The Art Gallery Problem is ∃ℝ-complete

The Art Gallery Problem (AGP) is a classic problem in computational geometry, introduced in 1973 by Victor Klee. Given a simple polygon 풫 and an integer k , the goal is to decide if there exists a set G of k guards within 풫 such that every point p ∈ 풫 is seen by at least one guard g ∈ G . Each guard corresponds to a point in the polygon 풫, and we say that a guard g sees a point p if the line segment pg is contained in 풫. We prove that the AGP is ∃ ℝ-complete, implying that (1) any system of polynomial equations over the real numbers can be encoded as an instance of the AGP, and (2) the AGP is not in the complexity class NP unless NP = ∃ ℝ. As a corollary of our construction, we prove that for any real algebraic number α, there is an instance of the AGP where one of the coordinates of the guards equals α in any guard set of minimum cardinality. That rules out many natural geometric approaches to the problem, as it shows that any approach based on constructing a finite set of candidate points for placing guards has to include points with coordinates being roots of polynomials with arbitrary degree. As an illustration of our techniques, we show that for every compact semi-algebraic set S ⊆ [0, 1] 2 , there exists a polygon with corners at rational coordinates such that for every p ∈ [0, 1] 2 , there is a set of guards of minimum cardinality containing p if and only if p ∈ S . In the ∃ ℝ-hardness proof for the AGP, we introduce a new ∃ ℝ-complete problem ETR-INV. We believe that this problem is of independent interest, as it has already been used to obtain ∃ ℝ-hardness proofs for other problems.

Cost-allocation problems for fuzzy agents in a fixed-tree network

Cost-allocation problems in a fixed network are concerned with distributing the costs for use by a group of clients who cooperate in order to reduce such costs. We work only with tree networks and we assume that a minimum cost spanning tree network has already been constructed and now we are interested in the maintenance costs. The classic problem supposes that each agent stays for the entire time in the same node of the network. This paper introduces cost-allocation problems in a fixed-tree network with a set of agents whose activity over the nodes is fuzzy. Agent’s needs to pay for each period of time may differ. Moreover, the agents do not always remain in the same node for each period. We propose the extension of a very well-known solution for these problems: Bird’s rule.

The Mediating Role of Age Productivity on Human Resources Development, Health Infrastructure, and Proverty Level

Poverty is a classic problem in many regions in Indonesia, including the Bengkulu Province. There are several causes of poverty case in Bengkulu, three of which are low human resources, inadequate rural health infrastructure, and less productive population with productive working age. The purpose of the study is to examine 1) the influence of human resources management, health infrastructure, and productive age partially on poverty in Bengkulu Province, and 2) the influence of human resources, health infrastructure respectively through mediation of productive age on poverty in Bengkulu Province. This study uses a quantitative descriptive approach using secondary data. The research population is all districts/cities in Bengkulu Province totalling 9 districts and 1 city in 2010 – 2019. This study uses saturated sampling. The data was then processed and analyzed using SEM-PLS. The results of the study show that human resources proxied by the Human Development Index (HDI) had a positive effect on the poverty level, health infrastructure had no effect on the poverty level, productive age had no effect on the poverty level, productive age was not a mediating variable between resources and the poverty level, so that cannot be used as a mediating variable, and productive age does not mediate the effect of health infrastructure on poverty levels in Bengkulu Province.

A model of service-learning implementation: case of Ukrainian Catholic University

Service-learning (SL) is a relatively new approach for the Ukrainian education system. The Ukrainian Catholic University (UCU) became the first in Ukraine to introduce it at the institutional level. The organization of this process requires a transparent methodology and algorithm for implementation. In this study, we consider the institutional performance of SL at UCU from the standpoint of innovation management in the educational process. The paper’s objective is to describe the SL model implementation at the UCU based on the analysis of the carried-out optimizing processes. The classic problem-based approach with interactive research and design-based research were applied to develop the model. Furthermore, the description of the results uses a process-oriented methodology as the most appropriate for the current and future research work. The success of the SL approach implementation is partly due to the technical part by which it is about the design of the work process and the internal culture of the HEI. The groups of stakeholders involved in designing and adopting the SL model and pedagogy are foundational in the applied case of the process-oriented methodology. The final goal was to identify the areas with the most significant opportunities for improvement when implementing SL in the HEI. The model of implementation of SL in the HEI, presented in this study, was created on the business process mapping principles and can be valuable for other educational institutions that want to implement this approach.

