Natural Constraints Research Articles

Visual and haptic cues in processing occlusion.

Although shape is effective in processing occlusion, ambiguities in segmentation can also be addressed using depth discontinuity given visually and haptically. This study elucidates the contribution of visual and haptic cues to depth discontinuity in processing occlusion. A virtual reality experiment was conducted with 15 students as participants. Word stimuli were presented on a head-mounted display for recognition. The central part of the words was masked with a virtual ribbon placed at different depths so that the ribbon appeared as an occlusion. The visual depth cue was either present with binocular stereopsis or absent with monocular presentation. The haptic cue was either missing, provided consecutively, or concurrently, by actively tracing a real off-screen bar edge that was positionally aligned with the ribbon in the virtual space. Recognition performance was compared between depth cue conditions. We found that word recognition was better with the stereoscopic cue but not with the haptic cue, although both cues contributed to greater confidence in depth estimation. The performance was better when the ribbon was at the farther depth plane to appear as a hollow, rather than when it was at the nearer depth plane to cover the word. The results indicate that occlusion is processed in the human brain by visual input only despite the apparent effectiveness of haptic space perception, reflecting a complex set of natural constraints.

Logistics Village Location with Capacity Planning Problem, an MILP Model Approach

The optimal location for establishing logistics centers is of great importance in reducing logistics costs and improving supply chain efficiency. This paper aims to provide a conceptual framework for finding the optimal location and capacity for a logistics village establishment using mixed-integer linear programming (MILP). The proposed model is applied on Qazvin province, Iran, as a developing country with a strategic location in international transport corridors. Unlike previous research, the proposed approach considers various logistics operations such as warehousing, refrigeration, sorting, and packaging, along with their capacities as distinct decision variables. The study area is divided into 6972 blocks of 1.5 × 1.5 km, of which 59% are infeasible and excluded due to environmental and natural hazard constraints. The MILP model is then applied in the GAMS for each feasible block to identify the best alternatives for the logistic village establishment with maximum total profit. Based on the results, total freight imported to Qazvin province is directly transferred to their final destinations without visiting the logistics village, while around 98% of exports of Qazvin province would first enter the logistics village to get a service before delivering to customers.

Adaptive Constrained Formation-Tracking Control for a Tractor-Trailer Mobile Robot Team With Multiple Constraints

A team of multiple tractor–trailer mobile robots has many applications in areas including agriculture, logistics, transportation, etc. In this article, we propose a novel adaptive constrained formation-tracking control algorithm for the trailers in a tractor–trailer mobile robot team to track a desired formation, while satisfying multiple <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">precision</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">safety</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">feasibility</i> constraint requirements during the operation. Both universal barrier function approaches and a novel state transformation scheme are incorporated to deal with constraints of different nature. Adaptive estimators are introduced to estimate the rate of change of the desired trajectories for all trailers. We show that exponential convergence to a small neighborhood of the equilibrium can be guaranteed. In the end, a MATLAB simulation example and a Gazebo simulator study further demonstrate the efficacy of the proposed algorithm.

Study of the Sustainability of Potato Farms in the Region of Oued Souf (Southern Algeria)

The objective of this study is to diagnose the potato sector in the El Oued region by highlighting the technical and environmental situation of this sector. For this purpose, a field survey was carried out at the level of 75 farms in the El Oued region. The Oued Souf region’s Farm Sustainability Indicator (IDEA) is important. The assessment of agro-ecological, socio-territorial and economic indicators indicates that the agro-ecological indicator is the most represented by (the indicator of fertilizer and agricultural practices) by 98 out of 100. The results of this study show that this crop presents a good adaptation to the conditions of the region. This sector is undergoing significant development and is of great importance because this agricultural activity represents an economic potential at the local, regional and national levels. However, this sector remains fragile in relation to various constraints of a technical nature (unreasonable irrigation and fertilization and high seed prices), economic (price fluctuations and disorganized markets) and environmental (diseases, weeds) which directly influence the functioning of farms and therefore their profitability. This is why it is necessary to face the problems encountered and fight against the factors that can hinder the sustainability of this sector and give a competitive value.

