Shift Distance Research Articles

Numerical study on size effect and anisotropy of columnar jointed basalts under uniaxial compression

Under uniaxial loading, the heterogeneity of rock mass, the change of mechanical properties of joints, and the progressive fracture process of rock mass significantly affect the size effect and anisotropy of columnar jointed basalts (CJBs). To reveal the fracture features and failure mechanisms of CJBs influenced by the size effect and anisotropy, the digital image correlation (DIC), meso-damage mechanics, statistical strength theory, and continuum mechanics were combined (the DIC-improved RFPA), the digital images of CJB specimens were processed to establish the inhomogeneous numerical models, and a series of numerical tests were therefore conducted. The gradual fracture processes and macro failure patterns of CJBs orthogonal and parallel to column axis under uniaxial compression were studied, and the effects of various factors on the size effect and anisotropic mechanical properties of CJBs were further analyzed. The results show that model size, column dip angle, rock heterogeneity, column diameter, elastic modulus of joints, residual strength coefficient of joints, ratio of shift distance of joints, irregularity degrees of columns, and model boundaries have remarkable and complex effects on the mechanical behaviors of CJBs. The results greatly improve our understanding of the non-linear deformation and failure behaviors of CJBs and provide theorical basis for engineering construction in the areas of CJBs.

Combined Methodology for Accurate Evaluation of Distance and Direction of Chromaticity Shifts in LED Reliability Tests

Light Emitting Diodes are an integral part of modern illumination systems. While their long-term stability in terms of lumen maintenance used to be in the focus leading to drastically increased nominal lifetimes over the past decade, the color shift or respectively chromaticity shift is lately attracting more and more attention especially in lighting applications that demand for a high chromatic stability. Common ways of displaying and reporting color shifts in LEDs and LED products provide only limited possibilities to accurately classify changes in color according to the current understanding of the underlying degradation processes. This paper therefore presents a methodology to overcome the observed discrepancies in analyzing time-dependent chromaticity data in terms of their shift direction and distance within the CIE 1976 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$u',v'$ </tex-math></inline-formula> ) chromaticity diagram. The use of an extrapolation function extending the shift towards the spectral locus enables the determination of the corresponding nearest spectral locus intersection wavelength. Thereby, it is possible to classify changes in color according to different shift regions, which basically allows for performing an automated comprehensive color shift mode analysis. As part of this paper five different algorithmic approaches for determining the intersection wavelength and shift region are discussed and compared in terms of their accuracy and ease in implementation.

Influence of Misalignment on the Behavior of Electron Beam of an 800 GHz Gyrotron

The operation of gyrotrons highly depends on the alignment between the magnet and the tube, which will cause instability problems or degrade the output efficiency, especially for high-frequency gyrotrons with a small cavity size. In this letter, the influence of misalignment, including parallel shift, arbitrary tilt, and their co-existence, on the behavior of the electron beam was studied. A prototype of an 800 GHz gyrotron with a sapphire window was developed to study the correlation between the misalignment and the beam trajectory. A method to determine the tilt angle and shift distance was proposed. The feasibility of the misalignment correction method was verified in the experiment.

Bilanthanide Metal–Organic Frameworks for Instant Detection of 17β‐Estradiol, a Vital Physiological Index

Bilanthanide metal–organic frameworks (MOFs) have promising sensing applications for specific molecules because enhanced sensing functions can be achieved by the dual emissions from bilanthanide centers. In general, chemical mixture or physical mixture of two lanthanide MOFs can both produce dual emissions. However, the advantages of chemical mixture over physical mixture of lanthanide MOFs as sensing materials are not experimentally demonstrated in detail. Herein, a bilanthanide MOF‐based luminescent sensor of NKU‐103(EuTb) synthesized by mixed‐lanthanide strategy for the identification of 17β‐estradiol, a vital diagnostic clinical biomarker, is reported. The dual emission of NKU‐103(EuTb) is able to effectively remove systematic errors, confirmed by varying the slit width, the excitation wavelength, and the concentration. The quenching efficiency ratio and shift distance of Commission Internationale de l’É clairage (CIE) coordinates of NKU‐103(EuTb) are higher than the physical mixture of NKU‐103(Eu) and NKU‐103(Tb), which demonstrates for the first time the superiority of MOF‐based sensing materials by the chemical mixed‐lanthanide strategy.

