Laser beam machining of various materials has found wide applications in the industry due to its advantages of high-speed machining, no tool wear and no vibration, precision and accuracy, low cost of machining, etc. Investigations into the laser beam machining of uncommon alloy are still limited and more research is needed in this field. In this paper, an analysis of the laser beam machining of tungsten alloy was performed, for cutting and drilling machining processes. First, an experimental analysis of microhardness and microstructure on the laser-cut samples was performed, and then the numerical simulation of the laser beam drilling process and its experimental validation was carried out. The experiments were carried out on a tungsten alloy plate of two different thicknesses, 0.5 and 1 mm. No significant changes in the microhardness, nor in the microstructure characteristics in the heat-affected zone (HAZ), were observed for the cutting conditions considered. A two-dimensional axisymmetric mathematical model for the simulation of the laser beam drilling process is solved by a finite volume method. The model was validated by comparing numerical and experimental results in terms of the size of HAZ and the size and shape of the drilled hole. Experimental and numerical results showed that HAZ is larger in the 0.5-mm-thick plate than in the 1-mm-thick plate under the same drilling conditions. Good agreement was observed between the experimental and numerical results. The developed model improves the understanding of the physical phenomena of laser beam machining and allows the optimization of laser and process parameters.

Abstract We compared the impact of performing dual-task walking on gait quality and prefrontal cortical activation assessed by functional near-infrared spectroscopy (fNIRS). We hypothesized a greater increase in fNIRS averaged over the left prefrontal cortex during dual-task walking would be associated with a greater decrease in gait quality (increased step-time variability; decreased gait speed, cadence, smoothness, and adaptability). In older adults (n=60, 75±5.8 years, 57% female), we quantified the change in fNIRS and gait metrics from single-task walking (even surface) to walking with attentional (reciting every-other letter of the alphabet) and physical (uneven surface) dual-task challenges using four 15m repetitions of each task. Gait metrics were computed from a tri-axial accelerometer at the lower-back. Changes in fNIRS from single to dual-task walking were not associated with changes in gait quality for both attentional and physical challenges (Spearman correlations, all p>0.08). Variability in response across individuals may contribute to our findings.

Voltage–current characteristics of free burning arcs in SF6 and air have been known for decades. As the demand for an SF6-free solution is increasing, there is an accompanying need to determine arc parameters in the alternative gases. An unblown arc experiment has been established to determine the voltage–current characteristics of SF6 alternative gases, which have not yet been thoroughly studied. In this experiment, free burning arc measurements were performed in a number of gases under consideration of SF6 alternatives, including CO2 and mixtures of CO2/O2 with and without C4F7N or C5F10O additives at the concentrations of up to 10 %. Measurements were also performed in air and SF6 for comparison. Arc voltage was measured in each gas at pressures ranging from 1- to 5-bar absolute, and electrode separations ranging from 20 to $95 \mathrm {~mm}$ . Voltage–current characteristic measurements for air and SF6 show good agreement with previously published results. A linear relationship of the arc voltage to the arc length is shown as well as the fourth root dependence of the arc voltage on the gas pressure. It was shown that neither the O2 nor the fluorinated additives to CO2 have any significant influence on the voltage–current characteristic. The minimum arc voltage in all measured gases was slightly higher than in SF6, but the arc in SF6 was the least stable and had the highest elongations resulting in high-voltage peaks. The arc voltage in air had a similar minimum value to the CO2-based gases, but the arc was much more stable, resulting in lower effective voltage, especially at low currents.

Growing intelligent transportation systems demand a vehicular communication technology that can satisfy high requirements in terms of data rates, latency, reliability and number of connected devices. To evaluate the performance of such communication technology, real-world measurements are required for various channel conditions. Since vehicular measurement campaigns are expensive and time-consuming, a high-mobility environment poses enormous challenges for performance measurements. Using the existing technique of time-stretching the transmit signals, such experiments can be emulated through measurements at a single lower velocity by inducing effects caused by higher velocities. The existing time-stretching technique poses the problem of different channel estimation quality between the time-stretched and the original system. To ensure that the technique gives accurate results in practical systems, we adapt the pilot-based channel estimation scheme within the existing time-stretching technique. Furthermore, we evaluate the proposed channel estimation scheme through simulations and a high-speed vehicular channel measurement campaign at the center frequency of 2.55 GHz.

This article evaluates the role that the economic conditionality of the European Union (EU) toward the six Western Balkan countries may play in the transformation of these countries as a part of their EU accession process. The article is a case study of a temporary policy shift that occurred in 2014 in relation to conditions that Bosnia and Herzegovina must fulfill to qualify for opening negotiations on EU membership. It also aims to address what this shift has achieved for the Europeanization of Bosnia and Herzegovina and its progress towards EU accession. The shift, implemented via an economic plan called the Reform Agenda, was an attempt at Europeanization of the country’s economic policies that temporarily put aside the constitutional reform demands that had previously dominated the Europeanization discourse. After the first five years of the Reform Agenda, moderate gains primarily in the domain of economic development and fiscal stability were made; however, political fragmentation and nationalistic and secessionist ideas have prevented the reforms from making a stronger impact. Additionally, the lack of a defined desired outcome in terms of measurable economic reforms and the inadequate planning by the EU were not conducive to a more transformative impact.