Solution of Navier-Stokes equations for fluids with magnetorheological compensation used in structures with energy dissipaters

The fixed-wall rectangular cavity flow problem is a classic problem that has been studied since the beginning of computational fluid mechanics. The present work aims to provide a numerical and computational solution of the Navier-Stokes equations using the finite difference method, applied to model the problem of a magnetorheological fluid in a rectangular cavity with a fixed wall in shock absorbers devices, used in civil structures that use energy dissipators.

The effect of repertoire, routinization and enacted complexity: Explaining task performance through patterns of action

We use pattern mining tools from computer science to engage a classic problem in organizational theory: the relation between routinization and task performance. We develop and operationalize new measures of two key characteristics of organizational routines: repertoire and routinization. Repertoire refers to the number of recognizable patterns in a routine, and routinization refers to the fraction of observed actions that fit those patterns. We use these measures to develop a novel theory that predicts task performance based on the size of repertoire, the degree of routinization, and enacted complexity. We test this theory in two settings that differ in their programmability: crisis management and invoice management. We find that repertoire and routinization are important determinants of task performance in both settings, but with opposite effects. In both settings, however, the effect of repertoire and routinization is mediated by enacted complexity. This theoretical contribution is enabled by the methodological innovation of pattern mining, which allows us to treat routines as a collection of sequential patterns or paths. This innovation also allows us to clarify the relation of routinization and complexity, which are often confused because the terms routine and routinization connote simplicity. We demonstrate that routinization and enacted complexity are distinct constructs, conceptually and empirically. It is possible to have a high degree of routinization and complex enactments that vary each time a task is performed. This is because enacted complexity depends on the repertoire of patterns and how those patterns are combined to enact a task.

Residual refinement for interactive skin lesion segmentation

Background Image segmentation is a difficult and classic problem. It has a wide range of applications, one of which is skin lesion segmentation. Numerous researchers have made great efforts to tackle the problem, yet there is still no universal method in various application domains. Results We propose a novel approach that combines a deep convolutional neural network with a grabcut-like user interaction to tackle the interactive skin lesion segmentation problem. Slightly deviating from grabcut user interaction, our method uses boxes and clicks. In addition, contrary to existing interactive segmentation algorithms that combine the initial segmentation task with the following refinement task, we explicitly separate these tasks by designing individual sub-networks. One network is SBox-Net, and the other is Click-Net. SBox-Net is a full-fledged segmentation network that is built upon a pre-trained, state-of-the-art segmentation model, while Click-Net is a simple yet powerful network that combines feature maps extracted from SBox-Net and user clicks to residually refine the mistakes made by SBox-Net. Extensive experiments on two public datasets, PH2 and ISIC, confirm the effectiveness of our approach. Conclusions We present an interactive two-stage pipeline method for skin lesion segmentation, which was demonstrated to be effective in comprehensive experiments.

Meningkatkan Pendapatan Melalui Daur Ulang Limbah Masyarakat

The problem of garbage is a classic problem that repeatedly faced by the surrounding residents, especially in the Village of Peace. Because of the amount and level of danger, waste, especially plastic waste composed of chemicals, is difficult to decompose so that it is dangerous for the environment, so it is necessary to process waste to turn plastic waste into something useful. Based on surveys in the peaceful village area, North Binjai people still mostly do not have a fixed income. The implementation of the results of plastic bottle waste treatment into liquid hand soap packaging products in Damai Village was carried out to raise awareness of residents and provide ideas on how to increase their income. In addition, it can minimize pollution, so that the residents of The Peace Village can be more concerned about environmental cleanliness. The methods used in the program of utilizing plastic waste as packaging products are divided into two, namely the stage of exposure or explanation and the stage of practice to the community. Through training and mentoring the manufacture of hand washing soap and the utilization of plastic bottle waste, residents get insight into business opportunities that can be created through these creative ideas, and residents are already able to make liquid hand soap that can be sold. Through the training program on making hand soap in Damai Village, it is hoped that it can be an alternative to the use of plastic bottle waste which can be a product that can help improve the economy of the surrounding community.

