On fiber diameters of continuous maps

We present a surprisingly short proof that for any continuous map $f : \mathbb{R}^n \rightarrow \mathbb{R}^m$, if $n>m$, then there exists no bound on the diameter of fibers of $f$. Moreover, we show that when $m=1$, the union of small fibers of $f$ is bounded; when $m>1$, the union of small fibers need not be bounded. Applications to data analysis are considered.Comment: 6 pages, 2 figure

Ergonomic Investigation of Occupational Drivers and Seat Design of Taxicabs in Nigeria

Repetitive trauma disorder and other work related musculoskeletal problems are prevalent among occupational drivers worldwide. This justifies the continue research and development efforts in the area of design of comfortable, safe and effective seat system by the automotive industry. The misfit seat variables are traceable to the difference between the adopted anthropometric measurement and that of the user population in the affected countries where the vehicle are exported. The objective of this paper is to investigate the ergonomic suitability of imported technological system specifically taxicab driver seat in Nigeria. Particular focus was placed to identify seat features that contribute to discomfort and work related MSDs of the operator. The application of participatory ergonomic intervention (PEI) approach is explored to achieve the objectives of this paper

Improved magic states distillation for quantum universality

Given stabilizer operations and the ability to repeatedly prepare a single-qubit mixed state rho, can we do universal quantum computation? As motivation for this question, "magic state" distillation procedures can reduce the general fault-tolerance problem to that of performing fault-tolerant stabilizer circuits. We improve the procedures of Bravyi and Kitaev in the Hadamard "magic" direction of the Bloch sphere to achieve a sharp threshold between those rho allowing universal quantum computation, and those for which any calculation can be efficiently classically simulated. As a corollary, the ability to repeatedly prepare any pure state which is not a stabilizer state (e.g., any single-qubit pure state which is not a Pauli eigenstate), together with stabilizer operations, gives quantum universality. It remains open whether there is also a tight separation in the so-called T direction.Comment: 6 pages, 5 figure

Optical Vortices during a Super-Resolution Process in a Metamaterial

We show that a super-resolution process with 100% visibility is characterized by the formation of a point of phase singularity in free space outside the lens in the form of a saddle with topological charge equal to -1. The saddle point is connected to two vortices at the end boundary of the lens, and the two vortices are in turn connected to another saddle point inside the lens. The structure saddle-vortices-saddle is topologically stable. The formation of the saddle point in free space explains also the negative flux of energy present in a certain region of space outside the lens. The circulation strength of the power flow can be controlled by varying the position of the object plane with respect to the lens

Practice of walking and its association with perceived environment among elderly Brazilians living in a region of low socioeconomic level

<p>Abstract</p> <p>Background</p> <p>The aim of this study was analyze associations between the practice of walking and environmental perception among elderly Brazilians in a region of low socioeconomic level.</p> <p>Methods</p> <p>A cross-sectional study was conducted among 385 elderly people aged 60 years and over. To evaluate walking, the International Physical Activity Questionnaire (IPAQ), long version (leisure and transport modules) was used. The environment was evaluated by means of the Neighborhood Environmental Walkability Scale (NEWS) (adapted Brazilian version). For the statistical analysis, multiple logistic regression models were created separately for men and women. The practice of at least 150 minutes a week of walking was the dependent variable, and the variables of environmental perception were the independent variables. All the models were controlled for schooling level and age.</p> <p>Results</p> <p>The proportion of elderly people active in walking was 56.9% for the men and 26.4% for the women. The perception of the presence of soccer fields (OR = 4.12) and their proximity, within ten minutes' walk from home (OR = 3.43), were associated with the practice of walking among the men. The perception of the presence of public squares (OR = 4.70) and the proximity of primary healthcare units, within ten minutes' walk from home (OR = 3.71), were associated with the practice of walking among the women. An association with adequate perception of vehicle traffic remained at the threshold of significance for the women.</p> <p>Conclusion</p> <p>Accessibility of leisure structures such as football fields and public squares and of health services such as primary healthcare units were important environmental variables associated with the practice of walking among elderly people living in a region of low socioeconomic level in Brazil. These variables need to be taken into consideration when aiming to promote the practice of walking among elderly people living in similar regions.</p

Towards a Formal Approach to Validating and Verifying Functional Design for Complex Safety Critical Systems

