Low Level Of Complexity Research Articles

An augmented system approach for LMI-based control design of constrained Takagi-Sugeno fuzzy systems

In this paper, we address the control design of a class of constrained Takagi-Sugeno fuzzy systems. These systems are subject to both control input and state constraints. Sufficient design conditions are derived via a judicious use of an equivalent augmentation form of the closed-loop system together with a new parameter-dependent Lyapunov function. The control input nonlinearity is dealt with via a generalized sector condition. These instrumental control tools allow reducing significantly the conservatism of the results while keeping a simple control structure with a low level of numerical complexity. In particular, it has been shown that in many cases the new method can provide better results (in terms of conservatism reduction) than some recent works developed in non-quadratic Lyapunov framework. Several numerical examples are given to illustrate the effectiveness of the proposed method.

An EEMD-based multi-scale fuzzy entropy approach for complexity analysis in clean energy markets

To measure the efficiency of clean energy markets, a multi-scale complexity analysis approach is proposed. Due to the coexisting characteristics of clean energy markets, the “divide and conquer” strategy is introduced to provide a more comprehensive complexity analysis framework for both overall dynamics and hidden features (in different time scales), and to identify the leading factors contributing to the complexity. In the proposed approach, ensemble empirical mode decomposition (EEMD), a competitive multi-scale analysis tool, is first implemented to capture meaningful features hidden in the original market system. Second, fuzzy entropy, an effective complexity measurement, is employed to analyze both the whole system and inner features. In empirical analysis, the nuclear energy and hydropower markets in China and US are investigated, and some interesting results are obtained. For overall dynamics, the US clean energy markets appear a significantly higher complexity level than China’s markets, implying market maturity and efficiency of US clean energy relative to China. For inner features, similar features (in terms of similar time scales) in different markets present similar complexity levels. For different inner features, there are some distinct differences in clean energy markets between US and China. China’s markets are mainly driven by upward long-term trends with a low-level complexity, while short-term fluctuations with high-level complexity are the leading features for the US markets. All these results demonstrate that the proposed EEMD-based multi-scale fuzzy entropy approach can provide a new analysis tool to understand the complexity of clean energy markets.

Sources of difficulty in assessment: example of PISA science items

ABSTRACTThe understanding of what makes a question difficult is a crucial concern in assessment. To study the difficulty of test questions, we focus on the case of PISA, which assesses to what degree 15-year-old students have acquired knowledge and skills essential for full participation in society. Our research question is to identify PISA science item characteristics that could influence the item’s proficiency level. It is based on an a-priori item analysis and a statistical analysis. Results show that only the cognitive complexity and the format out of the different characteristics of PISA science items determined in our a-priori analysis have an explanatory power on an item’s proficiency levels. The proficiency level cannot be explained by the dependence/independence of the information provided in the unit and/or item introduction and the competence. We conclude that in PISA, it appears possible to anticipate a high proficiency level, that is, students’ low scores for items displaying a high cognitive complexity. In the case of a middle or low cognitive complexity level item, the cognitive complexity level is not sufficient to predict item difficulty. Other characteristics play a crucial role in item difficulty. We discuss anticipating the difficulties in assessment in a broader perspective.

Physics-Based Analytical Model for Input, Output, and Reverse Capacitance of a GaN HEMT With the Field-Plate Structure

This paper presents an analytical model for input, output, and reverse capacitance of a normally on AlGaN/GaN high-electron mobility transistor (HEMT) with a gate field-plate structure, when the device is in the subthreshold regime. Together with the existing model for the output I–V characteristics, the proposed capacitance model provides the complete set of analytical equations that relate the physical design parameters to the electrical characteristics of the device. The model was verified by the experimental characterization of a HEMT. In comparison to the physics-based models implemented in Finite Element Analysis tools, the obtained capacitance model has substantially lower level of complexity and, therefore, it is more suitable for implementation into iterative design optimization algorithms. In order to verify the proposed model for such usage, the prototype of a high-frequency buck converter was built, using previously modeled GaN HEMT as the main switch. The hybrid analytical-behavioral power loss model of a high-frequency buck converter was implemented into Simplorer simulation tool, using the proposed physics-based model as the device description for the capacitive part. The efficiency measurements showed good agreement with the simulation results, even at 20 MHz of switching frequency in the low range of the output power.

