Particle swarm optimization: an alternative in marine propeller optimization?

This article deals with improving and evaluating the performance of two evolutionary algorithm approaches for automated engineering design optimization. Here a marine propeller design with constraints on cavitation nuisance is the intended application. For this purpose, the particle swarm optimization (PSO) algorithm is adapted for multi-objective optimization and constraint handling for use in propeller design. Three PSO algorithms are developed and tested for the optimization of four commercial propeller designs for different ship types. The results are evaluated by interrogating the generation medians and the Pareto front development. The same propellers are also optimized utilizing the well established NSGA-II genetic algorithm to provide benchmark results. The authors' PSO algorithms deliver comparable results to NSGA-II, but converge earlier and enhance the solution in terms of constraints violation.     

Decarbonising road freight: Is truck automation and platooning an opportunity?

Clean Technologies and Environmental Policy - Governments, industry and academia are paying high attention to autonomous vehicles and platooning, due to their high potential to transform public and...     

Academic social networks metrics: an effective indicator for university performance?

Scientometrics - Social networks have become popular among researchers and scientists. Specialized platforms for researchers offer many metrics and indicators which are used to evaluate various...     

Oral intake during hemodialysis: Is there an association with intradialytic hypotension?

Oral intake (OI) of food and fluid has been associated with hypotension during hemodialysis (HD). Trials evaluating this relationship are small. The objective of this study was to quantify OI and to examine its association with hypotension during HD. This is a cross-sectional retrospective chart review study of 3 consecutive HD runs (dialysate iCa=1.25 mmol/L) in 126 stable HD patients (n=378). For each run, the calculation for OI=total ultrafiltration-(net weight loss+IV fluids given). Hypotension was defined as a systolic blood pressure of <100 mmHg at any point during the run. The mean age of the patients was 60.9 years, 38.2% were female, 30.2% had diabetes mellitus, and the majority were Caucasian. The mean (SD) OI was 0.27 (0.352) L/run, range -1.061 to 1.901 L/run, with a normal distribution. In bivariate analysis, there was no correlation of OI with systolic blood pressure, diastolic blood pressure, or mean blood pressure (BP), and the mean OI did not differ among runs with hypotension (n=78) compared with uncomplicated runs (p=0.93). Oral intake was not predictive of hypotension in a multiple logistic regression model controlling for vintage, age, sex, BP medications, coronary disease, dialysis day and shift, diabetes mellitus, s-Ca, Na and ultrafiltration profiles, and dialysis temperature, even when the analysis was restricted to runs where the patients reached the prescribed dry weight within 0.1 kg. The results of this study suggest that the mean OI during dialysis is just over 0.25 kg, with some patients consuming several kilograms. The clinical significance of OI is uncertain. We did not find an association between OI and hypotension. It is likely that this association was confounded by failure to achieve the prescribed dry weight in a proportion of patients with a high OI, as well as interventions implemented in response to hypotension in previous runs. For example, patients with previous episodes of low BP are advised to limit OI, are prescribed profiles, and so on. There may be other deleterious effects of high OI including hypertension and cardiac disease. The generalizability of the results of this largely Caucasian study population is a recognized limitation. Further prospective and blinded studies are needed to examine the association between OI and hypotension, the long-term clinical consequences of OI, and to define thresholds for recommended OI during dialysis.     

Allocating reforestation areas for sediment flow minimization: an?integer programming formulation and?a?heuristic solution method

Policy and decision makers dealing with environmental conservation and land use planning often require identifying potential sites for contributing to minimize sediment flow reaching riverbeds. This is the case of reforestation initiatives, which can have sediment flow minimization among their objectives. This paper proposes an Integer Programming (IP) formulation and a Heuristic solution method for selecting a predefined number of locations to be reforested in order to minimize sediment load at a given outlet in a watershed. Although the core structure of both methods can be applied for different sorts of flow, the formulations are targeted to minimization of sediment delivery. The proposed approaches make use of a Single Flow Direction (SFD) raster map covering the watershed in order to construct a tree structure so that the outlet cell corresponds to the root node in the tree. The results obtained with both approaches are in agreement with expert assessments of erosion levels, slopes and distances to the riverbeds, which in turn allows concluding that this approach is suitable for minimizing sediment flow. Since the results obtained with the IP formulation are the same as the ones obtained with the Heuristic approach, an optimality proof is included in the present work. Taking into consideration that the heuristic requires much less computation time, this solution method is more suitable to be applied in large sized problems.     

