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Desiccation cracking during water evaporation is a common phenomenon in soda saline–alkali soils and is mainly determined by soil salinity. Therefore, quantitative measurement of the surface cracking status of soda saline–alkali soils is highly significant in different applications. Texture features can help to determine the mechanical properties of soda saline–alkali soils, thus improving the understanding of the mechanism of desiccation cracking in saline–alkali soils. This study aims to provide a new standard describing the surface cracking conditions of soda saline–alkali soil on the basis of gray-level co-occurrence matrix (GLCM) texture analysis and to quantitatively study the responses of GLCM texture features to soil salinity. To achieve this, images of 200 field soil samples with different surface cracks were processed and calculated for GLCMs under different parameters, including directions, gray levels, and step sizes. Subsequently, correlation analysis was then conducted between texture features and electrical conductivity (EC) values. The results indicated that direction had little effect on the GLCM texture features, and that four selected texture features, contrast (CON), angular second moment (ASM), entropy (ENT), and homogeneity (HOM), were the most correlated with EC under a gray level of 2 and step size of 1 pixel. The results also showed that logarithmic models can be used to accurately describe the relationships between EC values and GLCM texture features of soda saline–alkali soils in the Songnen Plain of China, with calibration R2 ranging from 0.88 to 0.92, and RMSE from 2.12 × 10−4 to 9.68 × 10−3, respectively. This study can therefore enhance the understanding of desiccation cracking of salt-affected soil to a certain extent and can also help to improve the detection accuracy of soil salinity.

Glasses-free light field displays have significantly progressed due to advances in high-resolution microdisplays and high-end graphics processing units (GPUs). However, for near-eye light-field displays requiring portability, the fundamental trade-off regarding achieved spatial resolution remains: retinal blur quality must be degraded; otherwise, computational consumption increases. This has prevented synthesizing the high-quality light field from being fast. By integrating off-the-shelf gaze tracking modules into near-eye light-field displays, we present wearable virtual reality prototypes supporting human visual system-oriented focus cues. An optimized, foveated light field is delivered to each eye subject to the gaze point, providing more natural visual experiences than state-of-the-art solutions. Importantly, the factorization runtime can be immensely reduced, since the image resolution is only high within the gaze cone. In addition, we demonstrate significant improvements in computation and retinal blur quality over counterpart near-eye displays.

Free radicals play a negative role during the thermal degradation of silicone rubber (SR). Quenching free radicals is proposed to be an efficient way to improve the thermal-oxidative stability of SR. In this work, a novel zirconium-containing polyhedral oligometallasilsesquioxane (Zr-POSS) with free-radical quenching capability was synthesized and characterized. The incorporation of Zr-POSS effectively improved the thermal-oxidative stability of SR. The T5 (temperature at 5% weight loss) of SR/Zr-POSS significantly increased by 31.7 °C when compared to the unmodified SR. Notably, after aging 12 h at 280 °C, SR/Zr-POSS was still retaining about 65%, 60%, 75%, and 100% of the tensile strength, tear strength, elongation at break, and hardness before aging, respectively, while the mechanical properties of the unmodified SR were significantly decreased. The possible mechanism of Zr-POSS for improving the thermal-oxidative stability of SR was intensively studied and it was revealed that the POSS structure could act as a limiting point to suppress the random scission reaction of backbone. Furthermore, Zr could quench the free radicals by its empty orbital and transformation of valence states. Therefore, it effectively suppressed the thermal-oxidative degradation and crosslinking reaction of the side chains.

Terahertz (THz) impulse imaging has many applications in security and nondestructive testing. Sparse THz arrays can dramatically reduce array complexity for imaging applications requiring a large field of view. Sparse arrays employing narrowband waves suffer from grating lobe artifacts that severely degrade image quality. However, the short coherence length of single-cycle THz pulses provides an opportunity to overcome this limitation. Grating lobe artifacts can be suppressed with an adaptive weighting factor based on the temporal coherence of signals from neighboring array elements. The spatial coherence of signals across the entire array can further improve image quality in an adaptive manner. We experimentally demonstrate a 56 × 56 element 2-D sparse THz array that adaptively suppresses grating lobe artifacts by 30 dB. The success of this adaptive processing relies on the single-cycle nature of the pulses employed in THz impulse imaging.

Considering the characters of flow field for nature scenes, this paper applies GPU-based LBM computing into rendering natural scenes with large-scale particle system. We present a new Frame Buffer Object (FBO), multi-channel rendering process and GPU-based particle system combination methods. We propose a new GPU-based rendering pipeline to update the velocity of Boltzmann flow field and the positions of particles through two GPU textures at the same time. Finally, several natural scenes, such as spreading smokes, moving fog, snowing and scattered petals, are realistically simulated in real time.

