Micron-Level Actuators for Thermal Management of Microelectronic Devices

The failure rate of electronic equipment depends on the operating temperature. Although demand for more effective cooling of electronic devices has increased in the last decades because of the microminiaturization in device sizes accompanied by higher power dissipation levels, there is still a challenge for engineers to attain improved reliability of thermal management for intermediate and low-heat-flux systems. In the present study, an innovative alternative method is proposed and a computational parametric study has been conducted. A single microchip is placed in a two-dimensional channel. Different synthetic jet configurations are designed as actuators in order to investigate their effectiveness for thermal management. The effect is that the actuator enhances mixing by imparting momentum to the channel flow, thus manipulating the temperature field in a positive manner. The best control is achieved when the actuator is placed midway on the chip length and increasing the throat height. Also, using nozzle-like throat geometry increases the heat transfer rate from the microchip surface. Doubling the number of the actuators, optimally placing them, and phasing their membrane oscillations all improve the cooling.     

Short‐Fluorinated iCVD Coatings for Nonwetting Fabrics

Water repellency is often generated by taking advantage of surface textures and low surface energy coatings such as the one afforded by long perfluorinated side‐chains polymers. However, new regulations are phasing out these polymers because of their related health and safety hazard concerns. This is a particular challenge for water‐repellent fabrics as consumers expect safer products with stable performance and new functionalities. In this work, an approach is developed that allows for iCVD deposition of durable, conformal short fluorinated polymers stabilized with a crosslinking agent. As a result, high hydrophobicity and low liquid adhesion are achieved simultaneously while maintaining initial substrate breathability. It is explained why this polymeric coating—1H,1H‐perfluorooctyl methacrylate co divinylbenzene—exhibits remarkable hydrophobic properties amidst a wide range of other possible candidates. In order to further enhance the dynamic water repellency performance, the chemical treatment is combined with physical texturing—obtained through microsandblasting, a process particularly suitable for fabrics—thus making this combined approach a suitable candidate to meet the industrial needs. This work paves the way for the development of environmentally friendly, highly repellent coatings for large volume production and the application of roll‐to‐roll coating techniques, and multifunctionalization of fabrics and wearable devices.     

Enhancement of pacemaker induced stochastic resonance by an autapse in a scale-free neuronal network

An autapse is an unusual synapse that occurs between the axon and the soma of the same neuron. Mathematically, it can be described as a self-delayed feedback loop that is defined by a specific time-delay and the so-called autaptic coupling strength. Recently, the role and function of autapses within the nervous system has been studied extensively. Here, we extend the scope of theoretical research by investigating the effects of an autapse on the transmission of a weak localized pacemaker activity in a scale-free neuronal network. Our results reveal that by mediating the spiking activity of the pacemaker neuron, an autapse increases the propagation of its rhythm across the whole network, if only the autaptic time delay and the autaptic coupling strength are properly adjusted. We show that the autapse-induced enhancement of the transmission of pacemaker activity occurs only when the autaptic time delay is close to an integer multiple of the intrinsic oscillation time of the neurons that form the network. In particular, we demonstrate the emergence of multiple resonances involving the weak signal, the intrinsic oscillations, and the time scale that is dictated by the autapse. Interestingly, we also show that the enhancement of the pacemaker rhythm across the network is the strongest if the degree of the pacemaker neuron is lowest. This is because the dissipation of the localized rhythm is contained to the few directly linked neurons, and only afterwards, through the secondary neurons, it propagates further. If the pacemaker neuron has a high degree, then its rhythm is simply too weak to excite all the neighboring neurons, and propagation therefore fails.     

A segment-based approach to classify agricultural lands by using multi-temporal optical and microwave data

This research study aims to classify crop diversity in agricultural land with a segment-based approach using multi-temporal Kompsat-2 and Environmental Satellite (Envisat) advanced synthetic aperture radar (ASAR) data acquired in June, July and August on Karacabey Plain, Turkey. Analyses start with the image segmentation process applied to the fused optical images to search homogenous objects. The segmentation outputs are evaluated using multiple goodness measures, which take into consideration area and location similarities. Image classifications are performed on each multispectral (MS) single date image. In order to combine the most probable classes of the thematic maps, distance maps are generated. Evaluations of the thematic maps are performed through confusion matrices based on pixel-based and segment-based approaches. The results indicate that the highest overall accuracy of 88.71% and a kappa result of 0.86 are provided for the segment-based approach of the combined thematic map along with the microwave data, which is around 10% higher than the related pixel-based results.     

Dynamic Recrystallization Behavior of a Fe-Cr-Ni Super-Austenitic Stainless Steel

The super-austenitic stainless steels are extensively utilized in the seamless tubes production for oil extraction industries.Due to the importance of thermo-mechanical processing in the production of these tubes, the dynamic recrystallization(DRX)characteristics of a Cr-Ni super austenitic stainless steel(1.4563)were investigated in the present study.This was performed using the hot compression testing method in the temperature range of 950-1150-C and the strain rate of 10-3-10-1 s-1.The initiation and evo...     

Block polymers from poly(ethylene oxide) and styrene

Block copolymers containing poly(ethylene oxide) and polystyrene segments were synthesised via chemical reactions. A step-wise procedure was first employed to prepare peroxycarbamates which were later used to initiate free radical polymerization of styrene at elevated temperatures. In some runs the polymerization temperature and time were programmed. Styrene contents, molecular weights, elastic modulus—temperature relationships, impact strengths and stress—strain behaviour of the copolymers were determined.     

Yield and quality effects of electroplasmolysis and microwave applications on carrot juice production and storage

Electroplasmolysis as a pretreatment and microwave heating as an alternative to traditional heating were used in carrot juice production and the effects of these electrical methods on juice quality were investigated. Electroplasmolysis and microwave applications were optimized by response surface methodology. Optimum conditions were these: voltage gradient of 22.2 V/cm and treatment time of 60 s for electroplasmolysis, and flow rate of 90 mL/min with power of 900 W for microwave heating. Production of carrot juice was carried out by using these optimum conditions. After production, carrot juice samples were stored for 4 mo at +4 °C and analyses were performed at monthly intervals. As a result of electroplasmolysis, a 9.7% increase in juice yield was obtained. In addition, 100% pectin methylesterase inactivation was found with the microwave heating application. The results showed that the highest values for quality characteristics, such as antioxidant capacity and total pectin, total phenolic, and total carotenoid contents, were obtained with the combined applications of the electrical methods. In addition, these quality characteristics were protected better in the group of combined applications of the electrical methods (electroplasmolysis + microwave) during storage.     

A Route Towards Sustainability Through Engineered Polymeric Interfaces

Chemical vapor deposition (CVD) of polymer films represent the marriage of two of the most important technological innovations of the modern age. CVD as a mature technology for growing inorganic thin films is already a workhorse technology of the microfabrication industry and easily scalable from bench to plant. The low cost, mechanical flexibility, and varied functionality offered by polymer thin films make them attractive for both macro and micro scale applications. This review article focuses on two energy and resource efficient CVD polymerization methods, initiated Chemical Vapor Deposition (iCVD) and oxidative Chemical Vapor Deposition (oCVD). These solvent‐free, substrate independent techniques engineer multi‐scale, multi‐functional and conformal polymer thin film surfaces and interfaces for applications that can address the main sustainability challenges faced by the world today.