A Facile, Fast, and Low-Cost Method for Fabrication of Micro/Nano-Textured Superhydrophobic Surfaces

Background Alkyl ketene dimer (AKD) is frequently used in paper industry as an inexpensive sizing agent. The formation of a fractal structure after curing the solidified AKD for an extra-long time (4 - 6 days) results in superhydrophobicity. In this study, a facile and low-cost method was utilized to turn AKD’s surface superhydrophobic in a very short period of time. Method We fabricated a superhydrophobic layer by dipping glass and paper substrates in molten AKD and then treating them with ethanol after solidification. The samples were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Confocal laser scanning microscopy, and dynamic contact angle goniometry. Results The results show that briefly treating the coatings, obtained from isothermally heated AKD melt at 40°C for 3 min, with ethanol leads to superhydrophobicity with an advancing and receding contact angle of 158.7±1.4° and 156.8±0.9°, respectively. By increasing the melt temperature to 70°C and heating time to 6 h followed by ethanol treatment, the advancing and receding contact angles increased to 163.7±1.3° and 162.6±1.2°, respectively. Conclusions This enhancement in superhydrophobicity is due to the formation of entangled irregular micro/nano textures that create air cushions on the surface resulting in droplet state transition from Wenzel to Cassie. In this method, ethanol can be used several times, and the energy consumption becomes very low. Based on the other techniques in this field, our method has eliminated the complex equipment and procedure applied in the fabrication of a superhydrophobic AKD.https://scholarscompass.vcu.edu/gradposters/1072/thumbnail.jp

Load balancing in cloud data centers with optimized virtual machines placement

So far, various solutions have been proposed for symmetric distribution of load cloud computing environments. In this article, a new solution to the optimal allocation of virtual machines in the cloud data centers is presented to provide a good load balancing among servers. The proposed method offers a solution uses learning automata as a reinforcement learning model to improve the performance of the optimization algorithm for optimal placement of virtual machines. Also, it helps the search algorithm to converge more quickly to the global optimum. The simulation results show the proposed method has been able to perform good level of load balancing in cloud data centers

Cocos Frillgoby, Bathygobius cocosensis (Bleeker, 1854): an additional fish element for the Iranian marine waters (Teleostei: Gobiidae)

Members of the pantropical/subtropical genus Bathygobius are small and common gobies in sheltered and exposed shallow rocky or sandy shorelines, reef crests, mangroves, seagrass beds, rock jetties and seawalls in the Atlantic and Indo-Pacific regions. This report documents a significant range extension of Cocos Frillgoby, Bathygobius cocosensis into the western parts of Indo-Pacific regions, in the Iranian intertidal coast of Makran Sea. The morphological description of collected individuals and its comparison with morphologically similar related goby species, B. meggitti is given and discussed

Qanat system, an ancient water management system in Iran: History, architectural design and fish diversity

Ancient Iran is one of the leading civilizations that actively appear to water resources management, especially by the invention of "Qanat", an artificial underground system/ subterranean tunnel-wells system where the water flows through gravity on a slight slope in arid and semi-arid regions at least 5000 years ago. Qanats were innovated in ancient Iran, spread throughout much of the Middle East, and extended into North Africa, Spain, Italy, and South Asia. Tools preparation, size selection, digging the first and deepest vertical shaft known as "mother-well", digging several other vertical shafts along a line between the mother-well and Qanat outlet, and constructing a horizontal connection between vertical shafts (known as the main tunnel), which guides the water out through an outlet, are the main steps in Qanat construction. By this innovation, Iranian solved their water-related problems using the basic concepts of Hydraulics. In the same way, water-related infrastructures were built using locally available materials to make a better life for humans and other wonderful well-designed and well-adapted organisms in dry and semi-dry regions, yielding great civilization with a simple, but a fantastic architecture that provides cold water in hot summer and warm water in cold winter. By means of these ancient underground structures, water was funneled from mountainous areas and aquifers to lower lands and thus alluvial fans could be opened up to settlement, and an agrarian civilization developed and evolved. In addition, Qanat provides a continual flow suitable for many aquatic organisms, including crabs, amphipods (gamarids), freshwater shrimps, and fishes. Qantas are home and refugia to about 42 fish species (36 native and 6 exotic species) belonging to 20 genera, 7 families, and 2 orders. The Qanat ichthyofauna is dominated by Cyprinidae with 19 species (45.2 %) followed by Leuciscidae and Nemacheilidae (6 species, 14.28% each), Poeciliidae and Aphaniidae (4 species, 9.52%), and Cobitidae (1 species 2.38%). It is about 14% of the total ichthyofauna of Iran. The Qanat ichthyofauna comprises 36 natives (including 20 endemics) and 6 exotic species. Qanat fauna dominates by species that are generally of small size, are broadcast spawners, nonmigratory, and have a wide tolerance of environmental conditions

