On the capability of wheeled mobile robots for heavy object manipulation considering dynamic stability constraints

In the current research, the maximum mass that can be transferred by a Wheeled Mobile Robot (WMR) equipped with a manipulator will be found. Once such a multibody system carries a heavy payload, it may turn-over. Thus, a very important problem of how to design the motion of the wheeled robot in order to prevent its turn-over or, in other words, to maintain its dynamical stability appears. The solution of this problem is the main focus of the present study. Toward the solution of the aforementioned problem, a pseudospectral approach, which is based on powerful direct optimization technique, will be utilized. To tackle the loss of postural stability during object manipulation, which may have potentially severe concerns, a proper dynamic stability margin measure will be exploited to superiorly estimate and remove the risk of fall. The stability constraints will appear as inequality constraints that will then be transcribed into an equality constraint to solve the problem. Using the provided direct search method, an algorithm will be suggested to find the maximal mass that can be manipulated by the considered robot. The obtained simulation results reveal the success of the provided novel methodology to assess the manipulation capability of the considered WMR while considering dynamic stability and actuator limitations.     

Data Services with uncertain and correlated semantics

Currently, a good portion of datasets on Internet are accessed through data services, where user’s queries are answered as a composition of multiple data services. Defining the semantics of data services is the first step towards automating their composition. An interesting approach to define the semantics of data services is by describing them as semantic views over a domain ontology. However, defining such semantic views cannot always be done with certainty, especially when the service’s returned data are too complex. In such case, a data service is associated with several possible semantic views. In addition, complex correlations may be present among these possible semantic views, mainly when data services encapsulate the same data sources. In this paper, we propose a probabilistic approach to model the semantic uncertainty of data services. Services along with their possible semantic views are represented in probabilistic service registry. The correlations among service semantics are modeled through a directed probabilistic graphical model (Bayesian network). Based on our modeling, we study the problem of compositing correlated data services to answer a user query, and propose an efficient method to compute the different possible compositions and their probabilities.     

NERA: A new and efficient RSU based authentication scheme for VANETs

Wireless Networks - In vehicular ad-hoc networks (VANETs), the correctness of a message requires authentication of the origin vehicle. In this paper, we introduce a novel authentication scheme for...     

Microbial and "de novo" transformation of dicarboxylic acids by three airborne fungi

Micro-organisms and organic compounds of biogenic or anthropogenic origins are important constituents of atmospheric aerosols, which are involved in atmospheric processes and climate change. In order to investigate the role of fungi and their metabolisation activity, we collected airborne fungi using a biosampler in an urban location of Montreal, Quebec, Canada (45 degrees 28' N, 73 degrees 45' E). After isolation on Sabouraud dextrose agar, we exposed isolated colonies to dicarboxylic acids (C(2)-C(7)), a major group of organic aerosols and monitored their growth. Depending on the acid, total fungi numbers varied from 35 (oxalic acid) to 180 CFU/mL (glutaric acid). Transformation kinetics of malonic acid, presumably the most abundant dicarboxylic acid, at concentrations of 0.25 and 1.00 mM for isolated airborne fungi belonging to the genera Aspergillus, Penicillium, Eupenicillium, and Thysanophora with the fastest transformation rate are presented. The initial concentration was halved within 4.5 and 11.4 days. Other collected fungi did not show a significant degradation and the malonic acid concentration remained unchanged (0.25 and 1.00 mM) within 20 days. Degradation of acid with formation of metabolites was followed using high performance liquid chromatography-ultraviolet detection (HPLC/UV) and gas chromatography-mass spectrometry (GC/MS), as well as monitoring of (13)C labelled malonic acid degradation with solid-state nuclear magnetic resonance spectroscopy (NMR). Using GC/MS we identified two processes driving chemical modifications of organic aerosol solutions: (I) formation of metabolites within several days, and (II) rapid release (< or =2 min) of organic molecules from fungal species upon the insertion of taxa in organic aerosol solutions. Metabolites included aromatic compounds and alcohols (e.g. trimethylbenzene and butanol). Potential atmospheric implications of our results are discussed.     

Thermal effects on wave propagation characteristics of rotating strain gradient temperature-dependent functionally graded nanoscale beams

In the present article, wave dispersion behavior of a temperature-dependent functionally graded (FG) nanobeam undergoing rotation subjected to thermal loading is investigated according to nonlocal strain gradient theory, in which the stress enumerates for both nonlocal stress field and the strain gradient stress field. Mori–Tanaka distribution model is considered to express the gradual variation of material properties across the thickness. The governing equations are derived as a function of axial force due to centrifugal stiffening and displacements by applying Hamilton’s principle according to Euler–Bernoulli beam theory. By applying an analytical solution, the dispersion relations of rotating FG nanobeam are obtained by solving an eigenvalue problem. Obviously, numerical results indicate that various parameters such as angular velocity, gradient index, temperature change, wave number, and nonlocality parameter have significant influences on the wave characteristics of rotating FG nanobeams. Hence, the results of this research can provide useful information for the next generation studies and accurate design of nanomachines including nanoscale molecular bearings and nanogears, etc.     