Don't Lose Your Brain at Work - The Role of Recurrent Novelty at Work in Cognitive and Brain Aging.

Cognitive and brain aging is strongly influenced by everyday settings such as work demands. Long-term exposure to low job complexity, for instance, has detrimental effects on cognitive functioning and regional gray matter (GM) volume. Brain and cognition, however, are also characterized by plasticity. We postulate that the experience of novelty (at work) is one important trigger of plasticity. We investigated the cumulative effect of recurrent exposure to work-task changes (WTC) at low levels of job complexity on GM volume and cognitive functioning of middle-aged production workers across a time window of 17 years. In a case-control study, we found that amount of WTC was associated with better processing speed and working memory as well as with more GM volume in brain regions that have been associated with learning and that show pronounced age-related decline. Recurrent novelty at work may serve as an ‘in vivo’ intervention that helps counteracting debilitating long-term effects of low job complexity.

The Complex Cardiac Atherosclerotic Disorder: The Elusive Role of Genetics and the New Consensus of Systems Biology Approach

<p>The present technological status of genetics and genomics or the genome-wide association studies (GWAS) are insufficient to explain complex diseases like atherosclerosis and coronary artery disease (CAD). It appears that the genetic risk variants of atherosclerosis are activated concurrently with functionally active specific environmental risk factors. With the systems biology methodological approach the atherosclerotic process and CAD are better explained and studied as a unified entity with significant clinical consequences.</p><p>Systems biology is an alternative approach for the study of atherosclerosis and CAD. With the systems biology approach the follow-up of the atherosclerotic process requires four conceptual areas of study: 1) the two potential directions, the bottom-up direction (functional composition from genes to phenotypes) and the top-down direction (functional decomposition from phenotypes to genes); 2) the four disciplines or levels of complexity: the genomic, the cellular, the modular and the model (clinical phenotype) level; 3) the concept of network construction; 4) the atherosclerotic plaque development and progression across all levels of complexity.</p><p>The systems biology methodology is holistic in conception. The proposed systems patterns are able to follow up the progressive nature of atherosclerosis and to explain the appearance of the clinical cardiovascular phenotypes. The phenotypes of CAD are integrated clinical wholes that determine through constrains and therapeutic procedures the behavior of the biological parts in the lower levels of complexity. This way of thinking is leading from genomics, through networks, to the mainstay of clinical cardiology. </p>

High resolution modelling of soil moisture patterns with TerrSysMP: A comparison with sensor network data

The prediction of the spatial and temporal variability of land surface states and fluxes with land surface models at high spatial resolution is still a challenge. This study compares simulation results using TerrSysMP including a 3D variably saturated groundwater flow model (ParFlow) coupled to the Community Land Model (CLM) of a 38ha managed grassland head-water catchment in the Eifel (Germany), with soil water content (SWC) measurements from a wireless sensor network, actual evapotranspiration recorded by lysimeters and eddy covariance stations and discharge observations. TerrSysMP was discretized with a 10×10m lateral resolution, variable vertical resolution (0.025–0.575m), and the following parameterization strategies of the subsurface soil hydraulic parameters: (i) completely homogeneous, (ii) homogeneous parameters for different soil horizons, (iii) different parameters for each soil unit and soil horizon and (iv) heterogeneous stochastic realizations. Hydraulic conductivity and Mualem-Van Genuchten parameters in these simulations were sampled from probability density functions, constructed from either (i) soil texture measurements and Rosetta pedotransfer functions (ROS), or (ii) estimated soil hydraulic parameters by 1D inverse modelling using shuffle complex evolution (SCE).The results indicate that the spatial variability of SWC at the scale of a small headwater catchment is dominated by topography and spatially heterogeneous soil hydraulic parameters. The spatial variability of the soil water content thereby increases as a function of heterogeneity of soil hydraulic parameters. For lower levels of complexity, spatial variability of the SWC was underrepresented in particular for the ROS-simulations. Whereas all model simulations were able to reproduce the seasonal evapotranspiration variability, the poor discharge simulations with high model bias are likely related to short-term ET dynamics and the lack of information about bedrock characteristics and an on-site drainage system in the uncalibrated model. In general, simulation performance was better for the SCE setups. The SCE-simulations had a higher inverse air entry parameter resulting in SWC dynamics in better correspondence with data than the ROS simulations during dry periods. This illustrates that small scale measurements of soil hydraulic parameters cannot be transferred to the larger scale and that interpolated 1D inverse parameter estimates result in an acceptable performance for the catchment.