The quality and reliability of safety criticalsoftware systems are highly dependent on proper systemvalidation and verification. In model-driven softwaredevelopment, semi-formal notations are often used inrequirements capture. Though semi-formal notations possessadvantages, their major disadvantage is their imprecision. Atechnique to eliminate imprecision is to transform semi-formalmodels into an analyzable representation using formalspecification techniques (FSTs). With this approach to systemvalidation and verification, safety critical systems can bedeveloped more reliably. This work documents early experienceof applying FSTs on UML class diagrams as attributeconstraints, and pre- post-conditions on procedures. Thevalidation and verification of the requirements of a system tomonitor unmanned aerial vehicles in unrestricted airspace is theorigin of this work. The challenge is the development of a systemwith incomplete specifications; multiple conflicting stakeholders’interests; existence of a prototype system; the need forstandardized compliance, where validation and verification areparamount, which necessitates forward and reverse engineeringactivities

N-dimensional geometries and Einstein equations from systems of PDE's

The aim of the present work is twofold: first, we show how all the $n$-dimensional Riemannian and Lorentzian metrics can be constructed from a certain class of systems of second-order PDE's which are in duality to the Hamilton-Jacobi equation and second we impose the Einstein equations to these PDE's

Komunikasi Pendidikan melalui Pemanfaatan Media Pembelajaran Daring pada Masa Pandemi COVID-19 di Universitas Nusa Cendana

Pandemi COVID-19 memaksa Universitas Nusa Cendana (Undana) memberhentikan pembelajaran tatap muka dan menggantinya dengan pembelajaran daring. Penelitian ini bertujuan untuk menyelidiki pelaksanaan komunikasi pendidikan melalui pengembangan media pembelajaran daring pada masa pandemi COVID-19 di Undana. Penelitian ini menggunakan metode kualitatif dengan pendekatan studi kasus. Teknik pengumpulandata dilakukan dengan teknik wawancara mendalam bersama 48 orang, dengan rincian 11 dosen mewakili masing-masing fakultas dan 37 orang mewakili mahasiswa selanjutnya data yang terkumpul dianalisis menggunakan teknik analisis data model interaktif. Hasil penelitian menemukan bahwa media komunikasi pendidikan pada masa pandemi COVID-19 di Undana adalah aplikasi Google Meet, Zoom, Whatsapp, Telegram, Google Classroom karena lebih mudah dioperasikan dibanding e-learning Undana sebagai mediakomunikasi internal kampus. Penggunaan ragam aplikasi sebagai media pembelajaran di Undana menambah kerumitan proses belajar. Minimnya antusiasme mahasiswa, pemahaman dosen terhadap media pembelajaran serta belum meratanya akses jaringan internet di Provinsi NTT juga menjadi kendala tersendiri sehingga belum sejalan dengan pengimplementasian kurikulum “Merdeka Belajar Kampus Merdeka”. Penelitian inimemberikan kontribusi tentang komunikasi pendidikan melalui pengembangan media pembelajaran daring pada masa pandemi COVID-19 serta sebagai masukan bagi pembuat kebijakan di universitas terkait efektivitas pemanfaatan aplikasi e-learning sebagai sarana komunikasi pendidikan di Undana

Optimized broad-histogram simulations for strong first-order phase transitions: Droplet transitions in the large-Q Potts model

The numerical simulation of strongly first-order phase transitions has remained a notoriously difficult problem even for classical systems due to the exponentially suppressed (thermal) equilibration in the vicinity of such a transition. In the absence of efficient update techniques, a common approach to improve equilibration in Monte Carlo simulations is to broaden the sampled statistical ensemble beyond the bimodal distribution of the canonical ensemble. Here we show how a recently developed feedback algorithm can systematically optimize such broad-histogram ensembles and significantly speed up equilibration in comparison with other extended ensemble techniques such as flat-histogram, multicanonical or Wang-Landau sampling. As a prototypical example of a strong first-order transition we simulate the two-dimensional Potts model with up to Q=250 different states on large systems. The optimized histogram develops a distinct multipeak structure, thereby resolving entropic barriers and their associated phase transitions in the phase coexistence region such as droplet nucleation and annihilation or droplet-strip transitions for systems with periodic boundary conditions. We characterize the efficiency of the optimized histogram sampling by measuring round-trip times tau(N,Q) across the phase transition for samples of size N spins. While we find power-law scaling of tau vs. N for small Q \lesssim 50 and N \lesssim 40^2, we observe a crossover to exponential scaling for larger Q. These results demonstrate that despite the ensemble optimization broad-histogram simulations cannot fully eliminate the supercritical slowing down at strongly first-order transitions.Comment: 11 pages, 12 figure

challenges and insights for improving

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