An optimized natural convection Y-shape-shifted heat sink design problem

An optimized design problem for a natural convection three-dimensional Y-shape-shifted heat sink is investigated numerically and experimentally in the present study. The software package CFD-ACE+ and the Levenberg-Marquardt method (LMM) are utilized as the numerical solution solver and design tool, respectively. The objective of this work is to design the optimal fin stem height, fin branch length, branching angle, and shift distance of the Y-shaped fin under fixed Y-shaped fin volume conditions to minimize the base plate temperature and enhance the cooling performance of the heat sink. The thermal radiation effect between the air and Y-shaped fin is considered in this work to improve the accuracy of the numerical solution of temperatures. The result indicates that in the optimized Y-shaped heat sink, the stem height and branching angle become shorter and larger, respectively, than those of the original design. When the shift distance is considered as a design variable, i.e., the optimized Y-shape-shifted heat sink with an up-up-up fin displacement arrangement, the chimney-flow effect due to the buoyant plume is much more pronounced than that of the original design, and a pair of longitudinal vortices also occur; therefore, better heat dissipation performance can be achieved. Experiments were performed on manufactured heat sinks to check the validity of the design results. The results indicated that the measured temperatures of the heat sinks are very close to the computed data since the maximum error between the computed and measured base temperatures is less than 0.81%. In addition, design B1 (a vertical heat sink) has the smallest thermal resistance Rth among all designs at 2.6% smaller than that of the original vertical heat sink, which confirms the validity of the present work in designing the optimal design of the Y-shape-shifted heat sink.

The total resection rate of glioma can be improved by the application of US-MRI fusion combined with contrast-enhanced ultrasound

ObjectiveThis study was performed to evaluate the diagnostic performance of ultrasound-magnetic resonance imaging (MRI) fusion combined with contrast-enhanced ultrasound and to explore its role in improving the total tumor resection rate. MethodsBetween January 2018 and December 2018, 16 patients in the observation group and 23 patients in the control group were enrolled in this study. The tumor depth and brain shift distance were analyzed, as well as the peak intensity and microvessel density of different grades of gliomas in the observation group. Finally, we compared the difference in total resection rate between the observation and control groups. ResultsUsing ultrasound during operations, we found a significant negative correlation between brain shift distance and tumor depth, with correlation coefficient r=−0.868(P<0.05). In glioma, the peak intensity and microvessel density increased synchronously with glioma grade(r=0.806, P<0.05). The total resection rate of lesions was significantly higher in the observation group than in the control group (P<0.05). ConclusionsThe application of ultrasound-MRI fusion combined with contrast-enhanced ultrasound can improve the total resection rate of lesions, thus playing an important role in clinical practice.

Customizing the following behavior models to mimic the weak lane based mixed traffic conditions

This study aims to model traffic flow under weak lane based heterogonous (mixed) traffic conditions. Unlike homogeneous traffic, when a follower (subject) vehicle in mixed traffic moves closer to its leader vehicle, it tends to adjust its longitudinal movement or change its lane and acts discretely. Due to this phenomenon, traffic flow modeling under such conditions is always challenging. A new driver behavioral logic is conceptualized for the vehicles’ movement within a combination of surrounding vehicles. In which the following behavior was dissected with the lateral shift distance between vehicles. Two car-following models for homogeneous traffic conditions, the IDM and Gipps models were adapted with relevant lateral behavior parameters to different vehicle classes under mixed-traffic conditions. The new driving behavior logic was incorporated externally in place of default logic. The results showed that the performance of the adapted models was better accurate than the classical models.

