Developing manufacturing control software: A survey and critique

The complexity and diversity of manufacturing software and the need to adapt this software to the frequent changes in the production requirements necessitate the use of a systematic approach to developing this software. The software life-cycle model (Royce, 1970) that consists of specifying the requirements of a software system, designing, implementing, testing, and evolving this software can be followed when developing large portions of manufacturing software. However, the presence of hardware devices in these systems and the high costs of acquiring and operating hardware devices further complicate the manufacturing software development process and require that the functionality of this software be extended to incorporate simulation and prototyping. This paper reviews recent methods for planning, scheduling, simulating, and monitoring the operation of manufacturing systems. A synopsis of the approaches to designing and implementing the real-time control software of these systems is presented. It is concluded that current methodologies support, in a very restricted sense, these planning, scheduling, and monitoring activities, and that enhanced performance can be achieved via an integrated approach.     

Prospect of manufacturing and design based on physiological polymorphism

Modern manufacturing and design should satisfy not only the requirements of high cost performance but also of the user. Besides that, the social environment which surrounds manufacturing is rapidly changing depending on new technologies. To create future products with user satisfaction, the effective use of human physiological data is essential. This is where knowledge of physiological anthropology can be applied. Physiological anthropologists have been pointing out a limit to the interpretation of the physiological data based on its average value. They have begun to notice that the physiological functions of humans show various types according to the blended effect of heredity and the surroundings. Adequate consideration of physiological polymorphism is indispensable to accomplish manufacturing that is well devised for human. In this study the concept of manufacturing and design based on physiological polymorphism is expressed. The target and the methodology for new manufacturing are discussed in seven fields, that is, welfare equipment, clothes, artificial tissue, sporting gear, furniture, building materials, and human interface. Through the above discussion, a procedure to achieve manufacturing and design based on physiological polymorphism is proposed.     

Managing water resources for crop production

Increasing crop production to meet the food requirements of the world''s growing population will put great pressure on global water resources. Given that the vast freshwater resources that are available in the world are far from fully exploited, globally there should be sufficient water for future agricultural requirements. However, there are large areas where low water supply and high human demand may lead to regional shortages of water for future food production. In these arid and semi-arid areas, where water is a major constraint on production, improving water resource management is crucial if Malthusian disasters are to be avoided. There is considerable scope for improvement, since in both dryland and irrigated agriculture only about one-third of the available water (as rainfall, surface, or groundwater) is used to grow useful plants. This paper illustrates a range of techniques that could lead to increased crop production by improving agricultural water use efficiency. This may be achieved by increasing the total amount of water available to plants or by increasing the efficiency with which that water is used to produce biomass. Although the crash from the Malthusian precipice may ultimately be inevitable if population growth is not addressed, the time taken to reach the edge of the precipice could be lengthened by more efficient use of existing water resources. <br>     

Modular synthesis of Petri nets for modeling flexible manufacturing systems

This paper proposes a modular Petri net synthesis method for modeling flexible manufacturing systems based on synchronization among control processes of the manufacturing resources (such as robots and machines). In the method, the target system is modeled in a bottom-up and uniform manner by first describing the system's control processes using strongly connected state machines (SCSMs) as the basic modules. Each SCSM may contain multiple tokens to represent resources from the same type such as spaces in a buffer. Next, the common transitions and common transition subnets of the modules are merged to represent their synchronization. The system model constructed is proven to be conservative and thus bounded. Moreover, a restricted class of merged nets is proven to be live and reversible. For general classes of merged nets, this paper shows theorems that easily calculateP-invariants of the final net without solving the linear system equations. TheseP-invariants can be used to help in verifying the model's qualitative properties such as liveness.     

A Genetic-Based Vision System for Cross-Functional Integration in Flexible Manufacturing: A Tutorial and Application

Machine vision has the potential to significantly impact both quality and productivity in automated manufacturing, due to its versatility, flexibility, and relative speed. Unfortunately, algorithmic development has not kept pace with advances in vision hardware technology, particularly in the areas of analysis and decision making. In this article, a tutorial is presented that explains how a genetic algorithm can be applied to vision systems for shape analysis and quality assessment. The control parameters for the algorithm are optimized by conducting experiments of Taguchi's approach to parameter design. The main objective behind this algorithm is to explain an application of the vision system that uses upstream design data of machined parts of different types for downstream metrology and quality decision making in the environment of flexible manufacturing. The part types used for demonstration are restricted to planar polygonal profiles generated by projecting 3D objects onto a 2D inspection plane. The input to the system is a set of boundary features of the part being analyzed, and the outputs from the system include the estimators of size, orientation, position, and out-of-profile error of the part. The system can analyze machined parts of different types without modifying software programs and parameter settings, which makes it generic and flexible, and is inherently suitable for on-line implementation in FMS environments.     

