry, including in fields such as aerospace, automobiles, and vessels. Tube manufacturing in these ...fields is a highly complex process; to manufacture the needed tubes and guarantee a precise and stress-free assembly, the geometric parameters should be measured during manufacturing and before assembly. However, current studies and manufacturing instrumentation focus on tubes of circular cross section. This study proposes an extraction method for the tubular 3D skeleton of non-circular-cross-section tubes based on multi-view vision. Then, non-circular-cross-section tubes can be measured based on the proposed method. The experimental results show that the average deviation does not exceed 0.3 mm with <inline-formula> <tex-math notation="LaTeX">3\sigma </tex-math></inline-formula> reliability and the measuring time is fewer than 5 s. The accuracy and efficiency of this method are sufficient to satisfy the requirements for industrial applications.
The typical motion estimation (ME) consists of three main steps, including spatial-temporal prediction, integer-pel search, and fractional-pel search. The integer-pel search, which seeks the best ...matched integer-pel position within a search window, is considered to be crucial for video encoding. It occupies over 50% of the overall encoding time (when adopting the full search scheme) for software encoders, and introduces remarkable area cost, memory traffic, and power consumption to hardware encoders. In this paper, we find that video sequences (especially high-resolution videos) can often be encoded effectively and efficiently even without integer-pel search. Such counter-intuitive phenomenon is not only because that spatial-temporal prediction and fractional-pel search are accurate enough for the ME of many blocks. In fact, we observe that when the predicted motion vector is biased from the optimal motion vector (mainly for boundary blocks of irregularly moving objects), it is also hard for integer-pel search to reduce the final rate-distortion cost: the deviation of reference position could be alleviated with the fractional-pel interpolation and rate-distortion optimization techniques (e.g., adaptive macroblock mode). Considering the decreasing proportion of boundary blocks caused by the increasing resolution of videos, integer-pel search may be rather cost-ineffective in the era of high-resolution. Experimental results on 36 typical sequences of different resolutions encoded with x264, which is a widely-used video encoder, comply with our analysis well. For 1080p sequences, removing the integer-pel search saves 57.9% of the overall H.264 encoding time on average (compared to the original x264 with full integer-pel search using default parameters), while the resultant performance loss is negligible: the bit-rate is increased by only 0.18%, while the peak signal-to-noise ratio is decreased by only 0.01 dB per frame averagely.
There are a lot of complex tubing in aviation, aerospace, automobile, and other industrial machinery and equipment. The reliable assembly of these tubing directly affects the quality of the products. ...Tube has two targets in assembly including assembly performance and avoiding obstacles. Thus, the assembly results is an overall merit based on the geometry error. It is easy to get geometry error of a tube, but the problem is how to evaluate the assembly result according to the geometric errors. The current approaches have a good performance in analysis of idealized assembly. However bend tubes have complex topology and shape, current solvers cannot account for the natural manufacturing and assembly variability that occurs in assembly of bend tubes. In order to make accurate predictions about assembly performance and product quality, the variability of the assembled tubes must be evaluated in the assembly model. This article outlines two key targets in tube assembly based on the function of bend tube. To achieve the assembly targets, a method based on virtual fixture is proposed to evaluate the bend tube assembly performance. The evaluated bend tubes are adapted by the virtual fixtures and reach to an exact position to evaluate the assembly performance. Numerical experiments with Monte Carlo method are designed to simulate the method, analyze the results, and prove its feasibility. Designers and manufacturing engineers can efficiently evaluate the assembly performance or judge the assembly ability of a produced tube from its geometric errors.