Is subsidizing entry an optimal policy?

Public subsidies in support of new firm foundation are amongthe most frequently used instruments of industrial policy inthe Euro zone. This paper analyses their effectiveness and efficiencyvis-à-vis some features of the overall process of industrydynamics in Italian manufacturing. To this end, the survivaland growth patterns of new small firms are investigated usinga unique dataset on electrical and electronic engineering inItaly. As regards survival, our results confirm the findingsof other studies, namely that the hazard rates are particularlyhigh in the early stages of firm's lifecycle. As far as growthis concerned, the main finding in this study is that Gibrat'sLaw fails to hold in the years immediately following start-up,when smaller firms must ‘rush’ in order to achievea size large enough to enhance their likelihood of survival;conversely, in later stages of a firm's lifecycle this Law cannotbe ignored. These results radically question the use of subsidiesas an optimal policy for the support of new entries, since thesubsidy brings about a major bias in the process of market selection(including substitution and deadweight effects) and hampersthe post-entry scale adjustment of newborn firms.     

Nanotechnologie: Eine neue soziale Dynamik an der Schnittstelle zwischen Wissenschaft und ?ffentlichkeit

This paper investigates the development of nanotechnology from three different points of view: (1) as a new technology, (2) as social dynamics, and (3) as an ideology. It argues that nanotechnology is not a new technology but a new social dynamics guided by programmatic ideas and situated at the interface between science and the public. Rather than being determined by social constructivism, the main argument is based on the poor scientific and technological identity of nanotechnology. Finally the paper concludes that nanotechnology is to be considered an extension and increase of materials science and engineering, not only scientifically but in particular socially and ideologically, by pointing out common characteristics and differences.     

1970s: Turn of an Era in the History of Science?1

The decade of the 1970s has recently received a lot of attention in historical research. It is commonly described as ‘a turn of an era’, a time of deep economic, social and cultural transformation. Where do the sciences feature in this picture of the 1970s? This spotlight sheds light on an understudied period of time in the history of science.     

How flat is an air-cleaved mica surface?

Muscovite mica is an important mineral that has become a standard substrate, due to its easy cleavage along the {001} planes, revealing a very flat surface that is compatible with many biological materials. Here we study mica surfaces by dynamic atomic force microscopy (AFM) operated in the non-contact mode (NC-AFM) under ultra-high vacuum (UHV) conditions. Surfaces produced by cleaving in UHV cannot be imaged with NC-AFM due to large surface charges; however, cleavage in air yields much less surface charge and allows for NC-AFM imaging. We present highly resolved NC-AFM images of air-cleaved mica surfaces revealing a rough morphology originating from a high density of nanometre-sized particles. Among these particles, we find regularly shaped structures indicating the growth of crystallites on the surface. The contamination layer cannot be removed by degassing in UHV; even prolonged heating at a temperature of 560?K under UHV conditions does not yield an atomically flat surface.     

The Lithium/Air Battery: Still an Emerging System or a Practical Reality?

Lithium/air is a fascinating energy storage system. The effective exploitation of air as a battery electrode has been the long‐time dream of the battery community. Air is, in principle, a no‐cost material characterized by a very high specific capacity value. In the particular case of the lithium/air system, energy levels approaching that of gasoline have been postulated. It is then not surprising that, in the course of the last decade, great attention has been devoted to this battery by various top academic and industrial laboratories worldwide. This intense investigation, however, has soon highlighted a series of issues that prevent a rapid development of the Li/air electrochemical system. Although several breakthroughs have been achieved recently, the question on whether this battery will have an effective economic and societal impact remains. In this review, a critical evaluation of the progress achieved so far is made, together with an attempt to propose future R&D trends. A forecast on whether Li/air may have a role in the next years' battery technology is also postulated.     

