Nitrogen recovery by urea hydrolysis and struvite precipitation from anthropogenic urine.

Human urine is a source of nutrients and has a significant potential for recycle of nitrogen. Recently, much research focused on separate collection and treatment of human urine. Recovery of nutrients from human urine requires hydrolysis of urea into ammonia and subsequent removal of ammonia and sometimes phosphorus. This study attempted to evaluate urea hydrolysis of human urine in both untreated fresh samples and urease added urine samples. Recovery of nutrients by struvite precipitation on pre-hydrolysed samples was also assessed on undiluted and 1:1 diluted samples. Results of urea hydrolysis on untreated urine samples indicated that the process was slow and pH exerted a significant effect on the process. No hydrolysis occurred above pH 10. From pH 2 to 7.5, 25% of urea could be hydrolysed in 30 d. Urease added hydrolysis with the enzyme doses 25-49 mg L(-1) was a rapid process providing complete conversion into ammonia in 1.5 h. Struvite precipitation conducted on enzyme hydrolysed urine sample proved to be an efficient process and ammonia removals up to 95% were obtained. Struvite precipitation also provided 50% organic nitrogen removal.     

Psychometric Evaluation of the T-CSUQ: The Turkish Version of the Computer System Usability Questionnaire

This article describes the development of a standardized computer system usability questionnaire for use with speakers of the Turkish language, the Turkish Computer System Usability Questionnaire, Short Version (T-CSUQ-SV). This new questionnaire, based on the English-language CSUQ, underwent careful translation and transformation through comprehensive psychometric evaluation. The results of the psychometric evaluation revealed an acceptable level of reliability, appropriate construct validity, and sensitivity to manipulation, indicating that Turkish usability practitioners should be able to use the T-CSUQ-SV with confidence when conducting user research.     

An overview of anonymity technology usage

Anonymity technologies enable Internet users to maintain a level of privacy that prevents the collection of identifying information such as the IP address. Understanding the deployment of anonymity technologies on the Internet is important to analyze the current and future trends. In this paper, we provide a tutorial survey and a measurement study to understand the anonymity technology usage on the Internet from multiple perspectives and platforms. First, we review currently utilized anonymity technologies and assess their usage levels. For this, we cover deployed contemporary anonymity technologies including proxy servers, remailers, JAP, I2P, and Tor with the geo-location of deployed servers. Among these systems, proxy servers, Tor and I2P are actively used, while remailers and JAP have minimal usage. Then, we analyze application-level protocol usage and anonymity technology usage with different applications. For this, we preform a measurement study by collecting data from a Tor exit node, a P2P client, a large campus network, a departmental email server, and publicly available data on spam sources to assess the utilization of anonymizer technologies from various perspectives. Our results confirm previous findings regarding application usage and server geo-location distribution where certain countries utilize anonymity networks significantly more than others. Moreover, our application analysis reveals that Tor and proxy servers are used more than other anonymity techniques.     

Fast transient analysis of incident field coupling to multiconductor transmission lines

Due to the rapid surge in operating frequencies and complexity of modern electronic designs, accurate/fast electromagnetic compatibility/interference analysis is becoming mandatory. This paper presents a closed-form SPICE macromodel for fast transient analysis of lossy multiconductor transmission lines in the presence of incident electromagnetic fields. In the proposed algorithm, the equivalent sources due to incident field coupling have been formulated so as to take an advantage of the recently developed delay extraction based passive transmission line macromodels. Also, a method to incorporate frequency-dependent per-unit-length parameters is presented. The time-domain macromodel is in the form of ordinary differential equations and can be easily included in SPICE like simulators for transient analysis. The proposed algorithm while guaranteeing the stability of the simulation by employing passive transmission line macromodel, provides significant speed-up for the incident field coupling analysis of multiconductor transmission line networks, especially with large delay and low losses.     

