RF Pogo-Pin Probe Card Design Aimed at Automated Millimeter-Wave Multi-Port Integrated-Circuit Testing

A prototype RF probe card is assembled to test the feasibility of Pogo-pins as robust probe tips for the automized testing of multiple-port millimeter-wave circuits. A custom-made ceramic housing machined from a low-loss dielectric holds an array of 157 Pogo-pins, each with 2.9 mm-length in fixed positions. The ceramic housing is then mounted onto a probe-card PCB for power-loss measurements on two signal-ground Pogo-pin connections arbitrarily selected from the array. The probing results on a test circuit with a simple thru-line indicate a successful power transfer with a small insertion loss of less than 0.5 dB per single Pogo-pin connection up to 25 GHz. A new probe card design using shorter Pogo-pins is being prepared to extend the operation frequency to beyond 40 GHz.

Oppnåelse av dybdelæring i et teknologiog design-prosjekt

The present case study examines a group of teacher students performing a Technology and Design project primarily intended for strengthening their competencies in electricity and electronics. The project was based on a traditional schema; a challenging task, design and problem-solving phases, decision making and finally assembling/building a real functioning product. The main purpose of the investigation was focusing on the type of competencies the students gained; transferable competence or rote learning, i.e. whether the project would facilitate deeper learning or not. The project was partly open-ended, where the students might conclude in different ways regarding their final circuit design. The motivating effect of having to alternate between calculations and circuit-testing, searching for faults, discussing with each other and finally succeeding, seemed to have a very positive effect on the overall learning outcome. At the end of the project the students had to solve a complete new circuit-construction challenge, with specifications differing from the ones in the original project, i.e. a new context. The demands for knowledge were similar to-, but higher than the first project, and they had to apply their newly acquired competency in a very different manner. All the student groups managed to solve the task in maximum 45 minutes. This tends to give evidence for deeper learning as an outcome of this particular project.

Sulfidizing Behavior of Complex Lead-Silver Ore: A Flotation Study

In this study, we investigate a low-grade oxidized lead ore containing noble metal silver, with complex mineralogy. The sulfurization behaviors of different types of lead-silver minerals at different pH values were analyzed using the chemical phase analysis method. The interactions between different types of lead-silver minerals and different types of collectors were investigated. An effective laboratory process was developed, and closed-circuit tests were carried out at industrial sites. We found that the order of difficulty for sulfidizing various lead minerals and silver minerals was (PbFe6(OH)12SO4)4 < PbCO3 < PbSO4 < Pb5(P/As/VO4)3Cl; Ag2AsS2 < AgCl < natural-Ag. Aerophine 3418A had the best selectivity and capture capacity of the silver minerals. In the laboratory, the total recovery of lead and silver was 65.16% and 87.81%, respectively. In industrial closed-circuit testing, flotation alone was used, which produced a total lead recovery yield of 67.71%, and a total silver recovery yield of 87.64%.

Tight Localizations of Feedback Sets

The classical NP–hard feedback arc set problem (FASP) and feedback vertex set problem (FVSP) ask for a minimum set of arcs ε ⊆ E or vertices ν ⊆ V whose removal G ∖ ε, G ∖ ν makes a given multi–digraph G =( V , E ) acyclic, respectively. Though both problems are known to be APX–hard, constant ratio approximations or proofs of inapproximability are unknown. We propose a new universal O (| V || E | 4 )–heuristic for the directed FASP. While a ratio of r ≈ 1.3606 is known to be a lower bound for the APX–hardness, at least by empirical validation we achieve an approximation of r ≤ 2. Most of the relevant applications, such as circuit testing , ask for solving the FASP on large sparse graphs, which can be done efficiently within tight error bounds with our approach.

Fault Coverage-Aware Metrics for Evaluating the Reliability Factor of Solar Tracking Systems

This paper presents a mathematical approach for determining the reliability of solar tracking systems based on three fault coverage-aware metrics which use system error data from hardware, software as well as in-circuit testing (ICT) techniques, to calculate a solar test factor (STF). Using Euler’s named constant, the solar reliability factor (SRF) is computed to define the robustness and availability of modern, high-performance solar tracking systems. The experimental cases which were run in the Mathcad software suite and the Python programming environment show that the fault coverage-aware metrics greatly change the test and reliability factor curve of solar tracking systems, achieving significantly reduced calculation steps and computation time.