可充电无人机辅助数据采集系统的飞行路线与通信调度优化

考虑一个可充电无人机辅助的无线传感器网络,网络包含多个地面终端,每个终端需要传输大量具有时间敏感性的数据。由于电池容量有限,无人机无法通过单次飞行任务采集全部终端的数据,它需要多次返回充电桩补充能量。研究了无人机的终端调度、飞行轨迹、飞行速度与传输速率优化,在数据生命期内最大化采集的终端数量。变量之间高度耦合且存在离散的二进制变量,涉及的优化问题难以求解,故而提出基于随机优化和特征工程思想的算法求解该优化问题。首先,引入飞行—悬停通信协议降低轨迹优化的复杂度,然后创新性地提出基于影响因子和随机优选的通信调度算法。该算法通过提取终端上影响无人机服务时间的特征赋予终端优先级,计算出不同终端服务总数下的最优调度方案,从而把优化问题简化成多个求解最短耗时的子问题,并利用块坐标下降法和连续凸近似技术求得子问题的解。仿真结果表明,与几种基准策略相比,所提优化算法在不同数据生命期与不同请求服务终端总数的场景下都有显著的性能优势。

数据安全审计方法与实施探索

本文依据数据安全能力成熟度模型等标准规范,设计涵盖数据安全治理、数据安全管理、数据生命期安全管理、数据平台技术及专题审计等方面的数据安全审计框架。依据数据安全审计框架,对数据安全审计的内容和程序进行描述,为开展数据安全审计工作提供参考与借鉴。

A Data Assured Deletion Scheme in Cloud Storage

In order to provide a practicable solution to data confidentiality in cloud storage service,a data assured deletion scheme,which achieves the fine grained access control,hopping and sniffing attacks resistance,data dynamics and deduplication,is proposed.In our scheme,data blocks are encrypted by a two-level encryption approach,in which the control keys are generated from a key derivation tree,encrypted by an All-OrNothing algorithm and then distributed into DHT network after being partitioned by secret sharing.This guarantees that only authorized users can recover the control keys and then decrypt the outsourced data in an ownerspecified data lifetime.Besides confidentiality,data dynamics and deduplication are also achieved separately by adjustment of key derivation tree and convergent encryption.The analysis and experimental results show that our scheme can satisfy its security goal and perform the assured deletion with low cost.

Modeling Digital Evidence Management and Dynamics Using Petri Nets

In all phases of forensic investigation, digital evidence is exposed to external influences and coming into contact with many factors. Legal admissibility of digital evidence is the ability of that evidence being accepted as evidence in a court of law. Life cycle of digital evidence is very complex. In each stage there is more impact that can violate a chain of custody and its integrity. Contact with different variables occurs through a life cycle of digital evidence and can disrupt its integrity. In order for the evidence to be accepted by the court as valid, chain of custody for digital evidence must be kept, or it must be known who exactly came into contact with evidence in each stage of the investigation. This paper presents a dynamics and life cycle of digital evidence. The Petri nets will be proposed and used for modeling and simulation of this process.

A Matrix-Based Approach for Sustainability in Product Design

The paper proposes a matrix-based approach that a designer can use to evaluate the sustainability of one or more design solutions in the conceptual phase of a product development process. The methodology is structured in two main phases. In the first one, a data structure, called Augmented-DSM （Design Structure Matrix）, has to be drawn in order to collect design information such as functional links among product components, indicators that provide information about the life cycle of each element, connections with the environment and toward other systems. The matrix is based on a DSM format, where new records were introduced to store and organize different types of data and an editing protocol was formalized. In the second stage, a set of procedures have to be applied in order to evaluate sustainability of a design solution and compare it with the others. The presented procedures, in fact, allow designers to assess a product in its proper characteristics, evaluate a device during its use stage and verify the coherence of links present in the functional model. This new approach is conceived to manage different performance indicators and, as a support tool, it is an attempt to aid designers in a quantitative evaluation.