Peningkatan Pengetahuan Masyarakat Kotagede dalam Pengelolaan Sampah Organik

Sampah merupakan permasalahan klasik yang belum terpecahkan dengan baik. Kesadaran masyarakat terhadap pengelolaan sampah masih rendah, termasuk dalam pengelolaan sampah organik. Daerah perkotaan, umumnya menjadi penyumbang sampah terbesar. Studi ini dilakukan untuk mengetahui tingkat pengetahuan masyarakat Kotagede terhadap pengelolaan sampah organik. Sasaran studi adalah anggota Muhammadiyah di lingkup PCM Kotagede. Metode studi yang digunakan adalah metode survei. Pelaksanaan survei dilakukan sebelum dan setelah dilaksanakan penyuluhan tentang peningkatan nilai ekonomi sampah organik. Survei dilakukan terhadap 55 orang peserta penyuluhan Upaya Peningkatan Nilai Ekonomi Sampah Organik. Hasil survei sebelum dilaksanakannya penyuluhan, 100% peserta mengetahui bahwa sampah organik dapat diolah kembali. Dari proses pengolahan sampah tersebut terdapat 23 orang (42%) responden paham tentang pengolahan sampah. Setelah penyuluhan dilaksanakan, sebanyak 84% paham tentang proses pengolahan sampah, sedangkan 16% belum memahami. Dari hasil tersebut, semua peserta menghendaki dilakukannya pengelolaan sampah organik yaitu dengan praktek pembuatan pupuk organik.Increasing Knowledge of the Kotagede CommunityIn Organic Waste ManagementABSTRACTGarbage is a classic problem that has not been resolved properly. Public awareness of waste management is still low, including in organic waste management. Urban areas are generally the largest contributor to waste. This study was conducted to determine the level of knowledge of the Kotagede community on organic waste management. The target of the study is Muhammadiyah members within the PCM Kotagede. The study method used was a survey method. The survey was carried out before and after counseling on the increase in the economic value of organic waste. The survey was conducted on 55 participants of counseling on Efforts to Increase the Economic Value of Organic Waste. From the survey results before the implementation of counseling, 100% of the participants knew that organic waste could be recycled. From the waste processing process, 23 people (42%) of respondents understand about waste processing. After counseling was carried out, as many as 84% understood about the waste processing process, while 16% did not understand. From these results, all participants wanted organic waste management to be carried out by practicing organic fertilizer production. Keywords: Economic; compost; MPM Kotagede; Garbage

The Passionate Beliefs. A Defense of the Cognitive-Evaluative Theory of Emotions

The philosophy of emotions has long been dominated by the view called «cognitivism». According to it, emotions are characterized (and definable) not by mere physical impulses but by a cognitive evaluation of their object. However, despite their success, cognitive theories have to deal with various objections and are divided on how to answer to them. In this essay I want to defend the form of cognitivism claimed by Martha Nussbaum from the most common criticisms. After a brief summary of her account, I confront some of the objections that have been raised against it. In Section 2 I deal with the classic problem of emotions in infants and animals, which lack linguistic abilities. Later, I confront the potential problem represented by cases in which one’s emotion and reasoned judgment seem to differ: in paragraph 3 I consider irrational phobias and fears, to show how they can be accounted for in terms of judgments and thoughts, and not only of perceptions; in paragraph 4 I deal with the objection that «judgementalist» theories (that is, those that describe emotions in terms of judgments and beliefs) violate the «principle of charity», for they ascribe an excessive irrationality to people. I argue that experimental evidence suggest that it is not implausible to assume that people have contradictory beliefs under conditions of uncertainty, and that perceptual theories of emotion (which compare emotional conflicts to optical illusions) fail to account for some fundamental aspects of these phenomena. Finally, in paragraph 5, I deal with the objection according to which a cognitive-evaluative theory cannot explain the sense of passivity that we commonly experience in emotions.