Single-Carrier Frequency-Domain Equalization With Index Modulation

Motivated by the recent index modulation (IM) concept in the spatial, frequency, and space-time domains, we propose a novel broadband single-carrier (SC)-based IM (SC-IM) scheme as well as its low-complexity frequency-domain equalization (FDE) algorithm. The proposed FDE-aided SC-IM scheme outperforms the conventional FDE-aided SC scheme, while achieving a comparable low level of detection complexity. In addition, in order to reduce the inter-channel correlation arising from the activated symbol indices, we propose a symbol mapping algorithm, which further improves the achievable error-rate performance of the SC-IM scheme. Our simulation results demonstrate the performance advantage of the proposed FDE-aided SC-IM scheme over the conventional FDE-aided SC scheme.

Simple approximations of semialgebraic sets and their applications to control

Many uncertainty sets encountered in control systems analysis and design can be expressed in terms of semialgebraic sets, that is as the intersection of sets described by means of polynomial inequalities. Important examples are for instance the Schur and Hurwitz stability domains. These sets often have very complicated shapes (nonconvex, and even non-connected), which render difficult their manipulation. It is therefore of considerable importance to find simple-enough approximations of these sets, able to capture their main characteristics while maintaining a low level of complexity. For these reasons, in the past years several convex approximations, based for instance on hyperrectangles, polytopes, or ellipsoids have been proposed.In this work, we move a step further, and propose possibly nonconvex yet still simple approximations, based on a small volume polynomial superlevel set of a single positive polynomial of given degree. We show how these sets can be easily approximated by minimizing the L1 norm of the polynomial over the semialgebraic set, subject to positivity constraints. Intuitively, this corresponds to the trace minimization heuristic commonly encountered in minimum volume ellipsoid problems. From a computational viewpoint, we design a hierarchy of convex linear matrix inequality problems to generate these approximations, and we provide theoretically rigorous convergence results, in the sense that the hierarchy of outer approximations converges in volume (or, equivalently, almost everywhere and almost uniformly) to the original set.Finally, we show how the concept of polynomial superlevel set can be used to generate samples uniformly distributed on a given semialgebraic set. The efficiency of the proposed approach is demonstrated by different numerical examples.

The role of scientists in policy-making regarding agricultural biotechnology: From traditional to alternative views

Scientists have always played an important role in informing policy decisions. However, many controversial policy problems regarding science and technology, such as agricultural biotechnology, are often characterised by low value consensus and high level of complexity. In these circumstances various policy actors legitimate their policy preferences using science. In this article, we challenge the linear model of science and policy and argue that the stakeholder model of science in policy is more appropriate for governance of controversial policy problems regarding science and technology. We build our argument on available literature and empirical data from interviews and two online surveys. We choose agricultural biotechnology as the case study to illustrate scientists' perception about their role in policy-making. Our study illustrates that agricultural biotechnology scientists sympathise with the stakeholder model of science and policy. However, there is a gap between perceived ideal role for scientists in policy-making and the role, which these scientists actually take.