Scenarios of potential vegetation distribution in the different gradient zones of Qinghai-Tibet Plateau under future climate change

The spatial distribution of potential vegetation types in Qinghai-Tibet Plateau presents a significant vertical zonation. Explicating the vertical differences of potential vegetation distribution under future climate change in Qinghai-Tibet Plateau is an important issue for understanding the response of terrestrial ecosystem to climate change. Based on the observed climate data in 1981–2010 (T0), the scenario data of RCP 2.6, RCP 4.5 and RCP 8.5 released by CMIP5 in 2011–2040 (T1), 2041–2070 (T2) and 2071–2100 (T3), and the digital elevation model (DEM) data, the Holdridge life zone (HLZ) model has been improved to simulate the scenarios of potential vegetation distribution in the different gradient zones of Qinghai-Tibet plateau. The shift model of mean center has been improved to calculate the shift direction and distance of mean center in the potential vegetation types. The ecological diversity index was introduced to compute the ecological diversity change of potential vegetation. The simulated results show that there are 17 potential vegetation types in Qinghai-Tibet Plateau. Wet tundra, high-cold moist forest and nival are the major potential vegetation types and cover 56.26% of the total area of Qinghai-Tibet Plateau. Under the three scenarios, the nival would have the largest decreased area that would be decreased by 3.340 × 104 km2 per decade, and the high-cold wet forest would have the greatest increased area that would be increased by 3.340 × 104 km2 on average per decade from T0 to T3. The potential vegetation types distributed in the alpine zone would show the fastest change ratio (11.32% per decade) and that in low mountain and other zone would show the slowest change ratio (7.54% per decade) on average. The ecological diversity and patch connectivity of potential vegetation would be decreased by 0.108% and 0.290% per decade on average from T0 to T3. In general, the potential vegetation types distributed in the high elevation area generally have a higher sensitivity to climate change in Qinghai-Tibet plateau in the future.

Monitoring the Spatiotemporal Trajectory of Urban Area Hotspots Using the SVM Regression Method Based on NPP-VIIRS Imagery

Urban area hotspots are considered to be an ideal proxy for spatial heterogeneity of human activity, which is vulnerable to urban expansion. Nighttime light (NTL) images have been extensively employed in monitoring current urbanization dynamics. However, the existing studies related to NTL images mainly concern detection of urban areas, leaving inner spatial differences in urban NTL luminosity poorly explored. In this study, we propose an innovative approach to explore the spatiotemporal trajectory of urban area hotspots using monthly Visible Infrared Imaging Radiometer Suite (VIIRS) NTL images. Firstly, multi-temporal VIIRS NTL intensity was decomposed by time-series analysis to obtain annual stable components after data preprocessing. Secondly, the support vector machine (SVM) regression model was utilized to identify urban area hotspots. In order to ensure the model accuracy, the grid search and cross-validation method was integrated to achieve the optimized model parameters. Finally, we analyzed the spatiotemporal migration trajectory of urban area hotspots by the center of gravity method (i.e., shift distance and angle of urban area hotspot centroid). The results indicate that our method successfully captured urban area hotspots with a regression coefficient over 0.8. Meanwhile, the findings give an intuitive understanding of coupling interaction between urban area hotspots and socioeconomic indicators. This study provides important insights for further decision-making regarding sustainable urban planning.

Breaking the symmetry to structure light.

We show that by breaking the symmetry of a beam subjected to tight focusing, namely by obscuring half of it or, equivalently, shifting the beam away from the lens axis, it is possible to obtain novel light properties in the focal spot which, to the best of our knowledge, have not been observed before. For example, a linearly polarized beam half-obstructed or shifted from the axis generates longitudinal and transverse electrical field components, both of which peak on-axis. The ratio of the intensities of these two components can be tuned by changing the shift distance, the size, and the azimuthal location of the displaced incoming beam. Moreover, such symmetry breaking of a linearly polarized beam acts as a catalyst for producing distributions of circular polarization/longitudinal spin angular momentum, as well as orbital angular momentum, in the focal plane. The simple method for generating co-incident longitudinal and transverse components with a controllable ratio may find applications in laser machining, particle manipulation, etc.

