区块链分片技术综述

区块链作为分布式账本的关键技术之一,其去中心化、可匿名、不可篡改的特性受到学术界和工业界的青睐,被广泛应用于金融、数字货币、公共服务等领域。分片技术作为区块链扩容的主流方式之一,能够在不降低区块链去中心化程度的同时实现高性能的链上扩容,从而解决区块链可拓展性不足以及吞吐量较低的问题。介绍近年来出现的分片技术以及相关协议,总结分片技术的关键理论与方法,从分片配置、重配置、片内共识协议、跨片共识协议、状态存储等方面对分片技术方案进行对比,归纳不同分片方案在网络分片、交易分片、状态分片等设计中存在的优势和不足。同时,阐述一些经典分片技术在性能和实现方式上的特点,对许可区块链和无许可区块链、片内共识协议、跨片共识协议、准入性方案、状态分片方式等进行分析和概述。在此基础上,从分片内、分片间以及系统层级的角度总结分片技术当前所面临的困境和挑战,并对该领域的发展前景及未来研究方向加以展望。     

区块链+物联网在农产品溯源中的应用研究

近年来,农产品安全问题日益严峻,传统的农产品追溯体系面临公信力缺失、监管困境和扩展性问题,农产品质量安全追溯迫在眉睫。随着区块链技术不断发展,其具有的分布式、去中心化、不可篡改、可追溯等特性在改善农产品溯源系统数据安全性、透明性等方面发挥着重要作用,并受到了各个行业的广泛关注。在简述可追溯性和追溯系统概念的基础上,介绍物联网和区块链技术,并探讨了当前国内外学者将区块链和物联网框架融合应用到农产品溯源中的一些相关研究,同时阐述了溯源系统在物联网与区块链结合下带来的安全、可靠、透明等好处及面临可扩展性、效率问题、资源浪费等挑战,最后对当前农产品溯源体系建设提出建议以及未来的研究方向。     

Remote sensing of soil salinity: potentials and constraints

Soil salinity caused by natural or human-induced processes is a major environmental hazard. The global extent of primary salt-affected soils is about 955 M ha, while secondary salinization affects some 77 M ha, with 58% of these in irrigated areas. Nearly 20% of all irrigated land is salt-affected, and this proportion tends to increase in spite of considerable efforts dedicated to land reclamation. This requires careful monitoring of the soil salinity status and variation to curb degradation trends, and secure sustainable land use and management. Multitemporal optical and microwave remote sensing can significantly contribute to detecting temporal changes of salt-related surface features. Airborne geophysics and ground-based electromagnetic induction meters, combined with ground data, have shown potential for mapping depth of salinity occurrence. This paper reviews various sensors (e.g. aerial photographs, satellite- and airborne multispectral sensors, microwave sensors, video imagery, airborne geophysics, hyperspectral sensors, and electromagnetic induction meters) and approaches used for remote identification and mapping of salt-affected areas. Constraints on the use of remote sensing data for mapping salt-affected areas are shown related to the spectral behaviour of salt types, spatial distribution of salts on the terrain surface, temporal changes on salinity, interference of vegetation, and spectral confusions with other terrain surfaces.As raw remote sensing data need substantial transformation for proper feature recognition and mapping, techniques such as spectral unmixing, maximum likelihood classification, fuzzy classification, band ratioing, principal components analysis, and correlation equations are discussed. Lastly, the paper presents modelling of temporal and spatial changes of salinity using combined approaches that incorporate different data fusion and data integration techniques.     

Integration | Innovation | Inclusion: Values,Variables and the Design of Human Environments

Complexity, complication, contradiction, consumption, confusion, delusion, depression. Opportunity, inspiration, ingenuity, compassion, wisdom. Our world is perplexing, our times are fast moving, and our choices are many. To find an appropriate path is a daunting yet vital challenge that confronts us as individuals, as communities, and as a civilization. How sustainable is our world? How reasonable are our behaviors? The present article is a collection of thoughts on a series of intertwined issues related to the contemporary world, its environmental dimensions, and their present-day problems. The goal is to survey the landscape through a lens of Environmental Design, to provide some perspectives, to raise some questions, and to explore systems, beliefs, and values informing and influencing actions. It is important to consider how people's belief systems influence, inform, and shape actions. This holds true in realms political, spiritual, and cultural. It also proves relevant in the ways in which we imagine, design, develop, and construct our buildings, cities, spaces, and places.

