Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potent...Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potential （PRVEP） and the visual acuity at particular visual angles. Methods Two hundred and ten volunteers were divided into seven groups, according to visual acuity as assessed by the standard logarithmic visual acuity chart （SLD-II）. For each group, the PRVEP components were elicited in response to visual angle presentations at 8°, 4°, 2°, 1°/60＇, 30＇, 15＇, and 7.5＇, in the whiteblack chess-board reversal mode with a contrast level of 100% at a frequency of 2 Hz. Visual stimuli were presented monocularly, and 200 presentations were averaged for each block of trials. The early and stable component P1 was recorded at the mid-line of the occipital region （Oz） and analyzed with SPSS 13.00. Results （1） Oz had the maximum Pl amplitude; there was no significant difference between genders or for interocular comparison in normal controls and subjects with optic myopia. （2） The P1 latency decreased slowly below 30＇, then increased rapidly. The P1 amplitude initially increased with check size, and was maximal at -1° and -30＇. （3） The P1 latency in the group with visual acuity 〈0.2 was signifi- cantly different at 8°, 15＇ and 7.5＇, while the amplitude differed at all visual angles, compared with the group with normal vision. Differences in P1 for the groups with 0.5 and 0.6 acuity were only present at visual angles 〈1°. （4） Regression analysis showed that the P1 latency and amplitude were associated with visual acuity over the full range of visual angles. There was a moderate correlation at visual angles 〈30＇. Regression equations were calculated for the P1 components and visual acuity, based on visual angle. Conclusion （1） Visual angle should be taken into consideration when exploring the function of the visual pathway, especially visual acuity. A visual angle -60＇ might be appropriate when using PRVEP com- ponents to evaluate poor vision and to identify malingerers. （2） Increased P1 amplitude and decreased P1 latency were as- sociated with increasing visual acuity, and the P1 components displayed a linear correlation with visual acuity, especially in the range of optimal visual angles. Visual acuity can be deduced from P 1 based on visual angle.展开更多
In exterior use, wood is subjected to weathering that causes checking and other deterioration in the appearance and technical properties. We studied quantitatively the surface checking of radially and tangentially saw...In exterior use, wood is subjected to weathering that causes checking and other deterioration in the appearance and technical properties. We studied quantitatively the surface checking of radially and tangentially sawn specimens of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies Karst.) wood in a cyclic climate chamber test. The results strongly suggested that the sawing direction determines the checking performance of both Scots pine and Norway spruce wood. The radial surface of Scots pine specimens had 62% less checks than the tangential one, and the cumulative area of checks was 74% smaller. For Norway spruce, the respective figures were: 83% less in the check number and 91% less in the check area. Different from pine, in spruce specimens the checks of radial surface were significantly smaller. Thus, spruce timber gained clearly more about radial sawing pattern. The effect of annual ring width was similar for pine and spruce: the reduction in annual growth worsened the checking. The increase in density worsened the checking of spruce but did not change the performance of pine. In pine wood, the increase of heartwood proportion reduced the fluctuation of moisture content and the formation of checks.展开更多
This article introduces a novel low rank approximation (LRA)-based model to detect the functional regions with the data from about 15 million social media check-in records during a year-long period in Shanghai, China....This article introduces a novel low rank approximation (LRA)-based model to detect the functional regions with the data from about 15 million social media check-in records during a year-long period in Shanghai, China. We identified a series of latent structures, named latent spatio-temporal activity structures. While interpreting these structures, we can obtain a series of underlying associations between the spatial and temporal activity patterns. Moreover, we can not only reproduce the observed data with a lower dimensional representative, but also project spatio-temporal activity patterns in the same coordinate system. With the K-means clustering algorithm, five significant types of clusters that are directly annotated with a combination of temporal activities can be obtained, providing a clear picture of the correlation between the groups of regions and different activities at different times during a day. Besides the commercial and transportation dominant areas, we also detected two kinds of residential areas, the developed residential areas and the developing residential areas.We further interpret the spatial distribution of these clusters using urban form analytics. The results are highly consistent with the government planning in the same periods, indicating that our model is applicable to infer the functional regions from social media check-in data and can benefit a wide range of fields, such as urban planning, public services, and location-based recommender systems.展开更多