Research on the influence of foaming gas in compressed air/nitrogen foam on extinguishing the n-heptane tank fire

Tank fires threaten the lives of people and pollute the environment for their intense radiant heat, rapid fire spread and explosion hazard. Compressed air/nitrogen foam (CAF/CNF), a cleaner fire extinguishing technique used for the tank fire suppression because halogen-based agents were prohibited for environmental reasons. In this work, the influence of foaming gas in CAF/CNF on extinguishing the n-heptane tank fire was firstly investigated. Firstly, it was found that CNF spreads faster with rapid increase in foam thickness, mainly due to its better stability and less evaporation. Secondly, after foam was discharged, there existed a short increase of the combustion intensity, associated with three monotonous regions and two time delays in the whole extinguishing time. The two time delays were caused by Rayleigh–Taylor instability and flame sheet shift, respectively, and the shift distance was larger for CNF. Finally, the influential factors contributing to flame extinction were exhibited to be mainly related to the decrease in liquid burning rate and gas-phase Damkohler number. Among these factors, foam spreading rate and thickness dominated due to coupled chemical and physical extinguishing effects. Resulted from some competitive effects, CNF was slightly more efficient at extinguishing tank fires than CAF.

Validation of a 4D-MRI guided liver stereotactic body radiation therapy strategy for implementation on the MR-linac

Purpose. Accurate tumor localization for image-guided liver stereotactic body radiation therapy (SBRT) is challenging due to respiratory motion and poor tumor visibility on conventional x-ray based images. Novel integrated MRI and radiotherapy systems enable direct in-room tumor visualization, potentially increasing treatment accuracy. As these systems currently do not provide a 4D image-guided radiotherapy strategy, we developed a 4D-MRI guided liver SBRT workflow and validated all steps for implementation on the Unity MR-linac. Materials and Methods. The proposed workflow consists of five steps: (1) acquisition of a daily 4D-MRI scan, (2) 4D-MRI to mid-position planning-CT rigid tumor registration, (3) calculation of daily tumor midP misalignment, (4) plan adaptation using adapt-to-position (ATP) with segment-weights optimization and (5) adapted plan delivery. The workflow was first validated in a motion phantom, performing regular motion at different baselines (±5 to ±10 mm) and patient-derived respiratory signals with varying degrees of irregularity. 4D-MRI derived respiratory signals and 4D-MRI to planning CT registrations were compared to the phantom input, and gamma and dose-area-histogram analyses were performed on the delivered dose distributions on film. Additionally, 4D-MRI to CT registration performance was evaluated in patient images using the full-circle method (transitivity analysis). Plan adaption was further analyzed in-silico by creating adapted treatment plans for 15 patients with oligometastatic liver disease. Results. Phantom trajectories could be reliably extracted from 4D-MRI scans and 4D-MRI to CT registration showed submillimeter accuracy. The DAH-analysis demonstrated excellent coverage of the dose evaluation structures GTV and GTVTD. The median daily rigid 4D-MRI to midP-CT registration precision in patient images was <2 mm. The ATP strategy restored the target dose without increased exposure to the OARs and plan quality was independent from 3D shift distance in the range of 1–26 mm. Conclusions. The proposed 4D-MRI guided strategy showed excellent performance in all workflow tests in preparation of the clinical introduction on the Unity MR-linac.