Faculty of Technology, University of Tuzla, Tuzla, Bosnia and Herzegovina, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States, Faculty of Chemistry and Chemical Engineering, University of Maribor, Maribor, Slovenia, Swiss Federal Institute of Technology Lausanne, Lausanne, Switzerland, Sustainable Process Integration Laboratory—SPIL, NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology—VUT BRNO, Brno, Czechia, CanmetENERGY, Natural Resources Canada, Varennes, QC, Canada, School of Chemical Engineering, Dalian University of Technology, Dalian, China

Increasing demands for logistics services cause several challenges related to total costs and meeting global environmental requirements. Logistic operators make efforts to improve all logistic processes and the distribution chain system by optimizing distribution networks and transport routes. Also, using clean or renewable energy help to meet the above-mentioned requirements by using environmentally friendly means of transportation such as electric and hybrid vehicles. The replacement of conventional with electric vehicles provides numerous benefits for improving the efficiency of the distribution chain system. This process is part of the concept known as Green Logistics, which strives to minimize the environmental impact of the logistics network and delivery. This paper focuses on identification of indicators for evaluating the acceptability of replacing conventional vehicles with electric vehicles in the fleet of logistics operators. We propose an evaluation matrix based on key indicators such as total costs, eco score fleet rating, and range and energy supply of vehicles. We use these indicators to determine the advantages, challenges, and possibilities of introducing electric vehicles in the logistics operator’s fleet. Also, we conducted a multi-criteria analysis of replacing conventional with electric vehicles in the fleet of one logistics operator.

At the beginning of the 20th century, more than a thousand mosques originating from the Ottoman period (1463-1878) were recorded in Bosnia and Herzegovina. Some estimates point that the number currently is much smaller. The goal of this study is to establish a typological classification of historical forms that were developed in more than four centuries. The diversity of patterns comes from the mixed influences ranging from the developed Ottoman style to the local material conditions and regional building traditions. This study used a qualitative evaluation of many characteristic examples to identify prevalent features that point to different types and subtypes of mosques. The evaluation of various examples used both firsthand observation and the written sources that are readily available. Thirty-six historical domed mosques were founded in Bosnia and Herzegovina, and their architecture is essentially a reflection of the architectural pattern predominantly from the 16th-century classical repertoire. However, a significantly higher proportion of mosques have sloping roofs where they strongly suggest domestic influences. The paper defines distinctive roofed mosque types where common characteristics predominate. Certain variations from the standard show a clear need for flexibility, adaptability, or improvisation. The study shows that the fundamental concept of the Turkish single-unit mosque, which was developed in Anatolia beginning in the 12th century, underwent a broad interpretation in Bosnia and Herzegovina throughout the Ottoman period, as evidenced by a variety of distinct types of roofed mosques.

This paper uses a mutual-information maximization paradigm to optimize the voltage levels written to cells in a Flash memory. To enable low-latency, each page of Flash memory stores only one coded bit in each Flash memory cell. For example, three-level cell (TL) Flash has three bit channels, one for each of three pages, that together determine which of eight voltage levels are written to each cell. Each Flash page is required to store the same number of data bits, but the various bits stored in the cell typically do not have to provide the same mutual information. A modified version of dynamic-assignment Blahut-Arimoto (DAB) moves the constellation points and adjusts the probability mass function for each bit channel to increase the mutual information of a worst bit channel with the goal of each bit channel providing the same mutual information. The resulting constellation provides essentially the same mutual information to each page while negligibly reducing the mutual information of the overall constellation. The optimized constellations feature points that are neither equally spaced nor equally likely. However, modern shaping techniques such as probabilistic amplitude shaping can provide coded modulations that support such constellations.

Interactive Imitation Learning (IIL) is a branch of Imitation Learning (IL) where human feedback is provided intermittently during robot execution allowing an online improvement of the robot's behavior. In recent years, IIL has increasingly started to carve out its own space as a promising data-driven alternative for solving complex robotic tasks. The advantages of IIL are its data-efficient, as the human feedback guides the robot directly towards an improved behavior, and its robustness, as the distribution mismatch between the teacher and learner trajectories is minimized by providing feedback directly over the learner's trajectories. Nevertheless, despite the opportunities that IIL presents, its terminology, structure, and applicability are not clear nor unified in the literature, slowing down its development and, therefore, the research of innovative formulations and discoveries. In this article, we attempt to facilitate research in IIL and lower entry barriers for new practitioners by providing a survey of the field that unifies and structures it. In addition, we aim to raise awareness of its potential, what has been accomplished and what are still open research questions. We organize the most relevant works in IIL in terms of human-robot interaction (i.e., types of feedback), interfaces (i.e., means of providing feedback), learning (i.e., models learned from feedback and function approximators), user experience (i.e., human perception about the learning process), applications, and benchmarks. Furthermore, we analyze similarities and differences between IIL and RL, providing a discussion on how the concepts offline, online, off-policy and on-policy learning should be transferred to IIL from the RL literature. We particularly focus on robotic applications in the real world and discuss their implications, limitations, and promising future areas of research.