Bank concentration, urban development and firm access to credit in Latin America

We study the effects of urban characteristics on access to commercial credit. For that purpose, we construct a dataset about the development potential of land in different cities, which takes into account building density, as well as natural geographic constraints. We use these data to assess how the development potential of urban centers affects the impact of bank concentration on financing. We apply our method to Latin America, a region in which banks play a crucial role, and many loans require real estate collateral. In line with the information-based hypothesis, we find a positive relation between bank concentration and firms’ credit accessibility; and we show that the development potential of the cities in which firms are located moderates this positive relationship and helps to explain firm-level differences in access to capital.

Mediterranean Diet: The Role of Phenolic Compounds from Aromatic Plant Foods

Today's global food system aggravates climate change while failing in meeting SDG2 and more. Yet, some sustainable food cultures, such as the Mediterranean Diet (MD), are simultaneously safe, healthy, and rooted in biodiversity. Their wide range of fruits, herbs, and vegetables convey many bioactive compounds, often associated with colour, texture, and aroma. Phenolic compounds are largely responsible for such features of MD's foods. These plant secondary metabolites all share in vitro bioactivities (e.g., antioxidants), and some are evidenced in vivo (e.g., plant sterols lower cholesterol levels in blood). The present work examines the role of polyphenols in the MD, with respect to human and planetary health. Since the commercial interest in polyphenols is increasing, a strategy for the sustainable exploitation of Mediterranean plants is essential in preserving species at risk while valuing local cultivars (e.g., through the geographical indication mechanism). Finally, the linkage of food habits with cultural landscapes, a cornerstone of the MD, should enable awareness-raising about seasonality, endemism, and other natural constraints to ensure the sustainable exploitation of Mediterranean plants.

Calabi–Yau metrics with conical singularities along line arrangements

Given a finite collection of lines $L_j \subset \mathbb{CP}^2$ together with real numbers $0 \lt \beta_j \lt 1$ satisfying natural constraint conditions, we show the existence of a Ricci–flat Kähler metric $g_{RF}$ with cone angle $2\pi\beta_j$ along each line $L_j$ asymptotic to a polyhedral Kähler cone at each multiple point. Moreover, we discuss a Chern–Weil formula that expresses the energy of $g_{RF}$ as a logarithmic Euler characteristic with points weighted according to the volume density of the metric.

Simultaneous p-adic Diophantine approximation

AbstractThe aim of this paper is to develop the theory of weighted Diophantine approximation of rational numbers to p-adic numbers. Firstly, we establish complete analogues of Khintchine’s theorem, the Duffin–Schaeffer theorem and the Jarník–Besicovitch theorem for ‘weighted’ simultaneous Diophantine approximation in the p-adic case. Secondly, we obtain a lower bound for the Hausdorff dimension of weighted simultaneously approximable points lying on p-adic manifolds. This is valid for very general classes of curves and manifolds and have natural constraints on the exponents of approximation. The key tools we use in our proofs are the Mass Transference Principle, including its recent extension due to Wang and Wu in 2019, and a Zero-One law for weighted p-adic approximations established in this paper.

Learning from parents and friends: The influence of intergenerational effect and peer effect on farmers' straw return

Straw returning to the field is considered a sustainable agricultural production mode that can be applied on a large scale. However, Straw returning to the field of Chinese farmers has the characteristics of “high willingness, low behavior”. Based on the survey data of 540 farmers in the main rice-producing areas of Sichuan Province, from the perspective of the social network, this study theoretically analyzed the impact of the two most important roles in the farmers' social network - parents and friends, that is, intergenerational effect and peer effect on farmers' straw returning. The probit model was used for empirical testing, and further discussed the difference between the two effects under different natural resource endowment constraints. The results showed that: (1) Among the sample farmers, 61.5% of them used straw returning. (2) The intergenerational effect has an inhibitory effect on the straw returning to the field, and the peer effect has a promoting effect on the straw returning to the field, and the effect of the peer effect is greater than that of the intergenerational effect. (3) Under the constraints of natural resource endowments such as land topography, land area, and home location, the influence of generational effect and peer effect on straw return was different for different farmers. The findings of the study can help improve the policy of integrated straw utilization and promote cleaner rice production.

