Satellite-driven downscaling of global reanalysis precipitation products for hydrological applications

Deriving flood hazard maps for ungauged basins typically requires simulating a long record of annual maximum discharges. To improve this approach, precipitation from global reanalysis systems must be downscaled to a spatial and temporal resolution applicable for flood modeling. This study evaluates such downscaling and error correction approaches for improving hydrologic applications using a combination of NASA's Global Land Data Assimilation System (GLDAS) precipitation data set and a higher resolution multi-satellite precipitation product (TRMM). The study focuses on 437 flood-inducing storm events that occurred over a period of ten years (2002–2011) in the Susquehanna River basin located in the northeastern United States. A validation strategy was devised for assessing error metrics in rainfall and simulated runoff as function of basin area, storm severity, and season. The WSR-88D gauge-adjusted radar-rainfall (stage IV) product was used as the reference rainfall data set, while runoff simulations forced with the stage IV precipitation data set were considered as the runoff reference. Results show that the generated rainfall ensembles from the downscaled reanalysis product encapsulate the reference rainfall. The statistical analysis consists of frequency and quantile plots plus mean relative error and root-mean-square error statistics. The results demonstrated improvements in the precipitation and runoff simulation error statistics of the satellite-driven downscaled reanalysis data set compared to the original reanalysis precipitation product. Results vary by season and less by basin scale. In the fall season specifically, the downscaled product has 3 times lower mean relative error than the original product; this ratio increases to 4 times for the simulated runoff values. The proposed downscaling scheme is modular in design and can be applied on any gridded satellite and reanalysis data set

The Effect of Immediate and Delayed Error Correction on Accuracy Development of Intermediate EFL Learners’ Writing

This study investigated the immediate and delayed effects of error correction on the accuracy improvement of intermediate EFL learners’ writing. Through TOEFL test, the researcher selected 3 intact intermediate classes and assigned them into peer correction, self-correction and teacher correction groups. Before the main treatment, all participants were requested to write a composition on a topic, which served the purpose of pre-test. After writing the composition, the first group (peer), including two learners in each group, corrected the errors underlined by the teacher together. The learners in the second group, namely, self-correction, corrected the errors underlined by teacher individually and the third group received the correct forms written by the teacher on top of the errors. All the groups wrote 6 compositions on the topics during 6 sessions. The first topic served the purpose of immediate pre-test. This procedure was followed for 6 weeks and the 6th composition was regarded as immediate post-test and after a month (12th week), delayed post-test was conducted for all learners. The findings of ANOVA indicated that both peer correction and selfcorrection were influential in enhancing learners' writing accuracy; however, the group doing peer correction outperformed the self-correction one

Ап Efficient data hiding Scheme Using Discrete Wavelet Transform

Information hiding based on digital images is still the mainstream now. This article represents a new hiding method based on propability of block in frequency domain, we apply discrete wavelet transform through lifting scheme on cover image then divided subband LH to nun overloaping blocks. Each bit of secret message embedded in cover image with modified entensity value of each block. Experimental results demonstrate that the proposed scheme is robust to common image processing attack like filtering, image compression attack and addaptive noise

Ап Efficient data hiding Scheme Using Discrete Wavelet Transform

Information hiding based on digital images is still the mainstream now. This article represents a new hiding method based on propability of block in frequency domain, we apply discrete wavelet transform through lifting scheme on cover image then divided subband LH to nun overloaping blocks. Each bit of secret message embedded in cover image with modified entensity value of each block. Experimental results demonstrate that the proposed scheme is robust to common image processing attack like filtering, image compression attack and addaptive noise

A Novel Secure Steganographic Method Based on Zero Tree Method

A secure steganographic method is proposed for embedding secret messages into gray scale images in frequency domain based on partitioning approach. The cover image is divided into 8×8 non-overlapping blocks and integer wavelet transform through lifting scheme is performed for each block. In order to find proper location for embedding secret message, the zero tree method is applied to each block. The lossless data compression encoding applied to secret message to obtain high secrecy, high payload and authentication. Secret message embedded in cover image without degrading the quality of the original image. Simulation result reveals that, the proposed method has achieved better performance in terms of high data embedding payload, high imperceptibility of stego-image and secure against statistical attack compared with existing methods

An Adaptive Steganographic Method in Frequency Domain Based on Statistical Metrics of Image

Steganography is a branch of information hiding. A tradeoff between the hiding payload and quality of digital image steganographic schemes is major challenge of the steganographic methods. An adaptive steganographic method for embedding secret message into gray scale images is proposed. Before embedding the secret message, the cover image is transformed into frequency domain by integer wavelet. The middle frequency band of cover image is partitioned into 4×4 non overlapping blocks. The blocks by deviation and entropy metrics are classified into three categories: smooth, edge, and texture regions. Number of bits which can be embedded in a block is defined by block features. Moreover, RC4 encryption method is used to increase secrecy protection. Experimental results denote the feasibility of the proposed method. Statistical tests were conducted to collect related data to verify the security of method