Debt Rating Initiations： Natural Evolution or Opportunistic Behavior？

The authors examine a firm＇s decision to begin issuing debt in public bond markets and find that it is a function of both life cycle influences and opportunistic timing. Defining life cycle factors to encompass both a firm＇s age in years and its underlying characteristics, the authors confirm that bond market participation is generally restricted to large, mature firms. Summary statistics show that finns obtain their initial bond ratings on average 9.5 years after their equity initial public offering （IPO） and 11.8 years after initiating dividend payments. Growth rates, capital expenditures, and cash flow volatility all decline as the firm accesses public debt markets, consistent with entry into the mature phase of its life cycle. With respect to opportunistic timing, it is asked whether entry into public bond markets follows strong performance （or precedes weak performance） at both the firm and market levels. At the firm level, the authors find that the debt IPO occurs following periods of strong operating performance and high excess stock returns. At the market level, entry coincides with favorable interest rates and default spreads. The benefits of careful timing result in firms receiving initial bond ratings that are stronger than what would be predicted; however, there is no evidence of abnormal numbers of downgrades for these firms in subsequent years.

Usage of 3D Point Cloud Data in BIM （Building Information Modelling）： Current Applications and Challenges

BIM （building information modelling） has gained wider acceptance in the A/E/C （architecture/engineering/construction） industry in the US and internationally. This paper presents current industry approaches of implementing 3D point cloud data in BIM and VDC （virtual design and construction） applications during various stages of a project life cycle and the challenges associated with processing the huge amount of 3D point cloud data. Conversion from discrete 3D point cloud raster data to geometric/vector BIM data remains to be a labor-intensive process. The needs for intelligent geometric feature detection/reconstruction algorithms for automated point cloud processing and issues related to data management are discussed. This paper also presents an innovative approach for integrating 3D point cloud data with BIM to efficiently augment built environment design, construction and management.

Comparative Analysis of Energy Efficiency in Wheat Production in Different Climate Conditions of Europe

This paper presents results concerning energy efficiency of wheat production considered in the context of specific energy input variation in different climatic conditions of Europe as well as case studies on implementation of selected energy saving measures in practice. The source data collected from the six european union （EU） countries represent five agricultural regions of continental Europe and three climates： continental, temperate and Mediterranean. The life cycle assessment （LCA） methodology was applied to analyze the data excluding of pre-farm gate activities. The total primary energy consumption was decomposed into main energy input streams and it was regressed to yield. In order to compare energy efficiency of wheat production across the geographical areas, the data envelopment analysis （DEA） was applied. It was shown that the highest wheat yield （6.7 t/ha to 8.7 t/ha） at the lowest specific energy input （2.08 GJ/t to 2.56 G J/t） is unique for temperate climate conditions. The yield in continental and Mediterranean climatic conditions is on average lower by 1.3 t/ha and 2.7 t/ha and energy efficiency lower by 14% and 38%, respectively. The case studies have shown that the energy saving activities in wheat production may be universal for the climatic zones or specific for a given geographical location. It was stated that trade-offs between energy, economic, and environmental effects, which are associated with implementation of a given energy saving measure or a set of measures to a great extent depend on the current energy efficiency status of the farm and opportunity for investment, which varies substantially across Europe.

Estimating the Service Lives of Building Products in Use

Reliable service life data of building products are of great importance when completing environmental LCA （life cycle assessment） reviews, for LCC （life cycle costing） and for maintenance planning tasks. A research project was set up to answer the following research questions： （1） what are reliable service life data of current used building products; and （2） how can generic data about the service lives of building products be tailored to specific project circumstances using the ＂factor method＂ described in the ISO （International Standard Organization） 15686 Series： ＂Buildings and Constructed Assets-Service-Life Planning＂. Experts of industry organisations for building materials and products made a final judgement of the new established reference service lives. Reference service lives of building products may show a large unknown bandwidth around the average. That will make the bandwidth of estimated service lives, taking the project situation of building components into account, very big. Experts have raised objections to the use the factor method for deriving mathematically a bandwidth of estimated service lives of a building product from the reference service life of the product. A practical analytical application of the factor method has been made by describing all factors and underlying criteria and a reference situation.