Performance analysis of a two bladed Savonius water turbine cluster for perennial river-stream application at low water speeds

Mutual interactions of twin Savonius water turbines in cluster can augment the harness of water power from river stream currents without implementing additional device. For low speed water current (less than 1 m/s) applicable in perennial rivers, an efficient design of twin Savonius turbine cluster is not designed so far. The objective of the present study is to experimentally investigate the performance of two bladed cluster Savonius water turbines and perform numerical simulations using CFD to determine the configuration of an efficient cluster design. The cluster design is constructed using twin Savonius water turbines having same design features. Different configurations of the cluster are studied with respect to gap distance and phase shift between them. Detailed experimental investigations are carried out in an open flow water channel at a low water speed of 0.75 m/s by varying these two parameters to determine their optimal values for an efficient cluster design. The results show a maximum power coefficient of 0.15 at a tip speed ratio 0.3 can be obtained for the cluster if the gap distance between the twin turbines is 0.6 times the turbine diameter and phase shift between them is 30°. A maximum power coefficient of only 0.075 is obtained at the same tip speed ratio for only two bladed Savonius water turbine, which is half of that of the efficient cluster design. Further, flow physics of the individual turbines in cluster are obtained to delineate the importance of proper phase shift and gap distance to make an efficient cluster design. The present study demonstrates the potential of twin Savonius water turbine cluster design as a river-stream energy harvester for small-scale power generation in rural areas.

Application of Satellite Sentinel-2 Images to Study Alternate Sandbars Movement at Lower Vistula River (Poland)

The lower Vistula River was regulated in the years 1856–1878, at a distance of 718–939 km. The regulation plan did not take into consideration the large transport of the bed load. The channel was shaped using simplified geometry—too wide for the low flow and overly straight for the stabilization of the sandbar movement. The hydraulic parameters of the lower Vistula River show high velocities of flow and high shear stress. The movement of the alternate sandbars can be traced on the optical satellite images of Sentinel-2. In this study, a method of sandbar detection through the remote sensing indices, Sentinel Water Mask (SWM) and Automated Water Extraction Index no shadow (AWEInsh), and the manual delineation with visual interpretation (MD) was used on satellite images of the lower Vistula River, recorded at the time of low flows (20 August 2015, 4 September 2016, 30 July 2017, 20 September 2018, and 29 August 2019). The comparison of 32 alternate sandbar areas obtained by SWM, AWEInsh, and MD manual delineation methods on the Sentinel-2 images, recorded on 20 August 2015, was performed by the statistical analysis of the interclass correlation coefficient (ICC). The distance of the shift in the analyzed time intervals between the image registration dates depends on the value of the mean discharge (MQ). The period from 30 July 2017 to 20 September 2018 was wet (MQ = 1140 m3 × s−1) and created conditions for the largest average distance of the alternate sandbar shift, from 509 to 548 m. The velocity of movement, calculated as an average shift for one day, was between 1.2 and 1.3 m × day−1. The smallest shift of alternate sandbars was characteristic of the low flow period from 20 August 2015 to 4 September 2016 (MQ = 306 m3 × s−1), from 279 to 310 m, with an average velocity from 0.7 to 0.8 m × day−1.

Spatial identification and scenario simulation of the ecological transition zones under the climate change in China

Explicitly identifying the spatial distribution of ecological transition zones (ETZs) and simulating their response to climate scenarios is of significance in understanding the response and feedback of ecosystems to global climate change. In this study, a quantitative spatial identification method was developed to assess ETZ distribution in terms of the improved Holdridge life zone (iHLZ) model. Based on climate observations collected from 782 weather stations in China in the T0 (1981–2010) period, and the Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project (IPCC CMIP5) RCP2.6, RCP4.5, and RCP8.5 climate scenario data in the T1 (2011–2040), T2 (2041–2070), and T3 (2071–2100) periods, the spatial distribution of ETZs and their response to climate scenarios in China were simulated in the four periods of T0, T1, T2, and T3. Additionally, a spatial shift of mean center model was developed to quantitatively calculate the shift direction and distance of each ETZ type during the periods from T0 to T3. The simulated results revealed 41 ETZ types in China, accounting for 18% of the whole land area. Cold temperate grassland/humid forest and warm temperate arid forest (564,238.5 km2), cold temperate humid forest and warm temperate arid/humid forest (566,549.75 km2), and north humid/humid forest and cold temperate humid forest (525,750.25 km2) were the main ETZ types, accounting for 35% of the total ETZ area in China. Between 2010 and 2100, the area of cold temperate desert shrub and warm temperate desert shrub/thorn steppe ETZs were projected to increase at a rate of 4% per decade, which represented an increase of 3604.2, 10063.1, and 17,242 km2 per decade under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. The cold ETZ was projected to transform to the warm humid ETZ in the future. The average shift distance of the mean center in the north wet forest and cold temperate desert shrub/thorn grassland ETZs was generally larger than that of other ETZs, with the mean center moving to the northeast and the shift distance being more than 150 km during the periods from T0 to T3. In addition, with a gradual increase of temperature and precipitation, the ETZs in northern China displayed a shifting northward trend, while the area of ETZs in southern China decreased gradually, and their mean center moved to high-altitude areas. The effects of climate change on ETZs presented an increasing trend in China, especially in the Qinghai-Tibet Plateau.