The Five-Factor model and job performance in low complexity jobs: A quantitative synthesis

This article presents the results of four primary studies that investigated the degree to which the Big Five personality dimensions predict job performance in occupations with a low level of job complexity. Job performance was assessed as overall job performance (OJP), task performance (TP), and contextual performance (CP). The results showed that conscientiousness and emotional stability proved to be predictors of the three performance measures. In addition, extroversion was a relevant predictor of OJP and TP, and agreeableness was a predictor of CP. Implications for the theory and practice of job performance and personnel selection are discussed.

Links between fish community structure and habitat complexity of a rocky reef in the Gulf of California threatened by development: Implications for mitigation measures

In reefs, fish distribution and community structure are strongly linked to habitat structure. The objective of this study was to develop a baseline of the attributes of a rocky reef fish community threatened by development and their possible relationship with habitat complexity in order to assess how predicted habitat modification would impact the fish community. In the study area, the construction of a tourist marina is planned as part of a residential area with a total size of 500 ha. The project includes the translocation of corals, infilling of reclamation areas by dredging, and floating docks, which is predicted to affect both benthic rugosity and the types of benthic cover. Using hierarchical clustering based on benthic substrate type and rugosity we defined three levels of habitat complexity (Low, Medium, High). The fish community at different levels of complexity was characterized in terms of species richness, abundance, diversity and dominance, and was classified into seven trophic groups. Transects with high habitat complexity featured the highest cover of dead coral with macroalgae (43.7% ± 2.3, mean ± SE) and live coral (21.0% ± 1.9). There were no significant differences in rugosity among the three levels of habitat complexity (ANOVA, F = 0.145, df = 2, p = 0.87). A total of 19,799 individuals belonging to 76 species were recorded over an area of 12,000 m2. The greatest mean density and species richness occurred at high habitat complexity, with 1229.7 (±202.7) individuals per 500 m2 and 64 species, respectively. Community structure was significantly different in richness and abundance between high and low levels of complexity (p < 0.05). It is expected that the benthic habitat will be modified mainly by dredging associated with the construction of reclamation areas and the translocation of benthic organisms (mostly corals), affecting the habitat variables associated with different levels of habitat complexity in our survey. Reducing habitat complexity as a result of development is predicted to lead to a loss of species richness and ecological functions. A better understanding of the influence of habitat complexity on reef organisms can help to predict the potential impacts of habitat degradation and develop appropriate mitigation measures. Based on the results, a number of measures are suggested to detect and mitigate the expected negative impacts of construction and operation of the marina.

Managing the Entanglement: Complexity Leadership in Public Sector Systems

AbstractComplexity in public sector systems requires leaders to balance the administrative practices necessary to be aligned and efficient in the management of routine challenges and the adaptive practices required to respond to dynamic circumstances. Conventional notions of leadership in the field of public administration do not fully explain the role of leadership in balancing the entanglement of formal, top‐down, administrative functions and informal, emergent, adaptive functions within public sector settings with different levels of complexity. Drawing on and extending existing complexity leadership constructs, this article explores how leadership is enacted over the duration of six urban regeneration projects representing high, medium, and low levels of project complexity. The article suggests that greater attention needs to be paid to the tensions inherent in enabling leadership if actors are to cope with the complex, collaborative, cross‐boundary, adaptive work in which they are increasingly engaged.

Students’ Ability in Free, Semi-Structured and Structured Problem Posing Situations

Problem posing is a new and inventive pedagogical approach in mathematics education. It has long been under the shadow of problem solving, until recently, when researchers started to realize its potentials, resulting in a fastgrowing recognition of the need to incorporate it into Mathematics classroom learning. Therefore, the purpose of this study was to identify students’ problem posing ability in free, semi-structured and structured problem posing situations. In addition, this study would also determine their view about problem posing. The sample consisted of twenty eight Form 2 secondary school students. Two instruments were used: The Mathematical Problem Posing Task and The Problem Posing Questionnaire. The results revealed that the students were capable of posing 63 solvable mathematical problems, out of which, 55 (87%) in the low level of complexity and 8 (13%) in the moderate level of complexity, within the problem posing tasks given. The result also revealed that, free problem posing situations are more demanding task compared to the semi-structured and structured problem posing situations. Besides, the findings also found that, students have positive views about problem posing. In conclusion, problem posing is a potential pedagogical approach that can be implemented realistically in Mathematics classrooms.