Appropriate solutions to some of our most daunting problems will arise through the concerted efforts, open dialogue, and collective wisdom of the wide array of stakeholders, professionals, politicians, decision makers, and citizens (both engaged and disenfranchised) who have the will and wherewithal to make a difference and to make the world safer, healthier, and better. It seems vital for us to critically examine, and question, our belief systems and their connections to the ways we define, refine, and realize progress. Architecture and Environmental Design, in both a philosophical and a practical sense, reflect as well as form greater aspirations, directions, and events of our times.     

分布式地学虚拟环境研究

讨论了分布式地学虚拟环境的概念,特征以及与GIS的相互关系,从系统结构,数据模型,交互界面和开发工具方面,对分布式地学虚拟环境的系统框架进行了研讨。最后,从理论,技术和应用层面介绍了关于分布式地学虚拟环境的研究热点和难点,并讨论了进一步的研究方向。     

Expert system verification and validation: a survey and tutorial

Assuring the quality of an expert system is critical. A poor quality system may make costly errors resulting in considerable damage to the user or owner of the system, such as financial loss or human suffering. Hence verification and validation, methods and techniques aimed at ensuring quality, are fundamentally important. This paper surveys the issues, methods and techniques for verifying and validating expert systems. Approaches to defining the quality of a system are discussed, drawing upon work in both computing and the model building disciplines, which leads to definitions of verification and validation and the associated concepts of credibility, assessment and evaluation. An approach to verification based upon the detection of anomalies is presented, and related to the concepts of consistency, completeness, correctness and redundancy. Automated tools for expert system verification are reviewed. Considerable attention is then given to the issues in structuring the validation process, particularly the establishment of the criteria by which the system is judged, the need to maintain objectivity, and the concept of reliability. This is followed by a review of validation methods for validating both the components of a system and the system as a whole, and includes examples of some useful statistical methods. Management of the verification and validation process is then considered, and it is seen that the location of methods for verification and validation in the development life-cycle is of prime importance.     

面向大尺寸货物运送的吊车控制方法综述

随着现代化工业和基础设施建设的飞速发展,面向大尺寸货物运送的吊车系统以其高负载能力、低成本的显著优势广泛应用于集装箱搬运、风机安装、飞机机翼机身移动、水轮发电机转子安装、海上钻井平台搭建等诸多重要领域。然而,相对于传统的点质量单摆吊车系统,面向大尺寸货物运送的吊车系统具有更高的欠驱动程度、更强的状态耦合性和更加复杂的非线性,给大尺寸货物高效、安全的运送控制带来严峻挑战。本文首先简单阐述了面向大尺寸货物运送吊车系统不同吊装形式的建模、优势和缺点;然后,详细介绍了点质量双摆吊车系统、分布式质量双摆吊车系统和多吊车协同运送系统控制的研究现状;最后,对面向大尺寸货物运送吊车系统控制的研究现状进行概括,并对可能存在的关键问题和未来的研究方向进行了讨论和展望。     

Survival analysis of a neotropical rainforest using multitemporal satellite imagery

We present results of an analysis of deforestation at a UNESCO Biosphere Reserve, the Parque National Yasuní, located in the rainforests of eastern Ecuador using multitemporal Landsat TM and ETM+ satellite imagery. Using survival analysis, we assessed both current and future trends in deforestation rates, and investigated the impact of spatial, cultural, and economic factors on deforestation. These factors included the distance from roads, rivers, research facilities, oil facilities, markets and towns, and land ownership by colonists, native inhabitants, and an oil company. We found the annual rate of deforestation is currently only 0.11%, but that this rate is increasing with time and, assuming that the trend of increasing rate of forest loss continues, we would predict that by 2063, 50% of the forest within 2 km of an oil access road will be lost to unhindered colonization and anthropogenic conversion. The Quechua colonists are associated with areas of the highest rate of deforestation, followed by the native Huaorani and the lowest region of deforestation was in areas occupied by a local oil company. By far, the strongest predictor of where deforestation is predicted to occur was proximity to the road. Proximity to research sites, oil facilities, market, and rivers significantly decreases deforestation rates, and proximity to towns significantly increases deforestation rates.     

