‘Getting stuck’ in analogue electronics: Threshold concepts as an explanatory model

Could the challenge of mastering threshold concepts be a potential factor that influences a student's decision to continue in electronics engineering? This was the question that led to a collaborative research project between educational researchers and the Faculty of Engineering in a New Zealand university. This paper deals exclusively with the qualitative data from this project, which was designed to investigate the high attrition rate of students taking introductory electronics in a New Zealand university. The affordances of the various teaching opportunities and the barriers that students perceived are examined in the light of recent international research in the area of threshold concepts and transformational learning. Suggestions are made to help students move forward in their thinking, without compromising the need for maintaining the element of intellectual uncertainty that is crucial for tertiary teaching. The issue of the timing of assessments as a measure of conceptual development or the crossing of thresholds is raised

Epitaxial designs for maximizing efficiency in resonant tunnelling diode based terahertz emitters

We discuss the modelling of high current density InGaAs/AlAs/InP resonant tunneling diodes to maximize their efficiency as THz emitters. A figure of merit which contributes to the wall plug efficiency, the intrinsic resonator efficiency, is used for the development of epitaxial designs. With the contribution of key parameters identified, we analyze the limitations of accumulated stress to assess the manufacturability of such designs. Optimal epitaxial designs are revealed, utilizing thin barriers, with a wide and shallow quantum well that satisfies the strained layer epitaxy constraint. We then assess the advantages to epitaxial perfection and electrical characteristics provided by devices with a narrow InAs sub-well inside a lattice-matched InGaAs alloy. These new structures will assist in the realization of the next-generation submillimeter emitters

High-Tc ramp-type Josephson junctions on MgO substrates for Terahertz applications

The authors successfully fabricated high-Tc ramp-type junctions with PrBa2Cu3-xGaxO7-δ (PBCGO: x=0.1, 0.4) barriers on MgO substrates. The junctions showed resistively shunted Josephson junction (RSJ)-like I-V curves with thermally and voltage activated conductivity. The IcRn products for these junctions scaled very well with the Ga-doping. Maximum response of the junctions for 100-GHz millimeter-wave irradiation could be observed up to 12 mV corresponding to 6 THz. Using far infrared laser radiation, we confirmed a terahertz (THz) response of these junctions. These results show promise for THz-wave applications of ramp-type Josephson junctions

"The European Community and Japan: Bi(tri)lateral Trade in World Context"

This paper first examines the institutional context of EC trade policy and assesses the real level of protection that policy has afforded. It then examines the question of how "common" the policy has in fact been and how it has related to competition policy, devoting a special section to the Common Agricultural Policy (CAP). The next two sections discuss crucial issues in the trilateral relationship between the EC, Japan, and the US by focusing on the manufacturing sectors of electronics and cars. In shifting the perspective towards the future this paper focuses first on the concept of "strategic trade policy" and then at the special issues raised by the reform process that "1992 has brought, if it has, in Eastern Europe. The paper ends by posing two fundamental and interrelated questions. Has "1992" brought the European Community closer to the rest of the world? And what is the future position of Europe in the international division of labor

Pending U.S. and EU Free Trade Agreements with South Korea: Possible Implications for Automobile and Other Manufacturing Industries

[Excerpt] South Korea has negotiated free trade agreements (FTAs) with the United States and the European Union (EU), but neither agreement has yet been approved. The U.S. Congress must approve the United States and South Korea free trade agreement (KORUS FTA) and the European Parliament must vote on the European Union and South Korea free trade agreement (KOREU FTA) before the FTAs can take effect. If the FTAs are ratified, it is possible there could be a “first mover” advantage for either the United States or the European Union, depending on which FTA is approved first. Some argue that both agreements have shortcomings and should not be approved. This report provides U.S. lawmakers with a comparison of the manufacturing components in the KORUS and KOREU FTAs. Congressional interest in an FTA between the European Union and South Korea mostly centers on those U.S. industries competing with European industrial sectors, especially motor vehicles. The two pending FTAs raise questions about what it could mean for U.S. manufacturers if the United States takes longer, or fails altogether, to implement the KORUS FTA, while the European Union and South Korea possibly move ahead to approve and implement their outstanding FTA. In such a case, the possibility exists that the removal of tariff and nontariff barriers between the European Union and South Korean markets could result in U.S. manufacturers losing South Korean market share to European competitors. On balance, most U.S. and European manufacturing sectors, with some auto manufacturers in particular among notable dissenters, argue that the pending FTAs will be beneficial and are largely supportive. On the other side, labor unions in the United States and the European Union are considerably more skeptical, claiming that South Korean companies could be the biggest beneficiaries, since they could gain even greater access to the significantly larger U.S. and EU markets. Labor union leaders say the FTA will result in further job losses as their respective manufacturing workforces compete for market share with competitive South Korean manufacturers in their own domestic markets

Difference of Oxide Hetero-Structure Junctions with Semiconductor Electronic Devices

Charge carrier injection performed in Pr0.7Ca0.3MnO3 (PCMO) hetero-structure junctions exhibits stable without electric fields and dramatic changes in both resistances and interface barriers, which are entirely different from behaviors of semiconductor devices. Disappearance and reversion of interface barriers suggest that the adjustable resistance switching of such hetero-structure oxide devices should associate with motion of charge carriers across interfaces. The results suggested that injected carriers should be still staying in devices and resulted in changes in properties, which guided to a carrier self-trapping and releasing picture in strongly correlated electronic framework. Observations in PCMO and oxygen deficient CeO2 devices show that oxides as functional materials could be used in microelectronics with some novel properties, in which interface is very important.Comment: 8 pages, 4 figure

Mobility enhancement and highly efficient gating of monolayer MoS2 transistors with Polymer Electrolyte

We report electrical characterization of monolayer molybdenum disulfide (MoS2) devices using a thin layer of polymer electrolyte consisting of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO4) as both a contact-barrier reducer and channel mobility booster. We find that bare MoS2 devices (without polymer electrolyte) fabricated on Si/SiO2 have low channel mobility and large contact resistance, both of which severely limit the field-effect mobility of the devices. A thin layer of PEO/ LiClO4 deposited on top of the devices not only substantially reduces the contact resistance but also boost the channel mobility, leading up to three-orders-of-magnitude enhancement of the field-effect mobility of the device. When the polymer electrolyte is used as a gate medium, the MoS2 field-effect transistors exhibit excellent device characteristics such as a near ideal subthreshold swing and an on/off ratio of 106 as a result of the strong gate-channel coupling.Comment: 17 pages, 4 figures, accepted by J. Phys.