EMG-Torque Relation in Chronic Stroke: A Novel EMG Complexity Representation With a Linear Electrode Array.

This study examines the electromyogram (EMG)-torque relation for chronic stroke survivors using a novel EMG complexity representation. Ten stroke subjects performed a series of submaximal isometric elbow flexion tasks using their affected and contralateral arms, respectively, while a 20-channel linear electrode array was used to record surface EMG from the biceps brachii muscles. The sample entropy (SampEn) of surface EMG signals was calculated with both global and local tolerance schemes. A regression analysis was performed between SampEn of each channel's surface EMG and elbow flexion torque. It was found that a linear regression can be used to well describe the relation between surface EMG SampEn and the torque. Each channel's root mean square (RMS) amplitude of surface EMG signal in the different torque level was computed to determine the channel with the highest EMG amplitude. The slope of the regression (observed from the channel with the highest EMG amplitude) was smaller on the impaired side than on the nonimpaired side in 8 of the 10 subjects, regardless of the tolerance scheme (global or local) and the range of torques (full or matched range) used for comparison. The surface EMG signals from the channels above the estimated muscle innervation zones demonstrated significantly lower levels of complexity compared with other channels between innervation zones and muscle tendons. The study provides a novel point of view of the EMG-torque relation in the complexity domain, and reveals its alterations post stroke, which are associated with complex neural and muscular changes post stroke. The slope difference between channels with regard to innervation zones also confirms the relevance of electrode position in surface EMG analysis.

Design-manufacturing integration and manufacturing complexity

Purpose The purpose of this paper is to propose that the effectiveness of organizational design-manufacturing integration (ODMI) practices is contingent upon the degree of complexity of the manufacturing environment. The paper submits that the level of use of ODMI ought to match the level of complexity of the manufacturing environment. The paper puts forward the hypothesis that when a misfit occurs between ODMI and complexity (high use of ODMI practices in low complexity environments or low use of ODMI practices in high complexity environments) manufacturing operational performance declines. Design/methodology/approach The paper tests the hypothesis based on a survey database of 725 manufacturers from 21 countries. The measurement model was assessed with confirmatory factor analysis and the hypothesis was tested with linear regression. Findings A misfit between the level of ODMI use (job rotation and co-location) and manufacturing complexity (product and process complexity) has a negative effect on manufacturing operational performance dimensions of quality, delivery and flexibility. Post hoc analyses also suggest that firms that operate in different environments in what concerns the rate of change in process technologies suffer differentiated negative impacts of ODMI-complexity misfit. Research limitations/implications Future studies could extend this research to other dimensions of design-manufacturing integration, such as technological practices. Practical implications Manufacturers with high levels of complexity should invest strongly in ODMI practices. However, manufacturers with low levels of complexity should invest in these practices with caution since the expected payoffs may not outweigh the effort. Originality/value The study assesses fit as a simultaneous set of contingency factors, applying profile-deviation analysis to ODMI and operational performance relationships. By focusing on plant-level manufacturing complexity, this study complements existing studies of product development complexity which tend to focus on project-level complexity.

