Hopping conduction in (Ni,Co,Mn)O4 prepared by different synthetic routes: Conventional and spark plasma sintering

(Ni,Co,Mn)O₄ (NMC) oxides were prepared by conventional sintering (CS) and spark plasma sintering (SPS) using micro and nanopowders. Small hoping polaron theory was used in order to investigate effect of processing routes on electrical properties of NMC oxides as negative temperature coefficient (NTC) thermistors. Also, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques were utilized to analyze compositional and structural effects on the electrical properties of NMC compounds. Hopping conduction in NMC prepared by SPS and CS using nanopowder occurs via variable range hopping (VRH) mechanism, however conduction in NMC prepared by CS using micropowder follows nearest neighboring hopping (NNH) mode. Hopping distance and activation energy for the VRH mode were calculated using corresponding physical model.     

Development of EMA transducer for inspection of pipelines

Electromagnetic acoustic transducers (EMATs) have potential for In-line inspection (ILI) of pipelines compare to other Nondestructive evaluation (NDE) methods, since EMAT doesn’t need to contact and/or coupling material and can detect defects in outside of pipelines. However, improvement of transduction efficiency of EMATs is needed to secure integrity of the pipelines. To improve performance of EMAT, optimization of major parameters, such as strength of permanent magnet, shape of coil, configuration of static and dynamic magnetic fields is required. Thus, in this paper, investigation of transduction efficiency with variation of major parameters are performed by comparison of generated ultrasonic signals. Based on the investigation results, EMATs for ILI of pipelines are designed and fabricated with optimized Periodic solenoid array (PSA) types of meander-line sensor, static magnetic field, and then, performance of the developed EMATs are evaluated by detecting defects in the gas pipelines mounted in the one-bed testing system.     

MEA design for low water crossover in air-breathing DMFC

The water crossover behavior in air-breathing direct methanol fuel cell (DMFC) was studied with varying structural variables of membrane electrode assembly (MEA), such as existence of microporous layer (MPL) in cathode diffusion layer, hydrophobicity of cathode backing layer, and membrane thickness. Water crossover from anode to cathode was lowered by the introduction of MPL to cathode backing layer, the reduction of hydrophobicity of cathode backing layer, and the reduction of membrane thickness. To account for the observed water crossover behavior, water back flow caused by the hydraulic pressure difference between the cathode and anode was considered. It was also found that the methanol crossover was lowered with the reduction of water crossover. The MEA designed for low water crossover revealed improved stability under continuous operation.     

Implementation of a cost-effective home lighting control system on embedded Linux with OpenWrt

In recent years, the significance of greenhouses has been increased greatly because the world has been facing serious problems with energy as its growing demand. At the same time, home automation systems have been steadily gaining popularity; growing toward smart home based on Cloud technology. This paper introduces a cost-effective home energy saving system based on a small embedded system with remote controlling feature. For this purpose, the system is composed of a wireless router based on embedded Linux for the platform to develop a low-cost energy control server and a smart phone for remote light control app. The prototype system was implemented by porting OpenWrt onto the wireless router which is connected with an interface board with LEDs attached. The remote access and GUI function were implemented by TCP/IP programming using Apple iPhone. The operation of the remote control system was verified by socket communication between the smart phone and the wireless router, and by USB communication between the wireless router and the interface board. The implementation result shows that an OpenWrt-based wireless router can give benefits of saving energy and safety through lighting control.     

Dangerous Wi-Fi access point: attacks to benign smartphone applications

Personalization by means of third party application is one of the greatest advantages of smartphones. For example, when a user looks for a path to destination, he can download and install a navigation application with ease from official online market such as Google Play and Appstore. Such applications require an access to the Internet, and most users prefer Wi-Fi networks which are free to use, to mobile networks which cost a fee. For this reason, when they have no access to free Wi-Fi networks, most smartphone users choose to try to use unknown Wi-Fi access points (AP). However, this can be highly dangerous, because such unknown APs are sometimes installed by an adversary with malicious intentions such as stealing information or session hijacking. Today, smartphones contains all kinds of personal information of the users including e-mail address, passwords, schedules, business document, personal photographs, etc., making them an easy target for malicious users. If an adversary takes smartphone, he will get all of information of the users. For this reason, smartphone security has become very important today. In wireless environments, malicious users can easily eavesdrop on and intervene in communication between an end-user and the internet service providers, meaning more vulnerability to man-in-the-middle attacks. In this paper, we try to reveal the risk of using unknown APs by presenting demonstration results. The testbed is composed of two smartphones, two APs, and one server. The compromised AP forwards messages of victim smartphone to the fake server by using domain name system spoofing. Thus, the application that is running on the victim smartphone transfers HTTP request to the fake server. As a result, this application displays the abnormal pop-up advertisement, which contains malicious codes and links. Our demonstration shows that merely connecting to compromise APs can make a malicious behavior even the applications are benign.     