Enhanced light extraction efficiency and viewing angle characteristics of microcavity OLEDs by using a diffusion layer

The viewing angle characteristics and light extraction efficiency of organic light-emitting diodes (OLEDs) with a micro-cavity structure were enhanced. This was accomplished by inserting a diffusion layer composed of nano-sized structures of a transparent polymer poly(methyl methacrylate) (PMMA) combined with a zinc oxide (ZnO) semi-planarization layer with a high refractive index (n = 2.1) into the devices. The PMMA nanostructures were fabricated by employing a reactive ion etching (RIE) process. The height and density of the PMMA nanostructures were controlled by varying the speed at which the PMMA was spin-coated onto the substrate. The insertion of the diffusion layer into the micro-cavity OLEDs (MC-OLEDs) improved the external quantum efficiency (EQE) by as much as 17% when compared to that of a MC-OLED without a diffusion layer. Furthermore, adjustment of the viewing angle from 0° to 60° halved the peak shift distance of the electroluminescence (EL) spectra from 42 to 20 nm. Additionally, changing the viewing angle from 0° to 60° changed the color coordinate movement distance of the MC-OLED with the diffusion layer to 0.078, less than half of the distance of the MC-OLED without the diffusion layer (0.165).

Accommodation and binocular vision changes after wearing orthokeratology lens in 8- to 14-year-old myopic children

The study aimed to observe and analyze the dynamic accommodation and binocular vision changes in myopic children after they switched from spectacles to orthokeratology (ortho-k) lenses. Thirty-six myopic children aged 8-14 years were enrolled in this prospective, self-controlled study from West China Hospital. General information was gathered, and examinations were performed at baseline and at 1, 3, 6, and 12 months after switching to ortho-k lenses. The examination included assessments of distance/near visual acuity, distance/near horizontal and vertical ocular alignment, distance/near horizontal vergence range, accommodative amplitude, monocular/binocular accommodative facility, accommodative response, positive and negative relative accommodation (PRA/NRA), accommodation convergence/accommodation (AC/A), stereopsis, and reading ability. After the children switched to ortho-k lenses, distance and near ocular alignment showed an exophoric shift (distance: p = 0.001, near: p = 0.002), and the horizontal vergence range decreased by different degrees (convergence: distance blur point (p = 0.002), distance break point (p = 0.005), near blur point (p = 0.011), near break point (p = 0.043); divergence: distance break point (p < 0.001), distance recover point (p < 0.001), near recover point (p = 0.005)). The stereopsis ability (p < 0.001), monocular/binocular accommodative facility (p < 0.001), and PRA (p = 0.010) increased. The accommodative lag (p < 0.001), accommodative amplitude (p < 0.001), and calculated and gradient AC/A (calculated: p = 0.001, gradient: p = 0.025) decreased. The adjusted horizontal and vertical reading times and their ratio decreased (all p < 0.001). The subjects showed distance and near exophoric shifts after switching to ortho-k lenses; improvements in accommodative function, stereopsis, and ocular motility; and a decrease in the binocular horizontal vergence range. The relationships between these changes and the ortho-k myopic control effects require further investigation.