Mechanical Properties of Thermoplastic and Thermoset Composites Reinforced with 3D Biaxial Warp-knitted Fabrics

In this study, two types of thermoplastic matrices (low melting point polyethylene terephthalate (LPET) fiber and polypropylene (PP) fiber) and glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate the thermoplastic and thermoset composite materials with 3D biaxial warp-knitted fabrics. Thermoplastic and thermoset composites were fabricated using hot-press and resin transfer molding (RTM) methods. The fabricated samples were tested with tensile and three-point flexural tests. In thermoplastic composites, samples in the 90° direction and LPET matrix showed the best tensile and flexural properties with an improvement of 39 and 21% tensile modulus and strength, 16 and 8% flexural modulus and strength compared to the PP samples in the same direction. In thermoset composites, samples in the 90° direction and MWCNTs showed the best improvement of the flexural modulus and strength with 97 and 58% compared to the samples without MWCNTs. This improvement can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbon nanotubes.     

Circuit analysis of electromagnetic radiation and field couplingeffects for networks with embedded full-wave modules

With continually increasing operating frequencies, the analysis of electromagnetic interference (EMI)-related effects is becoming an important issue for high-speed designs. An algorithm is presented for fast analysis of radiation and incident field coupling effects in high-speed circuits. The proposed technique provides an efficient means for combining the solutions from full-wave field solvers such as the finite-difference time-domain (FDTD) method with circuit level simulators such as SPICE for calculating radiated/coupled fields in arbitrarily shaped interconnect structures. The technique speeds up the whole simulation process by employing a model-reduction-based approach, and also overcomes the numerical stability problems associated with the FDTD, in the presence of nonlinear terminations. In addition, the proposed algorithm provides a direct access to existing vast device libraries of SPICE in EMI analysis     

Methane OSR over Pt-Ni/δ-Al2O3: Performance and power law type kinetics

Methane oxidative steam reforming (OSR) performance of two bimetallic Pt-Ni/δ-Al₂O₃ catalysts, having Pt:Ni loadings, 0.2:10 and 0.3:10, were tested first. In the tests, residence time (W/F), carbon-to-oxygen (C/O₂) feed ratio, and temperature were used as the experimental parameters. Increase in temperature resulted in direct and indirect - through enhanced TOX yielding higher energy - increase in SR rate. As Pt:Ni metal loading ratio did not lead to significant changes in activity, the preliminary kinetic tests to determine merely kinetically controlled region were conducted over 0.2Pt-10Ni catalyst. Considering the outcomes of the preliminary tests, the kinetic experiments were performed for practical reaction conditions extending up to 20% methane conversion with feed ratio intervals of 4.0 < C/O₂ < 7.34 and 2.03 < S/C < 3.08 at two different residence time (W/F) values to obtain a power-law type rate equation. Reaction orders were estimated as 0.81, 1.60 and 0.44 for methane, oxygen and steam, respectively, by using multivariable non-linear optimization function of MATLAB?. The apparent activation energy of methane OSR was calculated as 24.61 kJ mol^?1 and pre-exponential factor as 0.110 μmol mgcat^?1 s^?1 kPa^?2.85 for the 375–450 °C temperature interval. The same analysis performed for a narrower temperature range, 375–425 °C, gave k₀ and E_A values as 0.251 μmol mgcat^?1 s^?1 kPa^?2.85 and 29.17 kJ mol^?1, respectively, confirming the high sensitivity of OSR pathway to temperature.     

Image Based and Hybrid Visual Servo Control of an Unmanned Aerial Vehicle

The use of unmanned aerial vehicles (UAVs) for military, scientific, and civilian sectors are increasing drastically in recent years. This study presents algorithms for the visual-servo control of an UAV, in which a quadrotor helicopter has been stabilized with visual information through the control loop. Unlike previous study that use pose estimation approach which is time consuming and subject to various errors, the visual-servo control is more reliable and fast. The method requires a camera on-board the vehicle, which is already available on various UAV systems. The UAV with a camera behaves like an eye-in-hand visual servoing system. In this study the controller was designed by using two different approaches; image based visual servo control method and hybrid visual servo control method. Various simulations are developed on Matlab, in which the quadrotor aerial vehicle has been visual-servo controlled. In order to show the effectiveness of the algorithms, experiments were performed on a model quadrotor UAV, which suggest successful performance.