基金supported by grants from the National Nature Science Foundation of China(30872666,81172911 and 81271379)Shanghai Key Lab of Forensic Medicine(KF1005)
文摘Objective To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P 1 component （peak latency -100 ms） of the pattern-reversal visual-evoked potential （PRVEP） and the visual acuity at particular visual angles. Methods Two hundred and ten volunteers were divided into seven groups, according to visual acuity as assessed by the standard logarithmic visual acuity chart （SLD-II）. For each group, the PRVEP components were elicited in response to visual angle presentations at 8°, 4°, 2°, 1°/60＇, 30＇, 15＇, and 7.5＇, in the whiteblack chess-board reversal mode with a contrast level of 100% at a frequency of 2 Hz. Visual stimuli were presented monocularly, and 200 presentations were averaged for each block of trials. The early and stable component P1 was recorded at the mid-line of the occipital region （Oz） and analyzed with SPSS 13.00. Results （1） Oz had the maximum Pl amplitude; there was no significant difference between genders or for interocular comparison in normal controls and subjects with optic myopia. （2） The P1 latency decreased slowly below 30＇, then increased rapidly. The P1 amplitude initially increased with check size, and was maximal at -1° and -30＇. （3） The P1 latency in the group with visual acuity 〈0.2 was signifi- cantly different at 8°, 15＇ and 7.5＇, while the amplitude differed at all visual angles, compared with the group with normal vision. Differences in P1 for the groups with 0.5 and 0.6 acuity were only present at visual angles 〈1°. （4） Regression analysis showed that the P1 latency and amplitude were associated with visual acuity over the full range of visual angles. There was a moderate correlation at visual angles 〈30＇. Regression equations were calculated for the P1 components and visual acuity, based on visual angle. Conclusion （1） Visual angle should be taken into consideration when exploring the function of the visual pathway, especially visual acuity. A visual angle -60＇ might be appropriate when using PRVEP com- ponents to evaluate poor vision and to identify malingerers. （2） Increased P1 amplitude and decreased P1 latency were as- sociated with increasing visual acuity, and the P1 components displayed a linear correlation with visual acuity, especially in the range of optimal visual angles. Visual acuity can be deduced from P 1 based on visual angle.
文摘In exterior use, wood is subjected to weathering that causes checking and other deterioration in the appearance and technical properties. We studied quantitatively the surface checking of radially and tangentially sawn specimens of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies Karst.) wood in a cyclic climate chamber test. The results strongly suggested that the sawing direction determines the checking performance of both Scots pine and Norway spruce wood. The radial surface of Scots pine specimens had 62% less checks than the tangential one, and the cumulative area of checks was 74% smaller. For Norway spruce, the respective figures were: 83% less in the check number and 91% less in the check area. Different from pine, in spruce specimens the checks of radial surface were significantly smaller. Thus, spruce timber gained clearly more about radial sawing pattern. The effect of annual ring width was similar for pine and spruce: the reduction in annual growth worsened the checking. The increase in density worsened the checking of spruce but did not change the performance of pine. In pine wood, the increase of heartwood proportion reduced the fluctuation of moisture content and the formation of checks.
基金the Open Research Fund Program of Shenzhen Key Laboratory of Spatial Smart Sensing and Services%sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry(grant number 50-20150618)%National Natural Science Foundation of China (grant numbers 41001220, 51378512, 41571397, and 41501442)This work was also supported by the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund
文摘This article introduces a novel low rank approximation (LRA)-based model to detect the functional regions with the data from about 15 million social media check-in records during a year-long period in Shanghai, China. We identified a series of latent structures, named latent spatio-temporal activity structures. While interpreting these structures, we can obtain a series of underlying associations between the spatial and temporal activity patterns. Moreover, we can not only reproduce the observed data with a lower dimensional representative, but also project spatio-temporal activity patterns in the same coordinate system. With the K-means clustering algorithm, five significant types of clusters that are directly annotated with a combination of temporal activities can be obtained, providing a clear picture of the correlation between the groups of regions and different activities at different times during a day. Besides the commercial and transportation dominant areas, we also detected two kinds of residential areas, the developed residential areas and the developing residential areas.We further interpret the spatial distribution of these clusters using urban form analytics. The results are highly consistent with the government planning in the same periods, indicating that our model is applicable to infer the functional regions from social media check-in data and can benefit a wide range of fields, such as urban planning, public services, and location-based recommender systems.