青藏高原植被生态系统垂直分布变化的情景模拟

如何模拟和揭示青藏高原植被生态系统垂直分布在全球气候变化驱动下的时空变化情景，对定量解析青藏高原陆地生态系统对气候变化响应效应具有重要意义。该论文基于Holdridge life zone （HLZ）模型，结合数字高程模型（DEM）数据，改变模型输入参数模式，发展了改进型HLZ生态系统模型。结合1981-2010（T0）时段的气候观测数据和IPCC CMIP5 RCP2.6、RCP4.5、RCP8.5三种情景2011-2040（T1）、2041-2070（T2）、2071-2100（T3）三个时段气候情景数据，实现了青藏高原植被生态系统垂直分布的时空变化情景模拟。引入生态系统平均中心时空偏移趋势模型和生态多样性指数模型，定量揭示了青藏高原植被生态系统在不同垂直带上的时空变化情景。结果显示：青藏高原共有16种植被生态系统类型；冰雪/冰原、高山潮湿苔原和亚高山湿润森林为青藏高原主要的植被生态系统类型，其面积之和占到了青藏高原总面积的56.26%；高山干苔原、亚高山潮湿森林、山地灌丛、山地湿润森林和荒漠等对气候变化的敏感性总体上高于其它类型；在T0-T3期间，青藏高原的高山湿润苔原、高山干苔原、荒漠呈持续减少趋势，平均每10年将分别减少1.96×10⁴km²、0.15×10⁴km²和1.58×10⁴km²；亚高山潮湿森林、山地湿润森林和山地灌丛呈持续增加趋势，平均每10年将分别增加3.42×10⁴km²、2.98×10⁴km²和1.19×10⁴km²；RCP8.5情景下青藏高原的植被生态系统平均中心的偏移幅度最大，RCP4.5情景下的偏移幅度次之，而RCP2.6情景下的偏移幅度最小。另外，在三种气候变化情景驱动下，青藏高原植被生态系统的生态多样性呈减少趋势。总之，未来不同情景的气候变化将直接影响青藏高原植被生态系统的时空分布格局及其生态多样性，气候变化强度越高，影响就越大，而且气候变化对青藏高原植被生态系统的影响呈现出从低海拔到高海拔递增的影响效应。;How to simulate and reveal the spatiotemporal change scenarios of vertical distribution of vegetation ecosystem in Qinghai-Tibet Plateau under the future global climate change is very beneficial for quantitatively explicating the response of terrestrial ecosystem to climate change. In this study, the improved Holdridge Life Zone (iHLZ) ecosystem model was developed by combing the HLZ model and Digital Elevation Model (DEM) data. Based on the climate observation data in the T0 (1981-2010) period, and the Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project (IPCC CMIP5) RCP2.6, RCP4.5, and RCP8.5 climate scenario data in the T1 (2011-2040), T2 (2041-2070), and T3 (2071-2100) periods, the vertical scenarios of vegetation ecosystem distributed in Qinghai-Tibet Plateau were simulated. The spatiotemporal shifting model of ecosystem mean center and ecological diversity index were introduced to explicitly analyze the change of vegetation ecosystem in different vertical zones of Qinghai-Tibet Plateau. The results show that there are 16 mountain vegetation ecosystem types in Qinghai-Tibet Plateau. The ice snow/ice, alpine moist tundra, and subalpine moist forest are the major vegetation ecosystem types and covers 56.26% of the total area of Qinghai-Tibet Plateau. -The sensitivity of alpine dry tundra, subalpine moist forest, mountain shrub, and desert to the climate change would be generally more than other types in Qinghai-Tibet Plateau under the three scenarios of RCP2.6, RCP4.5, and RCP8.5. The areas of alpine moist tundra, alpine dry tundra and desert show a decreasing trend, which will be decreased by 1.96×10⁴ km², 0.15×10⁴ km² and 1.58×10⁴ km² per decade between T0 and T3, respectively. The areas of subalpine moist forest, mountain moist forest and mountain shrub show an increasing trend, which will be increased by 3.42×10⁴ km², 2.98×10⁴ km² and 1.19×10⁴ km² per decade between T0 and T3, respectively. The mean center in the vegetation ecosystem has the largest shift distance under the scenario RCP8.5, followed by the scenario RCP4.5, and that has the least shift distance under the scenario RCP8.5. The ecological diversity of vegetation ecosystem will be reduced generally in Qinghai-Tibet Plateau in the future. In general, the greater climate change will lead to the larger impacts of climate change on ecosystem diversity, which shows an increasing trend from low altitude to high altitude in the Qinghai-Tibet Plateau.

