环境经济系统工程的思考

环境问题与经济问题紧密相连,由于环境问题的综合性和复杂性,需要运用系统工程的方法和经济学原理,将环境问题置于整个经济系统中统筹考虑,建立相对完整的环境经济系统工程方法体系,将环境保护工作纳入经济社会发展中,使其成为决策中主要考虑的因素之一,并引起应有的重视。本研究从环境与经济承载力、环境投资的经济分析、环境与投资效率比较、环境资源的经济价值以及生态补偿与污染赔偿等方面构建环境经济系统工程的基本框架体系,并结合实际进行案例分析。研究表明,单纯的政府行政干预不如创造条件,如补偿、税收减免、投资、贴息等,使其具备在市场规则下.自动引导资源向环境保护与污染治理的投入,如排污指标的交易等。此外,自然资源是不可或缺的稀有资本,应该将保护生态系统及生物多样性纳入各级政府决策的主要方面。     

A modular designed bolt tightening shaft based on adaptive fuzzy backstepping control

This paper presents a modular designed autonomous bolt tightening shaft system with an adaptive fuzzy backstepping control approach developed for it. The bolt tightening shaft is designed for the autonomous bolt tightening operation, which has huge potential for industry application. Due to the inherent nonlinear and uncertain properties, the bolt tightening shaft and the bolt tightening process are mathematically modeled as an uncertain strict feedback system. With the adaptive backstepping and approximation property of fuzzy logic system, the controller is recursively designed. Based on the Lyapunov stability theorem, all signals in the closed-loop system are proved to be uniformly ultimately bounded and the torque tracking error exponentially converges to a small residue. And the effectiveness and performance of the proposed autonomous system are verified by the simulation and experiment results on the bolt tightening shaft system.     

Practical chosen-ciphertext secure Hierarchical Identity-Based Broadcast Encryption

We focus on practical Hierarchical Identity-Based Broadcast Encryption (HIBBE) with semantic security against adaptively chosen-ciphertext attacks (CCA2) in the standard model. We achieve this goal in two steps. First, we propose a new HIBBE scheme that is secure against chosen-plaintext attacks (CPA). Compared with the existing HIBBE scheme that is built from composite-order bilinear groups, our construction is based on prime-order bilinear groups. The much better efficiency of group operations in prime-order bilinear groups makes our proposed HIBBE scheme more practical. Then, we convert it into a CCA2-secure scheme at the cost of a one-time signature. Instead of extending one user hierarchy in the Canetti–Halevi–Katz approach from CPA-secure (\(l+1\))-Hierarchical Identity-Based Encryption [(\(l+1\))-HIBE] to CCA2-secure \(l\)-HIBE, our construction merely adds one on-the-fly dummy user in the basic scheme. We formally prove the security of these two schemes in the standard model. Comprehensive theoretical analyses and experimental results demonstrate that the proposed HIBBE schemes achieve desirable performance.