Calibration of the SLEUTH urban growth model for Lisbon and Porto, Portugal

The SLEUTH model (slope, landuse, exclusion, urban extent, transportation and hillshade), formerly called the Clarke Cellular Automaton Urban Growth Model, was developed for and tested on various cities in North America, including Washington, DC, and San Francisco. In contrast, this research calibrated the SLEUTH model for two European cities, the Portuguese metropolitan areas of Lisbon and Porto. The SLEUTH model is a cellular automaton model, developed with predefined growth rules applied spatially to gridded maps of the cities in a set of nested loops, and was designed to be both scaleable and universally applicable. Urban expansion is modeled in a modified two-dimensional regular grid. Maps of topographic slope, land use, exclusions, urban extents, road transportation, and a graphic hillshade layer form the model input. This paper examines differences in the model's behavior when the obviously different environment of a European city is captured in the data and modeled. Calibration results are included and interpreted in the context of the two cities, and an evaluation of the model's portability and universality of application is made. Questions such as scalability, sequential multistage optimization by automated exploration of model parameter space, the problem of equifinality, and parameter sensitivity to local conditions are explored. The metropolitan areas present very different spatial and developmental characteristics. The Lisbon Metropolitan Area (the capital of Portugal) has a mix of north Atlantic and south Mediterranean influences. Property is organized in large patches of extensive farmland comprised of olive and cork orchards. The urban pattern of Lisbon and its environs is characterized by rapid urban sprawl, focused in the urban centers of Lisbon, Oeiras, Cascais Setúbal, and Almada, and by intense urbanization along the main road and train lines radiating from the major urban centers. The Porto Metropolitan Area is characterized by a coastal Atlantic landscape. The urban pattern is concentrated among the main nuclei (Porto and Vila Nova de Gaia) and scattered among many small rural towns and villages. There are very small isolated patches of intensive agriculture and pine forests in a topography of steep slopes. These endogenous territorial characteristics go back in time to the formation of Portugal — with a “Roman-Visigod North” and an “Arabic South” [Firmino, 1999 (Firmino, A., 1999. Agriculture and landscape in portugal. Landscape and Urban planning, 46, 83–91); Ribeiro, Lautensach, & Daveau, 1991 (Ribeiro, O., Lautensach, H., & Daveau, S., 1991. Geografia de portugal (4 Vols., published between 1986 and 1991). Lisbon, Portugal: João Sá de Costa)]. The SLEUTH model calibration captured these city characteristics, and using the standard documented calibration procedures, seems to have adapted itself well to the European context. Useful predictions of growth to 2025, and investigation of the impact of planning and transportation construction can be investigated as a consequence of the successful calibration. Further application and testing of the SLEUTH model in non-Western environments may prove it to be the elusive universal model of urban growth, the antithesis of the special case urban models of the 1960s and 1970s.     

联邦开发过程中的校核、验证与确认（VV＆A）

对联邦的VV＆A不仅能够使每一步的工作得到跟踪和衡量,还使每一步能够减少多余的工作量,巩固需要加强的工作,明确开发人员的角色和职责,从而使人力、时间、资金等资源得到更加有效率的利用,仿真的结果变得更加可预测和准确,在很大程度上减少了编程的风险.联邦成员描述了仿真模型的各对象类、交互类、相关的属性、参数等信息,而联邦是各联邦成员的有机集成,构成具有特定功能的仿真系统.因此,联邦成员的正确性是联邦正确性的前提,决定了仿真系统的成败.在VV＆A的过程中,最好采用一些自动化工具以便于工作,同时要根据具体仿真系统的实际情况来确定VV＆A所需要作的工作.     