Terahertz (THz) imaging is promising for nondestructive evaluation, since many optically opaque dielectrics are transparent to THz waves. Conventional THz imaging systems employ focusing elements such as spherical lenses and off-axis parabolas, but their fixed focal length produces an inherent trade-off between lateral resolution and depth of focus. Furthermore, image quality suffers when imaging objects located inside a dielectric medium. The air-dielectric interface introduces significant spherical aberration that degrades spatial resolution. Bessel beams are known to produce a small spot size over a large depth of focus. The contribution of our work is two-fold: (1) We demonstrate THz imaging with a significantly improved depth of focus using a zero-th order Bessel beam produced by an axicon lens. (2) We also demonstrate, for the first time to our knowledge, that Bessel beams experience reduced spherical aberration when imaging objects embedded in a dielectric medium. Imaging experiments are performed with a time-domain THz system, where a zero-th order quasi-Bessel beam is formed with an axicon lens made from high density polyethylene (HDPE). The HDPE axicon has a 50 mm diameter and an apex angle of 120 degrees. Point spread function (PSF) measurements confirm that lateral resolution is maintained over a 25 mm depth of field in air. The same lateral resolution is achieved over a 35 mm range inside a HDPE substrate. Needle objects embedded inside a thick HDPE substrate are imaged with high spatial resolution. Image contrast is significantly improved by digital filtering to reduce sidelobe levels. These promising results suggest that Bessel beams are well suited for terahertz nondestructive imaging of thick dielectric objects.

Sparse arrays are highly attractive for implementing two-dimensional arrays, but come at the cost of degraded image quality. We demonstrate significantly improved performance by exploiting the coherent ultrawideband nature of singlecycle THz pulses. We compute two weighting factors to each time-delayed signal before final summation to form the reconstructed image. The first factor employs cross-correlation analysis to measure the degree of walk-off between timedelayed signals of neighboring elements. The second factor measures the spatial coherence of the time-delayed delayed signals. Synthetic aperture imaging experiments are performed with a THz time-domain system employing a mechanically scanned single transceiver element. Cross-sectional imaging of wire targets is performed with a onedimensional sparse array with an inter-element spacing of 1.36 mm (over four λ at 1 THz). The proposed image reconstruction technique improves image contrast by 15 dB, which is impressive considering the relatively few elements in the array. En-face imaging of a razor blade is also demonstrated with a 56 x 56 element two-dimensional array, showing reduced image artifacts with adaptive reconstruction. These encouraging results suggest that the proposed image reconstruction technique can be highly beneficial to the development of large area two-dimensional THz arrays.

We demonstrate an adaptive reconstruction technique to significantly improve the depth of focus and contrast of three-dimensional reflection-mode terahertz imaging. A laterally scanned virtual transceiver element records reflections from the object of interest. A synthetic aperture focusing technique maintains fine spatial resolution over a large image depth. Measuring the spatial coherence of the received signals across the transceiver aperture provides a non-iterative self-adaptive approach to significantly improve image contrast. Test images show a spatial resolution of 0.4 mm maintained over a 16 mm depth of field, and up to a 30 dB improvement in signal-to-noise ratio.

Based on the infrared radiation characters of outer space targets and environment, considering the technologies related to the infrared star grade, atmosphere attenuation, and coordinate transformation, this paper builds the theoretical model of infrared radiation from flying satellites and background. Furthermore, using the database management of satellites orbits and catalogue data, the dynamic scene image synthesis of satellites and background is implemented. Finally, we can walkthrough the virtual scenes from different viewports, and analyze the characters of these dynamic simulating images. Research results have significance for space targets exploration, identify and tracking.

A service-oriented software reengineering is essential for legacy systems to survive in the service-oriented computing environment. In this paper, a method for the identification of reusable legacy code is proposed to support Service-Oriented Software Reengineering (SOSR).Ontologies for SOSR, which consist of Domain Concept Ontology (DCO), Functionality Ontology (FO) and Software Component Ontology (SCO), are defined and developed. These ontologies store knowledge of both application domain and code entities, which support further legacy code analysis. Based on SCO, the identification of service candidates in legacy systems is achieved by mapping FO and SCO via a novel method combining Formal Concept Analysis (FCA) and Relational Concept Analysis (RCA). The case study shows that the method can help software developers and maintainers to reengineer the tightly coupled legacy information systems to the loosely coupled and agile information systems.

Understanding and maintaining legacy COBOL systems are still a challenging task for both academic research and industry practice. With the development of aspect-oriented software engineering, aspect-oriented code comprehension and reengineering for COBOL software systems become a very promising research direction. In this paper, context aspect and error handling aspect, which are two most important aspects for COBOL code understanding, are defined. Furthermore, the approach for aspect location and operations in COBOL code is presented. Program slicing technique is adopted to locate aspect code from large COBOL systems. This paper reports our experience to date on the application of aspect-oriented program understanding in COBOL code, and more future work will be carry out shortly.

Many legacy systems were developed in COBOL, which still play an important role in business. It is an unavoidable issue for organisations to maintain or replace these COBOL systems. In order to make a better use of these legacy COBOL systems, research on modelling and reusing COBOL code are significant. This paper presents an approach to modelling legacy COBOL code with UML collaboration diagrams via a Wide Spectrum Language (WSL). Firstly, legacy COBOL code is transferred into WSL, which is an intermediate language. Secondly, WSL representation is restructured to eliminate GOTO statements. Then an object concept model is created by operating WSL representation. Finally, the collaboration diagrams are constructed based on this object concept model. These collaboration diagrams express the dynamic behaviour of the system, using the structural class and relationship elements of the model, and facilitate engineers to understand and reuse legacy COBOL code.

We demonstrate a noniterative adaptive reconstruction technique to significantly improve the imaging performance of sparse terahertz arrays employing single-cycle pulses. Grating lobe artifacts are suppressed by an adaptive weighting factor derived from the temporal coherence of signals from neighboring array elements. Image quality is further improved by a second weighting factor based on the spatial coherence of signals across the entire array. Experiments are performed with a synthetic aperture two-dimensional sparse array of 56x56 elements. Our reconstruction technique suppresses artifacts by 30 dB.