Drive laser system for the DC-SRF photoinjector at Peking University

Photoinjectors are widely used for linear accelerators as electron sources to generate high-brightness electron beam. Drive laser, which determines the timing structure and quality of the electron beam, is a crucial device of photoinjector. A new drive laser system has been designed and constructed for the upgraded 3.5-cell DC-SRF photoinjector at Peking University. The drive laser system consists of a 1064 nm laser oscillator, a four- stage amplifier, the second and fourth harmonic generators, the optical system to transfer the UV pulses to the photocathode, and the synchronization system. The drive laser system has been successfully applied in the stable operation of DC-SRF photoinjector and its performance meets the requirements. 266 nm laser with an average power close to 1W can be delivered to illuminate the Cs2Te photocathode and the instability is less than 5% for long time operation. The design consideration for improving the UV laser quality, a detailed description of laser system, and its performance are presented in this paper.Comment: 6 pages, 8 figures, submit to CP

Resource-Efficient Cooperative Online Scalar Field Mapping via Distributed Sparse Gaussian Process Regression

Cooperative online scalar field mapping is an important task for multi-robot systems. Gaussian process regression is widely used to construct a map that represents spatial information with confidence intervals. However, it is difficult to handle cooperative online mapping tasks because of its high computation and communication costs. This letter proposes a resource-efficient cooperative online field mapping method via distributed sparse Gaussian process regression. A novel distributed online Gaussian process evaluation method is developed such that robots can cooperatively evaluate and find observations of sufficient global utility to reduce computation. The bounded errors of distributed aggregation results are guaranteed theoretically, and the performances of the proposed algorithms are validated by real online light field mapping experiments

Reason Analysis on the Variation of Reservoir Thickness Interpretation of Different Logging Series in Sanan Development Zone

In the oilfield development process, for the geological problems, the new logging apparatus has been developed and the logging series are constantly changing. Comparing the thickness interpretation of different logging series, this paper has analyzed the variation reasons of the thickness and the effect factors of thickness interpretation such as well logging series, mud properties, formation pressure, formation fluid properties and well spacing density. This provides a more reliable parameter for calculating oil geological reserves accurately and improving reservoir evaluation.Key words: Logging series; Reservoir; Thickness division; Effective thicknes

Gender and Grade Differences in Knowledge and Behaviors Related to Active Living for Adolescents

The purpose of this study was to examine differences by gender and grade in middle school students’ physical activity and fitness (PAF) knowledge, physical activity, and sedentary behavior (SB). The study took place at one middle school located in the Southeastern region of the United States. Boys (n = 136) and girls (n = 166) in 6th (n =129), 7th (n = 96) and 8th (n = 77) completed a PE Metrics written test to assess PAF knowledge. They (N = 312) also completed the validated Youth Activity Profile to report physical activity at school (PAS), physical activity at home (PAH), and SB. Two-way (gender by grade) multivariate analysis of variances (MANOVA) followed by Bonferroni post-hoc multiple comparison analysis were conducted. Box’s M test of covariance matrices showed no statistical violation (M = 37.78, F = .73, p \u3e .05). The two-way MANOVA showed significant gender (Wilks’s λ = .94, F = 4.40, p \u3c .01, N(2/p) \u3c .06) and grade main effects (Wilks’s λ = .89, F = 4.20, p \u3c .01, N(2/p) \u3c .05). No significant gender by grade interaction effect was detected (p \u3e .05). Subsequent tests of between subjects effect located the significant gender difference in PAS favoring boys (F = 9.3, p \u3c .01, N(2/p) = .03). Boys and girls showed no significant difference on PAF knowledge, PAH, and SB. Significant grade differences were observed for PAS (F = 8.57, p \u3c .01, N(2/p) =.06), PAH (F = 8.18, p \u3c .01, N(2/p) =.05), and SB (F = 4.61, p = .01, N(2/p) \u3e = .03). Sixth grade students showed significantly higher levels of PAS and PAH than 7th and 8th grade students (p \u3c .05 or \u3c .01). Sixth grade students further showed significantly lower SB than 7th grade students (p \u3c .05). This study found boys to be more physically active during school hours than girls, and students in lower grades to be more active than higher grade students. Future school-based interventions should take into account gender and grade-based differences