Development of a Mobile Robot Local Navigation System Based on Fuzzy-Logic Control and Actual Virtual Target Switching

Robot local path planning in an unknown and changing environment with uncertainties is one of the most challenging problems in robotics which involves the integration of many different bodies of knowledge. This makes mobile robotics a challenge worldwide which for many years has been investigated by researchers. Therefore in this thesis, a new fuzzy logic control system is developed for reactive navigation of a behavior-based mobile robot. The motion of a Pioneer 3TM mobile robot was simulated to show the algorithm performance. The robot perceives its environment through an array of eight sonar range finders and self positioning-localization sensors. The robot environment consists of walls and dead end traps from any size and shape, as well as other stationary obstacles and it is assumed to be fully unknown. Robot behaviors consist of obstacle avoidance, target seeking, speed control, barrier following and local minimum avoidance. While the fuzzy logic body of the algorithm performs the main tasks of obstacle avoidance, target seeking, and speed adjustment, an actual-virtual target switch strategy integrated with the fuzzy logic algorithm enables the robot to show wall following behavior when needed. This combinational approach which uses a new kind of target shift, significantly results in resolving the problem of multiple minimum in local navigation which is an advantage beyond the pure fuzzy logic approach and the common virtual target switch techniques. In this work, multiple traps may have any type of shape or arrangement from barriers forming simple corners and U-shape dead ends to loops, maze, snail shape, and many others. Under the control of the algorithm, the mobile robot makes logical trajectories toward the target, finds best ways out of dead ends, avoids any types of obstacles, and adjusts its speed efficiently for better obstacle avoidance and according to power considerations and actual limits. From TRAINER Software and Colbert Program which were used in the simulation work, the system managed to solve all the problems in sample environments and the results were compared with results from other related methods to show the effectiveness and robustness of the proposed approach

A Novel Path Prediction Strategy for Tracking Intelligent Travelers

There are various technologies for positioning and tracking of intelligent travelers such as wireless local area networks (WLAN). However, the loss of actual positioning data is a common problem due to unexpected disconnection between tracking references and the traveler. Disconnection of the mobile terminal (MT) from the access points (AP) in WLAN-based systems is the example case of the problem. While enhancement of the physical system itself can reduce the risk of disconnections, complementary algorithms provide even more robustness in localization and tracking of the traveler. This research aims to develop a novel path prediction system which could keep track of the traveler during temporary shortage of actual positioning data. The system takes the advantage of the past trajectory information to compensate for the missing information during disconnections. A novel decision support system (DSS) is devised with the ability of learning decisional as well as kinematical behaviors of intelligent travelers. The system is then used in path prediction mode for reconstructing the missing parts of the trajectory when actual positioning data is unavailable. An ActivMedia Pioneer robot navigating under fuzzy artificial potential fields (APF) and blind-folded human subjects are the two types of intelligent travelers. The reactive motion of robots and path planning strategies of the blinds are similar in that both of them locally acquire knowledge and explore the space based on route-like spatial cognition. It is proposed and shown that route-like intelligent motion is based on a combination of decisional and kinematical factors. The system is designed in such a way to integrate these two types of motion factors using causal inference mechanism of the fuzzy cognitive map (FCM). The FCM nodes are a novel selection of kinematical factors. Genetic algorithm (GA) is then used to train the FCM to be able to replicate the decisional behaviors of the intelligent traveler. Experimental works show the capabilities of the developed DSS in human path prediction using both simulated and actual WLAN-based positioning dataset. Locational error is set to be limited to 1 m which is suitable for wireless tracking of human subjects with up to 10% improvement compared to the most related works. Both simulation and actual experiments were also carried out on the Pioneer platform. The accuracy in prediction of robot trajectory was obtained about 83% with considerable improvement compared to the recent methods. Apart from the positioning algorithm of this dissertation, there are several applications of this DSS to other areas including assistive technology for the blind and human-robot interaction