The Effects of Scheduling Rules and Routing Flexibility on the Performance of a Random Flexible Manufacturing System

The increased use of flexible manufacturing systems to efficiently provide customers with diversified products has created a significant set of operational challenges for managers. Many issues concerning procedures and policies for the day-to-day operation of these systems still are unresolved. Previous studies in this area have concentrated on various problems by isolating or simplifying the systems under study. The primary objective of this study is to extend previous research by examining the effects of scheduling rules and routing flexibility on the performance of a constrained, random flexible manufacturing system (FMS). Other experimental factors considered are shop load, shop configuration, and system breakdowns. Within the bounds of this experiment, the results indicate that, in the presence of total routing flexibility, the effects of shop load, system breakdowns, and scheduling rules are significantly dampened. In particular, when total routing flexibility exists, the choice of scheduling rules is not critical. We also show that the behavior of scheduling rules in a more constrained FMS environment (i.e., where system breakdowns occur and material handling capability is limited) is consistent with the findings of previous research conducted under less constrained environments. Finally, results indicate that the shop configuration factor has little or no impact on a system's flow-time performance.     

Functional landscapes in cities: a systems approach

Human enterprise and endeavour increasingly influence global processes of change, from the planetary scale down to the very local. Cities are hubs of human activity, and as the places where the majority of the world’s population live we must, when looking into an uncertain future, consider how we think about urban design. Cities are densely inhabited, lived-in landscapes where human presence and perceptions are deeply enmeshed with biophysical and built infrastructures. As such, they present complex mosaics of different habitats and competing uses, ever changing in response to human and physical drivers. If designed properly, green infrastructure can contribute many important functions to a city. Efforts to strategically make use of green infrastructure can benefit considerably from a systems perspective where linkages and cross-boundary dynamics are at the very least as important as individual components. Design, planning and governance of requirements for green infrastructure also extend far beyond biophysical elements and components. Recognition of interconnections between individual green spaces, green infrastructure and the built environment, the physical environment and diverse actors, and formal and informal governance arrangements—as outlined in the four design principles in this article—is a first important step towards a more comprehensive and inclusive approach, not least to green infrastructure planning and design.     

Regional material flow accounts for China: Examining China's natural resource use at the provincial and national level

Over the last three decades, China has experienced the most dynamic economic development lifting living standards and resulting in fast‐growing use of natural resources. In the past, the focus has been on national MFA accounts which do not do justice to the second largest economy, home to 19% of the world population and having 30% of global material use. In this research, we calculate material extraction for China at the regional level during 1995–2015 using the most recent available statistical data and applying the most up‐to‐date international calculation methods. In particular, we combine a bottom‐up and top‐down approach for constructing the dataset of China's economically used Domestic Extraction (DEU) in an integrated way. This approach also improves the Chinese national material flow accounts and allows us to present a reliable database of DE of materials for China to date. Our new dataset provides the basis for calculating material footprints and environmental impacts of China's regions. The dataset enables us to evaluate regional resource efficiency trends in China. We find that during the past two decades, China's material use has grown strongly from 11.7 billion tonnes in 1995 to 35.4 billion tonnes in 2015. Material use has accelerated between 2000 and 2010 but slowed down between 2010 and 2015 reflecting the economic contraction caused by the Global Financial Crisis which reduced the global demand for China's manufacturing and a reorientation of China's economic policy settings toward quality of growth. Unsurprisingly, different regions play different roles in the supply chain of materials, achieving different economic performances resulting in very diverse material efficiency outcomes. This information is important to allow for a targeted policy approach to increase resource efficiency, reduce environmental impacts of resource use, and grow wellbeing in China with large positive implications for global sustainability. This study provides the basis for the development of relevant resource management policies for different regions in the future.     