随机需求下双渠道供应链库存动态交互优化

针对双渠道供应链库存系统导致的缺货与库存积压等问题,在线上线下均为随机需求的条件下,考虑生产延迟和物流延迟,建立了双渠道库存的单独控制、集中控制和交叉补货控制这三种模式的动态优化模型。首先,以库存动态微分方程为基础,创新性地以控制理论为指导思想,以泰勒展开和拉普拉斯变换为手段,得到双渠道库存系统的反馈传递函数;其次,考虑了交叉补货的进销存过程中的周期间交互、上下游间交互以及渠道间交互,利用延迟控制、反馈控制和比例-积分-微分（PID）控制构造了双输入、双输出的复杂交互系统,以此寻求双渠道库存系统自身以及渠道间的动态供需双平衡,优化双渠道库存持有量,降低缺货次数和缺货量并使其保持动态稳定状态;最后,通过数值仿真实验,对比三种双渠道库存控制策略。仿真结果表明,在线上线下渠道为不同分布的随机需求时,交叉补货控制的剩余库存比独立库存控制降低了4.9%,交叉补货控制的缺货率与独立控制和集中控制相比分别下降了66.7%和60%。实验结果表明,在线上线下渠道为不同分布的随机需求的情况下使用双渠道交叉补货策略能很好地降低库存持有量,减少缺货次数和缺货量,从而节约库存成本。     

一种基于对象信息的MIS自适应生成器

为解决MIS在开发和运行过程中因需求频繁变更所带来的开发和维护的工作量上升问题,提出一种新的MIS软件基础模块自适应生成管理器。通过信息化管理MIS的版本、用户与权限、系统结构、系统模块、对象信息、通用视图元素、通用业务逻辑元素和通用数据访问方式,并基于通用的界面层基础元素、业务逻辑层基础元素、数据访问层基础元素和对象信息自适应生成或重构MIS软件基础模块的数据库、交互界面、业务逻辑、数据交互部分和软件内部结构,以达到动态构建和管理MIS软件基础模块,实现基础模块信息化和系统对自身信息化、自动化管理的目的。通过将该生成器技术实现并实际应用于MIS开发,验证其能够较好地应对MIS基础模块的快捷构建与变更,有效降低MIS开发与维护的工作量。该生成器较好地解决了MIS软件基础模块快速构建与重构问题,能较好地应对MIS在开发和运行过程中的频繁变更。     

On Belief and the Making of All Things Beautiful and Sublime: Creation by Ordinance and Destruction by Chaos

This is a study of beauty as a construct and a property of structural composition. I examine alternate possibilities of structural compositions, linguistics, or material arguments that beauty, impossible in utter chaos, might not be definitely found in order, but the latter is essential thereto. A distinction is also made between complex systems of order found in nature, often qualified as organic—the seemingly free and flowing forms found in formal sophistication beyond simple geometrical reduction—and the absence of order as pure chaos. Beauty is examined through order from historical linguistic, perceptual, and systemic constructivist perspectives, along with the sublime and the harmonious. Linguistically, order is a term of convergence of the seemingly disparate streams of significance of rank—in society, religion, and the belief in collective constants—and ornament is a term of bearing beauty and enhancement of taste that emanates from within the structure and should not be reduced to superficial application. I cite costume, including accessories of weaponry, as moments of proximity between style, purpose, utility, and the collective as semiotic bearer of meaning in culture and social order.     

Ethical and legal issues for writing researchers in an age of media convergence

With the convergence of digital media into ever-widening social and technological networks for creation and distribution, the contexts for writing and the study of writing and writers have certainly changed. Researchers must navigate a dense matrix of ethical and legal issues in all phases of research when studying the ever-changing processes and products of digital communications. In this article, I draw from numerous sources to articulate a few of the challenges facing digital writing researchers in this age of convergence, focusing on issues of representation (researcher, participant, third-party), issues of informed consent, and issues of copyright and fair use.     