The Critical Role of Dynamic Surface Tension of Surfactants on The Impact Dynamics of Water Droplets

Due to their time-dependent surface tension, the addition of surface-active agents or surfactants to water for specific applications has made controlling the impact dynamics of these droplets a complex phenomenon. This work investigates the influence of the molecular weight, concentration, and ionic nature of the surfactants as well as the substrate surface characteristics on the impact dynamics of surfactant-laden droplets using a high-speed camera at 10000 frames per second. Sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, and n-decanoyl-n-methylglucamine were used as anionic, cationic, and nonionic surfactants, respectively. We used hydrophilic glass slides, hydrophobic polytetrafluoroethylene, and superhydrophobic alkyl ketene dimer (AKD) as substrates. The results show that the efficiency of the surfactant addition in increasing the maximum spreading diameter is significantly influenced by the molecular weight and ionic nature of the solutions as well as the nonwettability of the substrate. Among all of the surfaces examined, the concentration and ionic nature of the solutions were found to be more dominant parameters in determining the energy dissipation in the retraction phase of the droplet impact on the superhydrophobic AKD surfaces. As the concentration decreases or positive charges are present in the solution, it is more likely to observe a similar retraction dynamic to pure water when the droplet hits the superhydrophobic AKD having negatively charged surface sites. Finally, in terms of the impact outcomes of the surfactant-laden droplets on the superhydrophobic AKD, it is shown that the influence of the surfactant addition is more noticeable at lower Weber numbers, where the droplet tries to rebound by overcoming the energy loss that occurred in the spreading.https://scholarscompass.vcu.edu/gradposters/1126/thumbnail.jp

UGROŽENE VRSTE RIBA U SVIJETU: Aphanius farsicus Teimori, Esmaeili i Reichenbacher, 2011 (Cyprinodontidae)

Tooth-carp Aphanius farsicus Teimori, Esmaeili and Reichenbacher, 2011 (Cyprinodontidae), or Farsi endemic tooth-carp, was once common in the Maharloo Lake Basin (Fars), but is disappearing now from its native region. This fish has not been listed in IUCN Red Data Book even though it should be due to criteria such as restricted distribution, destruction of spawning grounds and environmental pollution and drought. This vulnerable species has considerable ecological importance, but there are little data on its biology. The limited available data on its systematics, distribution, ecology, reproduction and threats are summarized and discussed.Vrsta šaranozupke Aphanius farsicus Teimori (Esmaeili i Reichenbacher, 2011) iz porodice Cyprinodontidae ili endemična farska vrsta nekoć je bila česta u slivu jezera Maharloo, a danas nestaje iz autohtonog staništa. Ova vrsta šaranozupke još se ne nalazi na popisu IUCN-ove Crvene knjige ugroženih vrsta, iako zadovoljava sve kriterije za svrstavanje na spomenuti popis – ograničena joj je distribucija, mrijestilišna područja se razaraju, zagađuje se okoliš i javlja se suša. Ova osjetljiva vrsta ima veliku ekološku važnost, ali postoji malo podataka o njezinoj biologiji. U ovom članku iznose se i analiziraju ograničeni dostupni podaci o njezinoj sistematici, distribuciji, ekologiji, reprodukciji i prijetnjama koje joj ugrožavaju stanište

Gonad morphology and histology of an endemic tooth-carp, Aphanius sophiae (Heckel, 1847) from Iran

This study presents the first details on morphological and histological characteristics of gonads and gonadal development stages of an endemic tooth-carp, Aphanius sophiae (Heckel, 1847) from a spring-stream system (south of Iran). The sampling was done from March 2012 to March 2013 using dip net, and a total of 226 individuals were collected. The gonads of specimens were removed, and then fixed in 10% formalin solution after checking their morphology and measuring their weights, lengths and widths. Based on the size, shape and weight of the gonads, degree of occupation of the body cavity, presence or absence of ripe oocytes or milt, diameter of the oocytes in the ovary, and histological observations, five stages of sexual maturation in females and males were determined by macroscopic and microscopic criteria. The results of the gonadal stages indicated that A. sophiae spawns at the beginning of spring