Evaluating the cascading-use of wood furniture: How value-retention processes can contribute to material efficiency and circularity

As utilized technical products, durable wood furniture plays an important role in a future circular economy (CE). However, contemporary CE literature predominantly focuses on wood's biochemical properties and its potential as a consumable material within the bio-cycle. This perspective prevents meaningful consideration of CE strategies for the wood products sector, particularly for value-retention processes (VRPs), including reuse, repair, and refurbishment. We adapt and apply the VRP model introduced by the UN International Resource Panel (IRP) to wood furniture products to quantify select environmental benefits made possible through cascading-use, via VRPs (vs. new manufacturing). Unlike traditional life cycle assessment (LCA), this model accounts for impacts incurred and avoided through product life-extension and VRPs, relative to conventional systems of new manufacturing, disposal, and replacement. Three case studies of wood-based chairs are conducted to demonstrate this new application of the VRP model to compare the relative environmental impacts associated with wood furniture that is diverted to cascading-use, prior to recycling. In collaboration with industry partners, new material requirements (kg/unit), energy requirements (kWh/unit), emissions (kg CO2-e./unit), and waste generation (kg/unit) were calculated for newly manufactured chairs (OEM new) and subsequent cascading-use via reuse, repair, and refurbishment. The differing degrees of environmental impact avoidance and material efficiency are presented for each case study product and VRP, to provoke discussion and future research regarding the effective and optimal utilization of technical, durable wooden furniture within a CE.     

Nesting,brood rearing,and summer habitat selection by translocated greater sage‐grouse in North Dakota,USA

Human enterprise has led to large‐scale changes in landscapes and altered wildlife population distribution and abundance, necessitating efficient and effective conservation strategies for impacted species. Greater sage‐grouse (Centrocercus urophasianus; hereafter sage‐grouse) are a widespread sagebrush (Artemisia spp.) obligate species that has experienced population declines since the mid‐1900s resulting from habitat loss and expansion of anthropogenic features into sagebrush ecosystems. Habitat loss is especially evident in North Dakota, USA, on the northeastern fringe of sage‐grouse’ distribution, where a remnant population remains despite recent development of energy‐related infrastructure. Resource managers in this region have determined a need to augment sage‐grouse populations using translocation techniques that can be important management tools for countering species decline from range contraction. Although translocations are a common tool for wildlife management, very little research has evaluated habitat following translocation, to track individual behaviors such as habitat selection and fidelity to the release site, which can help inform habitat requirements to guide selection of future release sites. We provide an example where locations from previously released radio‐marked sage‐grouse are used in a resource selection function framework to evaluate habitat selection following translocation and identify areas of seasonal habitat to inform habitat management and potential restoration needs. We also evaluated possible changes in seasonal habitat since the late 1980s using spatial data provided by the Rangeland Analysis Platform coupled with resource selection modeling results. Our results serve as critical baseline information for habitat used by translocated individuals across life stages in this study area, and will inform future evaluations of population performance and potential for long‐term recovery.     

Current development of biorefinery in China

To meet the demand of its fast growing economy, China has become already the second largest buyer of crude oil. China is facing critical problems of energy shortage and environment deterioration. Rational and efficient energy use and environment protection are both getting more attention in China. Biomass energy is renewable energy made from biological sources. China's biomass resources are abundant, which could provide energy for future social and economic development. However technologies for biomass resource conversion in China are still just beginning. In this paper, current biomass resource distribution and technologies of biomass energy, including power generation, biofuel production and biomass-based chemical production are reviewed.     

基于MSIASM和能源消费碳排放的中国四大直辖市社会代谢分析

通过社会代谢多尺度综合评估(Multi-Scale Integrated Assessment of Societal Metabolism,MSIASM)方法,采用生物-经济压力和不同组织尺度下的体外能代谢率、能源密度指标,并将能源消费碳排放融入评估框架,评价了中国四大直辖市2004年至2010年的社会代谢及其综合发展状况。研究中能源消费碳排放的加入较好补充了MSIASM在生态评估方面的弱势。研究结果显示,四大直辖市整体社会代谢发展良好,体外能代谢率和生物-经济压力稳步上升,能源密度和单位能耗碳排放不断降低,总体呈现良性发展态势。从各个直辖市的社会经济系统各部门表现来看,各城市体现了自己的突出特点。在深入到行业尺度研究体外能代谢率、能源密度后,整体显示出控制工业部门和交通运输部门的能耗增长对于提高经济生产能源效率的突出作用,同时应继续加大金融和计算机等低能耗高经济生产率行业的发展力度。     

A simple model for the influence of habitat resource availability on lateral clonal spread

