Recognizing Visibility Graphs of Polygons with Holes and Internal-External Visibility Graphs of Polygons

Visibility graph of a polygon corresponds to its internal diagonals and boundary edges. For each vertex on the boundary of the polygon, we have a vertex in this graph and if two vertices of the polygon see each other there is an edge between their corresponding vertices in the graph. Two vertices of a polygon see each other if and only if their connecting line segment completely lies inside the polygon, and they are externally visible if and only if this line segment completely lies outside the polygon. Recognizing visibility graphs is the problem of deciding whether there is a simple polygon whose visibility graph is isomorphic to a given input graph. This problem is well-known and well-studied, but yet widely open in geometric graphs and computational geometry. Existential Theory of the Reals is the complexity class of problems that can be reduced to the problem of deciding whether there exists a solution to a quantifier-free formula F(X1,X2,...,Xn), involving equalities and inequalities of real polynomials with real variables. The complete problems for this complexity class are called Existential Theory of the Reals Complete. In this paper we show that recognizing visibility graphs of polygons with holes is Existential Theory of the Reals Complete. Moreover, we show that recognizing visibility graphs of simple polygons when we have the internal and external visibility graphs, is also Existential Theory of the Reals Complete.Comment: Sumbitted to COCOON2018 Conferenc

Evaluation of ports development degree in Bushehr province

Today, ports, as a communication bridge for the exchange of goods, play an important role in sea and land transport in creating integration in the post-colonial regions and establishing balance in the supply chain. In fact, each port has a different geographical location, equipment and function, and this has led to increased inequality in the development of ports and, by nature, cities and regions. The purpose of this study is to evaluate, identify and analyze the geographical facilities and capabilities of the ports of Bushehr province in order to develop the backward regions of this province. The research method in this research is descriptive-analytical using documentary sources, library. In order to weight and rank the criteria and sub-criteria, fuzzy AHP and TOPSIS models have been used. After a general review and comparison of criteria and sub-criteria, six ports of Bushehr, Assaluyeh, Kangan, Genaveh, Dayyer and Deylam in this province were selected from among the ports of Bushehr province which are located in the Persian Gulf. Findings show that Assaluyeh port is among the five ports compared in terms of criteria and sub-criteria in the first place. Therefore, it was selected as the most suitable port in the development of the southern regions of Bushehr province

Awareness of Ergonomics and its Relationship with the Prevalence of Musculoskeletal Disorders: a study on physiotherapists in Shiraz, Iran

Background: Ergonomics is a science dealing with human's physical and mental abilities and limitations, and inattention to this science leads to physical injuries among the staff and consequently affects the efficiency and productivity of the organisations. The aim of this study was to evaluate the awareness of Shiraz physiotherapists about ergonomics and its relation with the prevalence of their musculoskeletal disorders. Methods: This cross-sectional study was performed in 2015 on all physiotherapists working in Shiraz hospitals. Data were collected through a questionnaire about the awareness of ergonomics and analyzed through SPSS22 software package. Results: Mean age and work experience of the physiotherapists were respectively 34.06±8.5 and 9.38±7.45 years. Mean awareness of subjects about ergonomics principles, work conditions and the rate of occupational injuries and work problems were respectively 3.15 ± 0.5, 2.70 ± 0.52 and 1.80 ± 0.82 from 5. There was a significant relationship between awareness of ergonomics and musculoskeletal disorders (P=0.04). Increase in awareness of ergonomics was associated with decrease of the risk of musculoskeletal disorders (P=0.04, CI 95% =0.086-0.995, OR=0.259). Conclusion: The results show that increased awareness of ergonomics leads to musculoskeletal disorders reduction. Therefore, compiled educational programs can have a significant impact on learning about right body postures during work and can consequently reduce musculoskeletal disorders and occupational injuries and problems

Effect Assessment of Parkinson Disease on Default Mode Network of the Brain with ICA and SCA Methods in Resting State FMRI Data

Abstract Parkinson's disease (PD) is a progressive neurological disorder characterized by tremor, rigidity, and slowness of movements. Determining changes of spontaneous activity and connectivity of the brain is a critical step towards treatment of PD patients. Resting State functional Magnetic Resonance Imaging (RS-fMRI) is a non-invasive method that we use in this work to investigate changes of default mode network of the brain in PD. To this end, we apply two methods, Seed Correlation Analysis (SCA) and probabilistic independent Component Analysis (PICA). The results of advanced statistical group analysis on SCA values show that there is negative significant correlation between motor cortex and cerebellum in healthy, while this connection in PD is positive and not significant. This result implies the disturbance of equilibrium function of the brain in resting. Moreover, in both groups, there is significant positive correlation between areas located in basal ganglia. The results show that in healthy, there is not significant correlation between motor areas and basal ganglia, while in PD there are significant negative correlations between motor cortex and cerebellum with areas located in basal ganglia. The comparison of five ICs extracted by PICA showed lower DMN activation in basal ganglia. Finally, The result of our study show that the functional correlations between ROIs are more affected in PD than pattern maps of activity by PICA

Prevalence of Sick Building Syndrome (SBS) among Students and Teachers of Guidance Schools in Babol, Winter 2018

Background: It is important to determine the prevalence of Sick Building Syndrome (SBS) symptoms in school students and teachers, which is relevant to the physical environment of the building. The aim of this study was to determine the prevalence of sick building syndrome in students and teachers of guidance schools in Babol. Methods: This descriptive and analytical cross-sectional study was carried out in 15 guidance schools in Babol in the winter of 2018, among 150 students and 95 teachers. The MM040EA (Miljomedicine040) questionnaire was used to collect data and was completed by interview. Data were analyzed using Chi-square test. Results: Among the 12 symptoms of SBS, 50.7% of students had fatigue, and 44.7% had headaches. There was a significant correlation between heavy headedness (p = 0.42) and headache (p = 0.029) with students’ gender. There was a significant correlation between the teachers’ gender with the redness or dryness of facial skin (p = 0.015), redness or itching of hands (p = 0.009) and also fatigue (p = 0.003). There was a significant correlation between the symptoms of the SBS with very high temperature in the students (p = 0.050), and with the noises (p = 0.40) in the teachers. Conclusion: The present study showed that more than half of the students and teachers had symptoms of SBS. Since the symptoms of SBS are associated with some physical conditions of the classroom and school environment, the health condition of the schools should be annually checked for all aspects