基于WinSocket远程控制程序的设计与实现

详细介绍了Socket通信的初始化、建立,以及信息的传输、读取和执行控制指令的过程。该程序直接应用Windows系统的API函数,通过获取桌面图象,转换为位图格式进行发送和接收,以及图象处理和显示,还包括鼠标事件的获取、传输及实现相应鼠标操作事件等,实现屏幕控制技术。     

元宇宙发展演变及安全风险研究

近期元宇宙热潮席卷全球,主要国家和知名企业纷纷布局以争夺未来数字领域话语权,但目前关于元宇宙并没有形成较为统一的标准定义和终极形态描述。我国在促进电子信息产业高质量发展、保障网络空间安全的需求下,亟需科学认识元宇宙的本质特征、演变趋势及安全风险。运用文献调研和情报分析相结合的研究方法,首先基于技术应用迭代、经济商业模式、社会关系作用等核心理念归纳提出了元宇宙的基本概念,根据空间范畴、时空维度、关键技术、虚实交互等演进程度,将元宇宙发展演变依次划分为数据创生、数字仿生、虚拟镜生、虚实共生4个阶段并阐述了各阶段特征及对应形态;接着从创新应用需求、虚拟生活转变、商业价值驱动、政治力量推动等角度,分析了元宇宙广受关注的主要原因;然后针对挑战国家治理体系、冲击主流意识形态、操纵收割资本市场、引发诸多社会问题、误导技术产业布局等方面,重点研判了元宇宙浪潮带来的政治、文化、经济、社会和技术等多重安全风险和威胁。研究建议,目前元宇宙尚处于概念完善和产品探索阶段,应理性把握元宇宙发展机遇,立足我国电子信息产业现状,提前做好风险应对准备,构建数字治理监管体系,激发产业创新开放发展,夯实网络信息安全支撑,营...     

基于RFID的供港蔬菜安全监管溯源系统

为保障供港蔬菜的安全,提高供港蔬菜的安全监管能力,本文从检验检疫部门监管工作实际出发,提出了基于射频识别技术的供港蔬菜安全监管溯源系统．首先介绍了RFID技术及其主要功能,通过检验检疫角度提出供港蔬菜的业务框架结构、技术框架结构和安全保障体系结构,在此基础上设计溯源系统种植基地、加工厂、口岸和超市四个点的功能需求,并规定了溯源系统与RFID的接口标准．实践证明,该系统能够实现供港蔬菜流转中的每一管理节点的上下游追溯,实现管理者对蔬菜从原料、生产、运输到销售全过程的了解和把握,使企业的生产、仓储、通关、配送过程更加便捷,全面保证了蔬菜集装箱在运输过程的完好性,满足了供港蔬菜的安全溯源监管体系需求．该系统对食品的安全监管、产品的伪劣甄别有着重要的启示作用和意义．     

Fragile networks: identifying vulnerabilities and synergies in an uncertain age

This paper provides an overview of some of the recent developments in the assessment of network vulnerability and robustness through appropriate tools that assist in the quantification of network efficiency/performance and the identification of the importance of network components, such as nodes and links. We demonstrated how rigorously constructed and well‐defined network measures can capture not only the network topology underlying a particular critical system, but also the underlying behavior of decision‐makers, the resulting flows, and induced costs in the reality of demands for resources, whether fixed or elastic (price‐dependent). In addition, we reviewed how to determine the synergy associated with network integration, with a focus on supply chains, as may occur not only in corporate applications, such as in mergers and acquisitions, but also in humanitarian ones, as in the case of the creation of teams and partnerships for humanitarian logistics. We illustrated the concepts and tools in this paper, which are based on numerous publications, through a spectrum of applications and numerical examples. Because the number of disasters is growing globally, it is imperative to have transparent, well‐understood, and appropriate tools for the determination of network vulnerability and robustness, as critical infrastructure networks from transportation, telecommunications, supply chains, to financial and electric power ones, provide the ties that bind our economies and societies together. Local disruptions can have global impacts. Only when network components are identified as to their importance and rankings can decision‐makers and policy analysts, as well as planners and engineers, understand in an objective way which components should be maintained and protected the most, with implications for disaster and emergency preparedness as well as national security.     

Database management standards: status and applicability

This article presents the current status of existing and emerging ISO, ANSI, and FIPS standards for database management, specifically Database Languages NDL and SQL and Remote Database Access (RDA). It describes the general content of each standard and discusses its applicability, availability, completeness, maturity, stability, existing usage, and known limitations. Where appropriate, it also addresses the availability of conformance test suites and future plans for enhancements and follow-on standardization efforts.