Plant clonal spread is ubiquitous and of great interest, owing both to its key role in plant community assembly and its suitability for plant behaviour research. However, mechanisms that govern spreading distance are not well known. Here we link spacer costs and below-ground competition in a simple model of growth in a homogeneous below-ground environment, in which optimal distance between ramets is based on minimizing the sum of these costs. Using this model, we predict a high prevalence of clonal growth that does not employ spacers in resource-poor environments and a nonlinear increase in spreading distance in response to increasing below-ground resource availability. Analysis of database data on clonal growth in relationship to below-ground resource availability revealed that patterns of the spread based on stolons is compatible with the model''s predictions. As expected, model prediction failed for rhizomatous species, where spacer sizes are likely to be selected mainly to play roles other than spread. The model''s simplicity makes it useful as a null model in testing hypotheses about the effects of environmental heterogeneity on clonal spread.     

Disposable bioprocessing: The future has arrived

Increasing cost pressures are driving the rapid adoption of disposables in bioprocessing. While well ensconced in lab‐scale operations, the lower operating/ validation costs at larger scale and relative ease of use are leading to these systems entering all stages and operations of a typical biopharmaceutical manufacturing process. Here, we focus on progress made in the incorporation of disposable equipment with sensor technology in bioprocessing throughout the development cycle. We note that sensor patch technology is mostly being adapted to disposable cell culture devices, but future adaptation to downstream steps is conceivable. Lastly, regulatory requirements are also briefly assessed in the context of disposables and the Process Analytical Technologies (PAT) and Quality by Design (QbD) initiatives. Biotechnol. Bioeng. 2009;102: 348–356. © 2008 Wiley Periodicals, Inc.     

Process Monitoring Strategies for Surface Mount Manufacturing Processes

Establishing reliable surface mount assemblies requires robust design and assembly practices, including stringent process control schemes for achieving high yield processes and high quality solder interconnects. Conventional Shewhart-based process control charts prevalent in today's complex surface mount manufacturing processes are found to be inadequate as a result of autocorrelation, high false alarm probability, and inability to detect process deterioration. Hence, new strategies are needed to circumvent the shortcomings of traditional process control techniques. In this article, the adequacy of Shewhart models in a surface mount manufacturing environment is examined and some alternative solutions and strategies for process monitoring are discussed. For modeling solder paste deposition process data, a time series analysis based on neural network models is highly desirable for both controllability and predictability. In particular, neural networks can be trained to model the autocorrelated time series, learn historical process behavior, and forecast future process performance with low prediction errors. This forecasting ability is especially useful for early detection of solder paste deterioration, so that timely remedial actions can be taken, minimizing the impact on subsequent yields of downstream processes. As for the automated component placement process where very low fraction nonconforming frequently occurs, control-charting schemes based on cumulative counts of conforming items produced prior to detection of nonconforming items is more sensitive in flagging process deterioration. For the reflow soldering and wave-soldering processes, the use of demerit control charts is appealing as it provides not only better control when various defects with a different degree of severity are encountered, but also leads to an improved ARL performance. Illustrative examples of actual process data are presented to demonstrate these approaches.     

基于生态系统服务理论的中国绿色经济转型预测分析

着眼于中国绿色经济转型之路的科学预测与分析,借鉴传统环境负荷模型以及资源与经济脱钩理论、区位熵理论等,提出基于生态系统服务理论的有关绿色经济指标评价模型。应用该模型计算出2001—2010年全球及中国有关绿色经济指标,依照未来中国经济与社会发展规划目标,预计"十二五"末期中国经济发展中的资源消耗及环境损失成本、人均绿色GDP将分别达到3.11×1012美元、0.37×104美元,生态负荷强度、资源脱钩指数及绿色GDP的区位熵指数分别为0.38、0.66、75;2020年中国绿色GDP的区位熵指数将超越全球平均水平、2024年人均GDP将突破1万美元关口步入中等发达国家行列。计算结果表明中国生态系统压力逐年降低、资源利用效率、环境绩效与经济效益同步提高,逐渐在全球经济绿色转型过程中发挥重要作用;未来,中国仍需秉承"共同但有区别的责任"原则,处理好与其他国家的权责纷争;同时积极推进节能减排、经济结构调整工作,进一步协调好城乡之间、区域之间经济社会发展与自然资源及生态环境的关系。     

Back to the Roots: The Integration of a Constructed Wetland into a Recirculating Hatchery - A Case Study