Dynamic mathematical modeling of a novel dual-type industrial ethylene oxide (EO) reactor

In this paper, the dynamic behavior of a novel dual-type industrial ethylene oxide reactor has been proposed with taking catalyst deactivation into account. The configuration of two catalyst beds instead of one single catalyst bed is developed for conversion of ethylene to ethylene oxide. In the first reactor which is an industrial fixed-bed water-cooled reactor, the feed gas is partly converted to ethylene oxide. This reactor functions at very high yield and at a higher than normal operating temperature. In the second converter, the reaction heat is used to preheat the feed gas to the first reactor and a milder temperature profile is observed. The potential possibilities of a two-stage catalyst bed system are analyzed using a 1D heterogeneous dynamic model to obtain necessary comparative estimates. A differential evolution (DE) algorithm is applied as an effective and robust method to optimize the reactors length ratio. The results obtained from the simulation demonstrate that there is a desirable catalyst temperature profile along the dual-type reactor (DR) compared with the conventional single-type reactor (SR). In this way, the catalysts are exposed to less extreme temperatures and thus, diminishing the catalyst deactivation via sintering. Results from this study provided beneficial information about the effects of reactors configuration on catalyst lifetime and ethylene oxide production rate simultaneously.     

6‐Hydroxybenzothiophene Ketones: Potent Inhibitors of 17β‐Hydroxysteroid Dehydrogenase Type 1 (17β‐HSD1) Owing to Favorable Molecule Geometry and Conformational Preorganization

The inhibition of 17β‐hydroxysteroid dehydrogenase type 1 (17β‐HSD1), which catalyzes the conversion of estrone into the potent estrogen receptor agonist estradiol (E2), is discussed as a novel therapeutic approach for the treatment of estrogen‐dependent diseases. Because the reduction of E2 would be basically limited to the target tissues, this approach is expected to cause fewer side effects than the currently employed antihormonal therapies. Recently, we reported on 6‐hydroxybenzothiazole ketones as a new class of 17β‐HSD1 inhibitors with a notable activity/selectivity profile. In an attempt to further optimize these parameters, we modified the benzothiazole core by a systematic bioisosteric replacement. Thus, we were able to identify a new 6‐hydroxybenzothiophene derivative that displayed stronger inhibition of 17β‐HSD1 (IC₅₀=13 nM ) and that was also more selective than a benzothiazole analog. Using ab initio calculations, we found that the higher potency of the 6‐hydroxybenzothiophene derivative was probably due to more favorable conformational preorganization of the scaffold for binding to the enzyme.     

Electromagnetic interference shielding effectiveness of hybrid multifunctional Fe3O4/carbon nanofiber composite

Electromagnetic interference shielding effectiveness (EMI SE) of multifunctional Fe₃O₄/carbon nanofiber composites in the X-band region (8.2–12.4 GHz) is studied. Here, we examine the contributing effects of various parameters such as Fe₃O₄ content, carbonization temperature and thickness on total shielding efficiency (SE_total) of different samples. The maximum EMI SE of 67.9 dB is obtained for composite of 5 wt.% Fe₃O₄ (0.7 mm thick) with the dominant shielding by absorption (SE_A) of electromagnetic radiation. The enhanced electromagnetic shielding performance of Fe₃O₄/carbon nanofiber composites is attributed to the increment of both magnetic and dielectric losses due to the incorporation of magnetite nanofiller (Fe₃O₄) in electrically conducting carbon nanofiber matrix as well as the specific nanofibrous structure of carbon nanofiber mats, which forms a higher aspect ratio structure with randomly aligned nanofibers. Furthermore, we prove that the addition of elastomeric polydimethylsiloxane (PDMS) as a coating for carbon nanofiber composite strengthens the composite structure without interfering with its electromagnetic shielding efficiency.     

ApoB (XbaI) polymorphism and lipid variation in Teharnian population

This study examines the association of XbaI apolipoprotein B polymorphism with lipid related variables in Tehran lipid and glucose study. 809 subjects from the TLGS population were selected, anthropometrical and biochemical factors were measured. A segment of the apo B gene in exon 26 was amplified by PCR and the polymorphism was revealed by RFLP using XbaI restriction enzyme. Allele frequencies obtained for X⁺ and X^? were 27.6 and 72.4%, respectively. Presence of the X⁺ allele was significantly associated with increased levels of total cholesterol (p 0.048), apolipoprotein B (p 0.018), and low‐density lipoprotein (p 0.022). The associations were significant even after adjustment for age, BMI, smoking, and history of diabetes. There are some relationships between the presence of different alleles of XbaI polymorphism with serum cholesterol, apoB, and LDL‐C concentration. These findings highlight the importance of variation in this gene on some lipid related factors levels.