An Efficient SQUID NDE Defect Detection Approach by?Using?an?Adaptive?Finite-Element?Modeling

Incorporating the finite-element method for the modeling of the SQUID NDE response to a predefined defect pattern, an adaptive algorithm has been developed for the reconstruction of unknown defects using an optimization algorithm for updating of the forward problem. The defect reconstruction algorithm starts with an initial estimation for the defect pattern. Then the forward problem is solved and the obtained field pattern is compared with the measured signal from the SQUID NDE system. The result is used by an optimization algorithm to update the defect structure to be incorporated in the FEM forward problem for the next iteration. Since the mentioned model based inverse algorithm normally consumes a lot of computational resources, the number of iterations plays an important role in the determination of the total response convergence time. Consequently, different optimization algorithms have been applied and their performances are compared. In this work by incorporating an efficient forward model and using the stochastic and deterministic optimization algorithms for defect updating we have investigated their performance on the inversion of the SQUID NDE signal and also their ability to defect reconstruction in the noisy environment.     

Benchmarking international scientific excellence: Are highly cited research papers an appropriate frame of reference?

This paper introduces a citation-based "systems approach" for analyzing the various institutional and cognitive dimensions of scientific excellence within national research systems. The methodology, covering several aggregate levels, focuses on the most highly cited research papers in the international journal literature. The distribution of these papers across institutions and disciplines enables objective comparisons their (possible) international-level scientific excellence. By way of example, we present key results from a recent series of analyses of the research system in the Netherlands in the mid 1990s, focussing on the performance of the universities across the various major scientific disciplines within the context of the entire system"s scientific performance. Special attention is paid to the contribution in the world"s top 1% and top 10% most highly cited research papers. The findings indicate that these high performance papers provide a useful analytical framework - both in terms of transparency, cognitive and institutional differentiation, as well as its scope for domestic and international comparisons - providing new indicators for identifying "world class" scientific excellence at the aggregate level. The average citation scores of these academic "Centres of Scientific Excellence" appear to be an inadequate predictor of their production of highly cited papers. However, further critical reflection and in-depth validation studies are needed to establish the true potential of this approach for science policy analyses and evaluation of research performance. This revised version was published online in August 2006 with corrections to the Cover Date.     

Developing markets for forest environmental services: an opportunity for promoting equity while securing efficiency?

Market-based approaches to environmental management are all the rage. Claims that market mechanisms can encourage environmental protection and promote greater economic efficiency while saving taxpayers' money are tantalizing. In the forestry sector, policy makers are widely heeding this advice and shrinking command-and-control systems in favour of incentive mechanisms that seek to align private enthusiasm with the public good. In some cases, governments are even promoting the creation of markets where none existed before. In others, markets are evolving of their own accord. In such times of change, it is difficult to stand back and take stock. Yet, it is during such times that guidance is most needed. In the rush to introduce market-based solutions to environmental problems, a particular concern is how markets are impacting on the poor. In this paper an effort is made to draw on a recent review of markets for four forest environmental services (biodiversity conservation, carbon sequestration, watershed protection and landscape beauty) to draw out preliminary insights into how markets are performing with respect to their impacts on the poor. The evidence suggests a need for caution. While the potential benefits are significant, the poor face an uphill battle in realizing them. Key constraints facing the poor include a lack of property rights over forest resources and their environmental services; inadequate skills and education; poor market information; lack of market contacts; inadequate communication infrastructure; inappropriate contract design; and lack of access to financial resources. To tackle these, four potential ways forward are highlighted: (1) assign property rights to forest assets and their related environmental services in ways that respect customary arrangements and poor people's tenure; (2) strengthen capacity for market participation, e.g. through training and education; (3) invest in the provision of market information, advice and, essentially, a contact point for buyers and sellers, perhaps through the establishment of a 'market support centre'; and (4) improve access to finance so that poor individuals can make necessary up-front investments in market participation.