Bilinear Random Projections for Locality-Sensitive Binary Codes

Locality-sensitive hashing (LSH) is a popular data-independent indexing method for approximate similarity search, where random projections followed by quantization hash the points from the database so as to ensure that the probability of collision is much higher for objects that are close to each other than for those that are far apart. Most of high-dimensional visual descriptors for images exhibit a natural matrix structure. When visual descriptors are represented by high-dimensional feature vectors and long binary codes are assigned, a random projection matrix requires expensive complexities in both space and time. In this paper we analyze a bilinear random projection method where feature matrices are transformed to binary codes by two smaller random projection matrices. We base our theoretical analysis on extending Raginsky and Lazebnik's result where random Fourier features are composed with random binary quantizers to form locality sensitive binary codes. To this end, we answer the following two questions: (1) whether a bilinear random projection also yields similarity-preserving binary codes; (2) whether a bilinear random projection yields performance gain or loss, compared to a large linear projection. Regarding the first question, we present upper and lower bounds on the expected Hamming distance between binary codes produced by bilinear random projections. In regards to the second question, we analyze the upper and lower bounds on covariance between two bits of binary codes, showing that the correlation between two bits is small. Numerical experiments on MNIST and Flickr45K datasets confirm the validity of our method.Comment: 11 pages, 23 figures, CVPR-201

Are master plans effective in limiting development in China's disaster-prone areas?

The effectiveness of urban master plans in limiting development in a disaster-prone area of China was empirically investigated by measuring cities’ land-cover changes against their master plans. If a master plan serves as guidance for urban polices that reduce property loss from earthquakes, floods, landslides,land subsidence, and rises in sea level, it will substantially limit urban development in areas at risk from environmental hazards. An environmental risk map weighted toward valuable forms of land cover was generated using geospatial databases of China’s Yangtze River Delta region. Based on this data, the effects of five master plan measures—ring-road patterns, block size, the area of urban built-up lands, the locations of industrial sites, and preservation zoning—were tested using the multiple regression method. Cities showing a high degree of compliance, in particular with preservation zoning, had a smaller amountof urban land located in high-risk zones, on average, by 14 km2. Among the top ten cities exposed to disproportionately high risks, eight were towns and only two were cities like Huzhou and Kunshan

Does large-sized cities' urbanisation predominantly degrade environmental resources in China? Relationships between urbanisation and resources in Changjiang Delta Region

Outward expansion of urban lands in the developing nations is often associated with a substantial loss of environmental resources such as forests, wetlands, freshwater and cash crop fields. Yet, determining how different aspects of urbanisation – such as city population size and spread pattern of built-up lands – contribute to the cumulative loss of resources remains controversial. In this study, data sets were constructed describing changes to land cover across 65,200 grid cells at 1 km2 spatial resolution for China’s Changjiang Delta Region over the past 60 years. The results showed that the region lost 12.2% of total resource sites. The distribution of resource degradation showed a highly dispersed pattern and was not confined to a few intense areas associated with large cities. No empirical evidence was found that city population size alone accurately predicts the distribution of resource loss. Very large cities (N = 4) contributed 35% to the total loss, demonstrating impacts similar to those of much more scattered towns (N = 230). Urban expansion of large cities may lead to extensive resource loss; however, a set of non-linear mechanisms, such as the diminishing effects of per-unit area urban spread on resources and interactions between urban patterns and the size of urban spread, can also play a significant role in downsizing the negative effects of large cities on resource sites. Thus, effective urban policies should carefully weigh the cumulative urban spread mechanisms of both large and small cities responsible for spatially dispersed degradation of environmental resources

Investigating the effect of a raised cycle track, physical separation, land use and number of pedestrian on cyclists’ gaze behavior

Contemporary cities are home to an increasing number of cyclists. The gaze behavior of cyclists has an important impact upon cyclist safety and experience. Yet this behavior has not been studied to access its potential implications for urban design. This study aims to identify the eye-gaze pattern of cyclists and to examine its potential relationships with urban environmental characteristics, such as a raised cycle track, physical separation, land use, and number of pedestrian. This study measured and analyzed 40 cyclist’s gaze patterns using an eye tracker; the results were as follows. First, cyclists presented a T-shaped gaze pattern with two spots of frequent eye fixation points; the pattern suggests that it may benefit cyclists with greater safety and better readiness of road situation to avoid crashes. Second, more active horizontal gaze dispersion within the T-shaped gaze pattern was observed when participants cycled on a shared and non-raised bikeway. This indicates that there is a more suitable gaze behavior with different gaze limitations depending on the environmental characteristics. Therefore, bicycle facilities need to be constructed according to the consideration of the T-shaped gaze area and the change in cyclists’ gaze behavior in each environment to increase the effectiveness of bicycle facilities