Semiconductor Manufacturing Final Test Yield Optimization and Wafer Acceptance Test Parameter Inverse Design Using Multi-Objective Optimization Algorithms

In the semiconductor industry, many previous optimization studies have been carried out at the integrated circuit front-end design phase to identify optimal circuit elements’ size and design parameters. With the scaling of device dimensions, semiconductor manufacturing back-end Final Test (FT) yield is increasingly influenced by systematic or random process variations. As a result, the FT yield is not fully guaranteed by design phase optimization due to existing limitations of yield simulation models and coverage. Very few studies have attempted to incorporate the production FT yield data into process variation optimization and inverse design. In this paper, we introduce a novel framework for FT yield optimization and Wafer Acceptance Test (WAT) parameter inverse design using multi-objective optimization algorithms. This provides a solution to monitor and quickly adjust process variations to maximize FT yield without expensive characterization or design correction after products are released into the production phase. Both yield optimization and process shift feasibility are to be taken into consideration by formulating these factors into a two objective optimization problem. One objective is to minimize FT yield loss, wherein the yield loss is predicted by a machine learning model. The other objective is to minimize the total WAT parameters shift distance from the current standard setting. Three widely used multi-objective algorithms NSGA-II, SMPSO and GDE3 are applied, compared and discussed. An automatic parameter tuning approach using Sequential Model-based Algorithm Configuration (SMAC) and entropy-based termination criterion is applied to reduce the execution time whilst maintaining the optimization algorithms’ performance. Real production data for CMOS 55nm chip are used to validate the framework and the results point to the effectiveness of yield improvement and accurate identification of the optimal WAT parameter combination.

Shift of potential natural vegetation against global climate change under historical, current and future scenarios

Potential natural vegetation (PNV), the final successional stage of vegetation, plays a key role in ecological restoration, the design of nature reserves, and development of agriculture and livestock production. Meteorological data from historical and current periods including the last inter-glacial (LIG), last glacial maximum (LGM), mid Holocene (MH) periods and the present day (PD), plus derived data from 2050 and 2070, in conjunction with the Comprehensive and Sequential Classification System (CSCS) model, were used to classify global PNV. The 42 classes of global PNV were regrouped into 10 groups to facilitate analysis of spatial changes. Finally, spatio-temporal patterns and successional processes of global PNV as well as the response to climate changes were analysed. Our study made the following five conclusions. (1) Only one missing class (IA1 frigid-extrarid frigid desert, alpine desert) arose in periods of LIG, MH, 2050, and 2070 for global PNV. (2) The frigid-arid groups were mainly distributed in higher latitudes and elevations, but temperate-humid groups and tropical-perhumid groups occurred in middle and low latitudes, respectively. Temperate zonal forest steppe, warm desert, savanna and tropical zonal forest steppe increased, while six other groups decreased. (3) The conversion from temperate zonal forest steppe to tundra and alpine steppe from LIG to LGM occupied the largest area, indicating a drastic shift in climate and the associated response of terrestrial vegetation sensitive to climate change. (4) The CSCS could be used to simulate the long-term succession of global PNV. (5) As a consequence of global warming, forests shifted to the northern hemisphere and Tibet, areas with much higher latitude and elevation. The PNV groups with greater shift distance revealed the more serious effects of global climate change on vegetation.