There are two main categories of force control schemes: hybrid position-force control and impedance control. However, the former does not take into account the dynamic interaction between the robot’s end effector and the environment. In contrast, impedance control includes regulation and stabilization of robot motion by creating a mathematical relationship between the interaction forces and the reference trajectories. It involves an energetic pair of a flow and an effort, instead of controlling a single position or a force. A mass-spring-damper impedance filter is generally used for safe interaction purposes. Tuning the parameters of the impedance filter is important and, if an unsuitable strategy is used, this can lead to unstable contact. Humans, however, have exceptionally effective control systems with advanced biological actuators. An individual can manipulate muscle stiffness to comply with the interaction forces. Accordingly, the parameters of the impedance filter should be time varying rather than value constant in order to match human behavior during interaction tasks. Therefore, this paper presents an overview of impedance control strategies including standard and extended control schemes. Standard controllers cover impedance and admittance architectures. Extended control schemes include admittance control with force tracking, variable impedance control, and impedance control of flexible joints. The categories of impedance control and their features and limitations are well introduced. Attention is paid to variable impedance control while considering the possible control schemes, the performance, stability, and the integration of constant compliant elements with the host robot.
Many studies have recommended implying the skills and strategies of creative thinking, critical thinking, and reflective thinking in EFLT curriculum to overcome EFL teaching-learning process difficulties. It is really necessary to make EFL teachers aware of the importance of cultural thinking and have a high perception of its forces. Culture of thinking consists of eight cultural forces in every learning situation; it helps to shape the group's cultural dynamic. These forces are expectations, language, time, modeling, opportunities, routines, interactions, and environment. This study aims to investigate EFL student-teachers’ perceptions of cultural thinking. The participants are selected randomly from the fourth-stage students at
... Show MoreBackground: the coronavirus leads to upper respiratory tract-associated manifestations like nasal congestion, sore throat, and smell disorder
Objectives: To reveal the impact of COVID-19 pandemic on otolaryngology symptoms using our daily medical practice.
Subject and Methods: A cross-sectional study that was carried on in the isolation wards at Al-Kindy and Al-Nu’man Teaching Hospitals during three months from the 1st of Jun. till the end of Aug. 2020. It included 1270 patients who were diagnosed with COVID-19 infection seen in the ENT consultation clinic and admitted to the isolation wards.
Results: Otolaryngological manifestations were shown
... Show MoreAn increasing interest is emerging in identifying natural products to overcome drug resistance in cancer patients. In this context, the present study was conducted to investigate the cytotoxic effects of neem plant (Azadirachta indica) oil in three different biological models (breast cancer cell lines, Allium cepa root tip, and mice vital organs). The cytotoxic potential of the neem oil was evaluated with two human cell lines (MCF7 and MDA-MB231) and an Allum cepa root tip bioassay. Histopathological analysis was conducted on the neem oil-treated and untreated control mice. The results revealed an anti-proliferative effect for neem oil on both estrogen receptor-positive (MCF7) and estrogen receptor-negative (MDA-MB231) breast cancer cell li
... Show MoreBacterial contamination of AL-Habania and AL-Tharthar reservoirs were studied during the period from February 2001 to January 2002, samples were collected from four stations in AL-Habania reservoir (AL-Warrar, AL-Theban regulator, middle of the reservoir and the fourth was towards AL-Razzaza reservoir) and from two stations at AL-Tharthar reservoir (Ein AL-Hilwa and the middle of the reservoir). Coliform bacteria, faecal Coliforms, Streptococci, faecal Streptococci and total count of bacteria were used as parameters of bacterial contamination in waters of both reservoirs through calculating the most probable number. Highest count of Coliform bacteria (15000 cell/100ml) was recorded at Ein AL-Hilwa and lowest count at AL-Theban regulator
... Show MoreIndirect electrochemical oxidation of phenol and its derivatives was investigated by using MnO2 rotating cylinder electrode. Taguchi experimental design method was employed to find the best conditions for the removal efficiency of phenol and its derivatives generated during the process. Two main parameters were investigated, current density (C.D.) and electrolysis time. The removal efficiency was considered as a response for the phenol and other organics removal. An orthogonal array L16, the signal to noise (S/N) ratio, and the analysis of variance were used to test the effect of designated process factors and their levels on the performance of phenol and other organics removal efficiency. The results showed that th
... Show MoreIn this paper, a study was made to determine the properties of Jovian radio bursts emitted at frequency 20.1MHZ. The data were provided from the Radio Jove archive for twelve years (2000-2012) for multi stations. The duration time for Long bursts (L) was (10-30) seconds and for Short bursts (S) was (10-20) seconds. The effect of radio bursts from the Sun and the galactic background were calculated at the same frequency and were found that radio bursts from the Sun will reduce the occurrence probability of Jovian radio bursts much more than radio bursts from the galactic background. The distribution of Jovian radio bursts was different; the occurrence probability with respect to the northern latitudes was more than the southern latitudes.
Zinc-air fuel cells (ZAFCs) are a promising energy source that could compete with lithium-ion batteries and perhaps proton-exchange membrane fuel cells (PEMFCs) for next-generation electrified transportation and energy storage applications. In the present work, a flow-type ZAFC with mechanical rechargeable was adopted, combined with an auxiliary cell (electrolyzer) for zinc renewal and electrolyte recharge to the main cell. In this work a practical study was performed to calculate the cell capacity (Ah), as well as study the electrolysis cell efficiency by current efficiency, and study the effective parameters that have an influence on cell performance such as space velocity and current density. The best parameters were selected to
... Show MoreThe main objective of this thesis is to study new concepts (up to our knowledge) which are P-rational submodules, P-polyform and fully polyform modules. We studied a special type of rational submodule, called the P-rational submodule. A submodule N of an R-module M is called P-rational (Simply, N≤_prM), if N is pure and Hom_R (M/N,E(M))=0 where E(M) is the injective hull of M. Many properties of the P-rational submodules were investigated, and various characteristics were given and discussed that are analogous to the results which are known in the concept of the rational submodule. We used a P-rational submodule to define a P-polyform module which is contained properly in the polyform module. An R-module M is called P-polyform if every es
... Show MoreThe world seen rapid developments in the field of information technology within all life fields, particularly the educational field. Usually, we find the traditional educational methods lack a sense of realism and interaction. Solving this problem is by utilizing virtual reality technology to make actual practice present in the classroom. As an interactive technology, it provides students with an accessible, reliable environment that was previously unavailable and offered an opportunity for learning by practicing instead of teacher-centered learning and within a vision that does not look at the past but looks to the future. Virtual reality technology will change the nature of the relationship between the teacher and the student. Thus, the c
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