Are Human Learners Capable of Learning Arbitrary Language Structures

The artificial grammar learning paradigm is a classic method of investigating the influence of universal constraints on shaping learning biases on language acquisition. While this method has been used extensively by linguists to test theoretical claims in generative grammar, one of the most prevalent frameworks in language acquisition, several studies have questioned whether artificial grammar learning reflects language acquisition enough to allow us to use it to draw inferences about the validity of universal constraints, particularly those arising from phonetic naturalness. The current study tests whether artificial grammar learning shows the effect of one robust phonetic naturalness constraint: the restriction on nasal harmony patterns arising from the sonority hierarchy. Nasal harmony is of particular interest because it is one of the few types of harmony that occurs between consonants and vowels, which is an under-researched topic. The results, contrary to the skeptical concerns, showed that participants (n = 120) could learn an artificial grammar involving a natural pattern, but could not learn one corresponding to an arbitrary/phonetically unmotivated pattern in the same way or to the same degree. This study contributes epistemic support to the large body of work using artificial grammar experiments to test phonological operations.

Autonomous trajectory planning for multi-stage launch vehicles using mass-projection sequential penalized convex relaxation method

Autonomous trajectory planning for multi-stage launch vehicles poses great technical challenges, mainly because of the highly nonlinear flight dynamics and complex multi-phase structure. Here, this problem is solved by a novel, robust, and efficient approach within the framework of convex optimization. Focusing on the multi-phase difficulty, a mass-projection technique that substitutes the original time independent variable with the mass history is introduced to eliminate the problem’s discontinuous nature and phase-linkage event constraints, then a new sequential relaxation-and-penalization method is proposed to address the resulting problem. All non-convex terms involved in the problem are relaxed to formulate a certainly feasible semi-definite problem, the deviation between which and the true problem is penalized by blending the information from the trust region and semi-definite constraint. The combination of the mass-projection technique and the sequential relaxation-and-penalization method is found to be capable of recovering the original problem and providing the optimal solution rapidly and reliably. Three representative simulations are performed to verify the robustness and computational efficiency of the proposed approach, and comparative results show that it achieves a 100% success rate for all cases, while enabling a 69% to 98% saving of computational time compared to typical methods.

Anti-fracking mobilisation and the “ordinance movement” in Argentina

This paper presents a sociological and legal analysis of a mode of action – municipal regulations promulgation – within a legal repertoire of action employed by opponents to Vaca Muerta’s unconventional hydrocarbon formation exploitation using the technology known as hydraulic fracturing (fracking). The inductive approach favoured here (textual analysis and comparison of the ordinances, information collection through semi-structured interviews) seeks to demonstrate that the choice of such a mode of action responds, on the one hand, to structural constraints of a political-legal nature and, on the other, reflects an attempt to foster a biocentric turn that is rooted in reflexive activist practices.

A Supplemental Lighting Control Approach in Controlled Environment Agriculture to Reduce Peak Power Consumption

Global population growth requires efficient food production, especially with food security concerns due to natural resources limitation and climate constraints. Supplemental lighting is an effective means of increasing productivity in greenhouses. However, supplemental lighting electricity cost can be high, and systematic lighting strategies are required to reduce lighting electricity cost. Prior research has focused on minimizing electricity use or cost, while maintaining adequate crop growth. However, in addition to being charged for electricity consumption, US greenhouse growers also pay a demand charge that is based on the peak electricity use during a 15-min period within each billing cycle. This demand charge is in the same order of magnitude as the charge for the used electricity, but has been ignored in prior lighting optimization research. This paper presents a lighting strategy for controlled environments (like greenhouses) equipped with dimmable light-emitting diodes (LEDs) to minimize supplemental lighting electricity cost and peak power consumption of supplemental lighting. Markov-based sunlight prediction is employed to develop a realistic control strategy and improve its efficiency. Moreover, the impact of shifting the time of day during which supplemental lighting is used on peak power consumption is investigated. Compared to a heuristic method, the proposed method illustrates an up to 51% mean peak reduction.