A power control technique for anti-collision schemes in RFID systems

The emerging technology of Radio Frequency IDentification (RFID) has enabled a wide range of automated tracking and monitoring applications. However, the process of interrogating a set of RFID tags usually involves sharing a wireless communication medium by an RFID reader and many tags. Tag collisions result in a significant delay to the interrogation process, and such collisions are hard to overcome because of the limited capabilities of passive RFID tags and their inability to sense the communication medium. While existing anti-collision schemes assume reading all tags at once which results in many collisions, we propose a novel approach in which the interrogation zone of an RFID reader is divided into a number of clusters (annuli), and tags of different clusters are read separately. Therefore, the likelihood of collisions is reduced as a result of reducing the number of tags that share the same channel at the same time.In this paper, we consider two optimization problems whose objective is minimizing the interrogation delay. The first one aims at finding the optimal clustering scheme assuming an ideal setting in which the transmission range of the RFID reader can be tuned with high precision. In the second one, we consider another scenario in which the RFID reader has a finite set of discrete transmission ranges. For each problem, we present a delay mathematical analysis and devise an algorithm to efficiently find the optimal number of clusters. The proposed approach can be integrated with any existing anti-collision scheme to improve its performance and, hence, meet the demand of large scale RFID applications. Simulation results show that our approach makes significant improvements in reducing collisions and delay.     

Development of user customized smart keyboard using Smart Product Design-Finite Element Analysis Process in the Internet of Things

In a hyper-connected society, IoT environment, markets are rapidly changing as smartphones penetrate global market. As smartphones are applied to various digital media, development of a novel smart product is required. In this paper, a Smart Product Design-Finite Element Analysis Process (SPD-FEAP) is developed to adopt fast-changing tends and user requirements that can be visually verified. The user requirements are derived and quantitatively evaluated from Smart Quality Function Deployment (SQFD) using WebData. Then the usage scenarios are created according to the priority of the functions derived from SQFD. 3D shape analysis by Finite Element Analysis (FEA) was conducted and printed out through Rapid Prototyping (RP) technology to identify any possible errors. Thus, a User Customized Smart Keyboard has been developed using SPD-FEAP.     

Efficient defect identification of soft failures induced by device local mismatch for nano-scale SRAM yield improvement

As the device size continues shrinking to nano-scale region, tiny defects induced device local mismatch in SRAM array becomes a major yield limiter. It is often quite time consuming and challenging to identify such kind of invisible defects through conventional FA techniques. This paper presents an efficient methodology on device local mismatch fault isolation with the combination of test features, advanced Electrical Failure Analysis (EFA) and Physical Failure Analysis (PFA) techniques. A successful case study involving this advanced methodology will be also discussed.     

Preparation and characterization of kaolin/starch foam

The objective of this work was to study the effect of the kaolin content on the properties of starch foams. The kaolin/starch foams were made with kaolin contents that ranged from 0 to 15 m% by baking in a hot mold. The starch and kaolin/starch foams were stored at room temperature with a relative humidity (RH) of 55% for 7 days prior to testing. An increase in the kaolin content increased the foam density. The izod impact strength increased up to 1151.37 J/m² at the highest kaolin content (15 m%). The improvement was about five times the izod impact strength of pure starch foam. Moreover, the presence of any kaolin reduced the water absorption ability of the starch foam. Scanning electron microscopy revealed that kaolin increased the size of the starch foam cells and was itself well dispersed. Kaolin/starch foams showed a higher thermal stability than pure starch foam.