Aquaculture is currently one of the fastest growing food-producing sectors, accounting for around 50% of the world''s food fish. Limited resources, together with climatic change, have stimulated the search for solutions to support and sustain the production of fish as a nutritious food. The integration of a constructed wetland (CW) into a recirculating hatchery (RHS) was evaluated with respect to its economic feasibility and environmental impact. The outcome of eight production cycles showed the potential of CW integration for expanded production without increased operation costs or environmental load. Concretely, the use of constructed wetland allows the rearing about 40% more fish biomass, resulting in higher production and profitability. The low requirements for space, fresh water, and energy enable the establishment of such systems almost anywhere. Constructed wetlands could enhance the productivity of existing small scale facilities, as well as larger systems, to address economic and environmental issues in aquaculture. Such systems have potential to be sustainable in the context of possible future climate change and resource limitations.     

Reciprocal Regulation as a Source of Ultrasensitivity in Two-Component Systems with a Bifunctional Sensor Kinase

Two-component signal transduction systems, where the phosphorylation state of a regulator protein is modulated by a sensor kinase, are common in bacteria and other microbes. In many of these systems, the sensor kinase is bifunctional catalyzing both, the phosphorylation and the dephosphorylation of the regulator protein in response to input signals. Previous studies have shown that systems with a bifunctional enzyme can adjust the phosphorylation level of the regulator protein independently of the total protein concentrations – a property known as concentration robustness. Here, I argue that two-component systems with a bifunctional enzyme may also exhibit ultrasensitivity if the input signal reciprocally affects multiple activities of the sensor kinase. To this end, I consider the case where an allosteric effector inhibits autophosphorylation and, concomitantly, activates the enzyme''s phosphatase activity, as observed experimentally in the PhoQ/PhoP and NRII/NRI systems. A theoretical analysis reveals two operating regimes under steady state conditions depending on the effector affinity: If the affinity is low the system produces a graded response with respect to input signals and exhibits stimulus-dependent concentration robustness – consistent with previous experiments. In contrast, a high-affinity effector may generate ultrasensitivity by a similar mechanism as phosphorylation-dephosphorylation cycles with distinct converter enzymes. The occurrence of ultrasensitivity requires saturation of the sensor kinase''s phosphatase activity, but is restricted to low effector concentrations, which suggests that this mode of operation might be employed for the detection and amplification of low abundant input signals. Interestingly, the same mechanism also applies to covalent modification cycles with a bifunctional converter enzyme, which suggests that reciprocal regulation, as a mechanism to generate ultrasensitivity, is not restricted to two-component systems, but may apply more generally to bifunctional enzyme systems.     

Resource partitioning and interspecific competition in snakes: the search for general geographical and guild patterns

The role of interspecific competition as a key factor in the ecology of natural communities where species exploit limited resources is well established, and the study of competition dynamics in snake communities has received much attention in recent years. Twenty years ago, an acclaimed review ( Toft 1985 ) suggested that snakes were atypical among vertebrates because sympatric species usually partition the food niche. Here, I review the articles published in the last two decades with the aim of finding any general geographical or guild patterns and assessing if Toft's main conclusion is still supported by new evidence. Where appropriate, I use Monte Carlo simulations to establish whether observed patterns of niche overlap are real, or if they have occurred by chance. My study shows clear congruence in the patterns of coexistence exhibited by snake communities in different regions of the world, i.e.: (1) cold regions of the northern hemisphere (high latitudes and altitudes) exhibit low species richness and a very low, or even absent, potential for interspecific competition; (2) aquatic snakes that form communities in temperate regions generally partition the food type available and exhibit a broad similarity in habitat use with subtle differences in microhabitat use; (3) terrestrial snake communities in temperate regions are very variable in terms of their coexistence dynamics and show no evidence of generalised patterns; (4) sympatric viperids in Europe, North America and, most interestingly, tropical Asia partition the available habitat but not the prey resource; (5) competition is much stronger in tropical snake communities, and the intensity of this process fluctuates throughout the year being most intense during periods of low food availability; (6) in general, tropical snakes partition the food resource (prey type and/or prey size), but when this resource is not partitioned competitive exclusion can occur. Prey resource availability is a fundamental variable for all snake communities; this is clearly documented by studies on terrestrial snakes in Australia where, due to a relative scarcity of prey availability in the field, sympatry among species is much rarer than in other continents. I conclude that, although there are several notable exceptions, Toft's main conclusion is still supported by empirical evidence. However, I disagree with Toft's conclusion that most snakes are food specialists, and I contend that interspecific competition is important in structuring many (if not most) of the snake communities around the world.