Algorithm for Determining the Purity of Pure Organic Phthalates by the Indirect Mass Balance Method

Pure organic substances are the first and key link in the chain of metrological traceability in organic analysis. In most cases, purity determination of the organic substance is a non-trivial task, the solution of which requires preliminary theoretical study and understanding of the capabilities of instrumental methods for developing a pertinent analytical procedure.Within the study, an algorithm for determining the purity of a separate group of organic compounds – ortho-phthalic acid esters (phthalates) was developed based on the mass balance model and the general algorithm for characterizing substances suitable for isolation or purification by distillation. An additional classification of probable impurities (into five types A – E) depending on their qualitative and quantitative characteristics is proposed, as well as suitable analytical methods for measuring impurities and confirming the identity of the main component are identified.The proposed algorithm was implemented on the State Primary Standard GET 208 to determine the purity of six priority phthalates: dimethyl phthalate, diethyl phthalate, di-(n-butyl) phthalate, benzyl butyl phthalate, di-(2-ethylhexyl) phthalate, and di-(n-octyl) phthalate. Certified pure phthalates were used to create a certified reference material for the composition of a solution of orthophthalic acid esters (phthalates) in methanol (6Ftlt-VNIIM) GSO 11366–2019.The study revealed that the adapted algorithm considers the specifics of work with the phthalates group and the features of the separation of probable impurities within the MB model, and is universal for all congeners of the group, but does not exclude the natural constraints of the mass balance method.

On the Optimal Shape and Efficiency Improvement of Fin Heat Sinks

In this paper, we analyze the values of the entropic efficiency of longitudinal fins by investigating the coupling between the function describing the fin profile and the corresponding steady-state temperature distribution along the fin. By starting from different boundary conditions, we look at the distribution temperature maximizing the efficiency of the fin. From this temperature distribution and by requesting that the fin must comply with natural physical constraints, such as the maximum fin thickness, we obtain an optimal profile for a purely convective fin and a convecting–radiating fin. For different boundary conditions and for a maximum fin thickness equal to four (in dimensionless units), both the profiles are increasing starting from the fin base until they reach the maximum value and then decrease to zero at the tip. Analytic and numerical results, together with different plots, are presented.

Free Vibration Characteristics of Bidirectional Graded Porous Plates with Elastic Foundations Using 2D-DQM

This manuscript develops for the first time a mathematical formulation of the dynamical behavior of bi-directional functionally graded porous plates (BDFGPP) resting on a Winkler–Pasternak foundation using unified higher-order plate theories (UHOPT). The kinematic displacement fields are exploited to fulfill the null shear strain/stress at the bottom and top surfaces of the plate without needing a shear factor correction. The bi-directional gradation of materials is proposed in the axial (x-axis) and transverse (z-axis) directions according to the power-law distribution function. The cosine function is employed to define the distribution of porosity through the transverse z-direction. Equations of motion in terms of displacements and associated boundary conditions are derived in detail using Hamilton’s principle. The two-dimensional differential integral quadrature method (2D-DIQM) is employed to transform partial differential equations of motion into a system of algebraic equations. Parametric analysis is performed to illustrate the effect of kinematic shear relations, gradation indices, porosity type, elastic foundations, geometrical dimensions, and boundary conditions (BCs) on natural frequencies and mode shapes of BDFGPP. The effect of the porosity coefficient on the natural frequency is dependent on the porosity type. The natural frequency is dependent on the coupling of gradation indices, boundary conditions, and shear distribution functions. The proposed model can be used in designing BDFGPP used in nuclear, marine, aerospace, and civil structures based on their topology and natural frequency constraints.

Parameter expansion for fitting regression models with non-negativity constraints

Regression models often require constraints that can be expressed as non-negativity constraints. This could be because it makes sense for the underlying modeling context, or it could be necessary to prevent the fitted values violating the natural constraints of the response distribution. Examples of the latter include log-link binomial regression and additive variance regression, while an example of the former is non-negative linear regression. Non-negativity constraints may apply directly to the regression parameters, in which case we call the model parameter-constrained, or they may apply to the linear predictor, in which case we call the model predictor-constrained. In this article, we show that it is possible to fit the predictor-constrained model using a parameter-constrained method applied to a model with additional dummy parameters, a technique called parameter expansion. This is advantageous because parameter-constrained models are often easier and more reliable to fit. After considering a range of models in which predictor-constrained estimation is desirable, we study the application of parameter expansion to a general regression model that includes the specific models as special cases. We then undertake a more in-depth study of parameter expansion for the log-link binomial model. Simulation results are presented demonstrating the computational advantages of parameter expansion.