Human Target Localization Using Hough Transform and Doppler Processing

In this letter, a localization algorithm, which combines Hough transform and Doppler processing, is proposed for Doppler radar human sensing applications. The Hough transform is first applied to extract the interested target components and real-time estimate their instantaneous frequencies (IFs). Then, based on the IF estimation result, the target movement trajectories are synthesized by Doppler processing. To improve the detection accuracy and robustness, a generalized linear model is proposed for Hough transform, which can achieve highly dimensional frequency fitting to compensate the nonlinear error, meanwhile maintaining a low level of computational complexity for real-time processing. Experimental results are presented to illustrate the performance of the proposed algorithm.

Intra-patient Inter-metastatic Genetic Heterogeneity in Colorectal Cancer as a Key Determinant of Survival after Curative Liver Resection.

Chromosomal instability is a well-defined hallmark of tumor aggressiveness and metastatic progression in colorectal cancer. The magnitude of genetic heterogeneity among distinct liver metastases from the same patient at the copy number level, as well as its relationship with chemotherapy exposure and patient outcome, remains unknown. We performed high-resolution DNA copy number analyses of 134 liver metastatic deposits from 45 colorectal cancer patients to assess: (i) intra-patient inter-metastatic genetic heterogeneity using a heterogeneity score based on pair-wise genetic distances among tumor deposits; and (ii) genomic complexity, defined as the proportion of the genome harboring aberrant DNA copy numbers. Results were analyzed in relation to the patients’ clinical course; previous chemotherapy exposure and outcome after surgical resection of liver metastases. We observed substantial variation in the level of intra-patient inter-metastatic heterogeneity. Heterogeneity was not associated with the number of metastatic lesions or their genomic complexity. In metachronous disease, heterogeneity was higher in patients previously exposed to chemotherapy. Importantly, intra-patient inter-metastatic heterogeneity was a strong prognostic determinant, stronger than known clinicopathological prognostic parameters. Patients with a low level of heterogeneity (below the median level) had a three-year progression-free and overall survival rate of 23% and 66% respectively, versus 5% and 18% for patients with a high level (hazard ratio0.4, 95% confidence interval 0.2–0.8, P = 0.01; and hazard ratio0.3,95% confidence interval 0.1–0.7, P = 0.007). A low patient-wise level of genomic complexity (below 25%) was also a favorable prognostic factor; however, the prognostic association of intra-patient heterogeneity was independent of genomic complexity in multivariable analyses. In conclusion, intra-patient inter-metastatic genetic heterogeneity is a pronounced feature of metastatic colorectal cancer, and the strong prognostic association reinforces its clinical relevance and places it as a key feature to be explored in future patient cohorts.

The Language of Extremity

Using the linguistic software Linguistic Inquiry Word Count, we analyzed transcripts of group discussions of whether the words “under God” should be in the Pledge of Allegiance. We hypothesized that members with an extreme opinion would use less complex language and more you pronouns than other members. Furthermore, extreme members would have less influence when they used you pronouns or more complex language consistent with the illusion of understanding. Extreme members were more confident and perceived themselves as more knowledgeable, but they did not use less complex language than other members. When extreme members did use complex language, they were less influential. Extreme members used more you pronouns and use of you pronouns reduced their influence in the group. Groups containing at least one extreme member had a much lower level of complexity in their discourse than groups without extreme members. Results are situated within research in integrative complexity, illusion of understanding, and attitude extremity.

Piezoelectricity enhancement of P(VDF/TrFE) by X-ray irradiation

Organic electronics is becoming more and more important because the low level of fabrication and deposition complexity even at large scale makes it a good candidate for future low cost technological product development. P(VDF-TrFE) is a co-polymer of special interest due its ferroelectric property enabling usage in re-programmable non-volatile organic memory and magnetoelectric sensors. Piezo force microscopy (PFM) provides access to the technologically relevant ferroelectric polarisability and its remanent polarization via imaging of the piezoelectric property. Here we use PFM to show that piezoelectric response of a P(VDF-TrFE) film can be enhanced by up to 260 % after soft X-ray irradiation. This enhancement correlates with morphological change of part of the film, from amorphous to crystalline. An optimal irradiation dose is found above which the film gets eroded and the piezoelectric response gets lowered.