An Enhanced Second-Order Cone Programming-Based Evaluation Method on Maximum Hosting Capacity of Solar Energy in Distribution Systems with Integrated Energy

In order to adjust to the change of the large-scale deployment of photovoltaic (PV) power generation and fully exploit the potentialities of an integrated energy distribution system (IEDS) in solar energy accommodation, an evaluation method on maximum hosting capacity of solar energy in IEDS based on convex relaxation optimization algorithm is proposed in this paper. Firstly, an evaluation model of maximum hosting capacity of solar energy for IEDS considering the electrical-thermal comprehensive utilization of solar energy is proposed, in which the maximization of PV capacity and solar collector (SC) capacity are fully considered. Secondly, IEDS’s potential in electricity, heat, and gas energy coordinated optimization is fully exploited to enhance the hosting capacity of solar energy in which the electric distribution network, heating network, and natural gas network constraints are fully modeled. Then, an enhanced second-order cone programming (SOCP)-based method is employed to solve the proposed maximum hosting capacity model. Through SOCP relaxation and linearization, the original nonconvex nonlinear programming model is converted into the mixed-integer second-order cone programming model. Meanwhile, to ensure the exactness of SOCP relaxation and improve the computation efficiency, increasingly tight linear cuts of distribution system and natural gas system are added to the SOCP relaxation. Finally, an example is given to verify the effectiveness of the proposed method. The analysis results show that the maximum hosting capacity of solar energy can be improved significantly by realizing the coordination of an integrated multi-energy system and the optimal utilization of electricity, heat, and gas energy. By applying SOCP relaxation, linearization, and adding increasingly tight linear cuts of distribution system and natural gas system to the SOCP relaxation, the proposed model can be solved accurately and efficiently.

Marine Vegetation Management Strategies: a framework for estuary wide prioritization of protection and rehabilitation

Intertidal systems are constrained by landscape morphology. Where these systems do occur, they often experience a wide range of anthropogenic impacts, further exacerbated by sea‐level rise (SLR). By mapping natural morphological constraints, anthropogenic impacts and modeled SLR, at an estuary‐wide scale the Marine Vegetation Management Strategies (MVMS) identify and prioritize sites and interventions that could address key threats and risks to the system enabling rehabilitation. Development of MVMS is part of an initiative within the broader New South Wales (NSW) state government's Marine Estate Management Strategy to deliver healthy coastal habitats. The MVMS are being developed to take a policy of “no net loss of key fish habitats” toward more active management of intertidal systems that maximize and sustain the ecosystem values and services. Spatial indicators were developed for a pilot estuary (Tweed River) to map and quantify “macrophyte potential” which is defined as the capacity for macrophytes (mangrove and saltmarsh) to deliver ecosystem services now and into the future (under scenarios of SLR). The approach incorporates datasets which indicate the geophysical nature of the landscape, anthropogenic exposure, and vulnerability to SLR. This strategic science‐based approach is being rolled out across coastal NSW, with the mapping products and associated resources identified as key tools to assist in the adopting of a more integrated approach to managing coastal wetlands.

Engineering enzyme activity using an expanded amino acid alphabet.

Enzyme design and engineering strategies are typically constrained by the limited size of nature's genetic alphabet, comprised of only 20 canonical amino acids. In recent years, site-selective incorporation of non-canonical amino acids (ncAAs) via an expanded genetic code has emerged as a powerful means of inserting new functional components into proteins, with hundreds of structurally diverse ncAAs now available. Here, we highlight how the emergence of an expanded repertoire of amino acids has opened new avenues in enzyme design and engineering. ncAAs have been used to probe complex biological mechanisms, augment enzyme function and, most ambitiously, embed new catalytic mechanisms into protein active sites that would be challenging to access within the constraints of nature's genetic code. We predict that the studies reviewed in this article, along with further advances in genetic code expansion technology, will establish ncAA incorporation as an increasingly important tool for biocatalysis in the coming years.