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This paper reports on experimental studies of point discharge in oil-paper insulation under different hydraulic pressures. The point partial discharge of oil-paper insulation under different hydraulic pressure was measured for the first time. With the help of a commercial partial discharge detector, five discharge parameters under constant AC voltage were recorded and plotted as curves. These show that the partial discharge under very low pressure developed very quickly after it was initiated. So, care should be taken with oil-paper equipment operating at high altitudes, because once the discharge is initiated, it would develop into a catastrophe in a relatively short time. The partial discharge inception voltage and breakdown voltage increased with pressure, but the rising rates decreased with the increase of pressure. The discharge parameters decreased with pressure but the difference between the adjacent curves became smaller and smaller, which is called the saturation characteristic of the hydraulic pressure’s effect on discharge. Therefore, very high hydraulic pressure is not necessary for weakening the partial discharge in oil paper insulation. It is believed that the hydraulic pressure influences the discharge in the oil-paper insulation by changing the state of the gas in this compound insulation system. This paper provides a reference for the operation and maintenance of oil-paper insulation equipment running in high-altitude areas. Adjusting hydraulic pressure might be an effective and economical way to reduce the size and weight of oil-paper insulation equipment.

A square spiral incision was introduced into a 15 × 15 cm regular quadrilateral conductive film to study the modulation of electrothermal distribution by kirigami structure. Based on the simulation of finite element method, the transition from thermal focusing to thermal defocusing could be achieved by increasing the length of connection between adjacent modules. The effective electrothermal area can be increased by nearly two times through increasing the length increment of the notch length between adjacent modules. The maximum temperature was decreased from 254 °C to 44 °C, and the temperature difference was adjusted from 76 °C to 4 °C by increasing the number of kirigami module. Through the contact temperature measurement experiment on graphite paper kirigami structure, the trends could be verified. By creating an equivalent circuit model and considering the influence of heat conduction, the peak temperature at the center of the structure and the decrease of the overall temperature could be explained. By deriving the relationship between the temperature of conductive film of kirigami structure with time and position, the electrothermal characteristics of previously reported graphene kirigami structure could be predicted.

Surface-enhanced Raman spectroscopy (SERS) is a unique technique that allows us to detect samples in trace quantities. The spectral intensities of the characteristic Raman peaks of the analyte molecule are enhanced manifold in the presence of noble metal nanoparticles (NPs). The existence of NPs is necessary to couple the incident electromagnetic field with NPs through the localized surface plasmon resonance phenomenon, which primarily contributes to the enhancement of an SERS signal. The present work demonstrates the working of a paper-based SERS substrate to detect and quantify two pharmaceutical drugs—paracetamol and aspirin—in water. The proposed SERS substrate was obtained by drop-casting silver NPs over printing grade 100 grams per square meter (GSM) paper. 100 GSM denotes the class of paper where 100 grams of raw materials (cellulose) is used per square meter to manufacture the paper. The performance of the designed SERS substrate was initially evaluated with two Raman active samples—malachite green and rhodamine-6G. The applicability of the proposed SERS substrate was evaluated further through monitoring the Raman spectra of the two aforementioned pharmaceutical drugs in different field-collected water samples, thus establishing the reliability of the scheme in a real field environment.

Femtosecond laser ablation of freestanding reduced graphene oxide (rGO) paper and its mechanisms were investigated. An abnormal phenomenon was discovered: the ablated area remained unchanged for the rGO paper with an increasing number of pulses, which was found to be a general feature for a large range of laser fluences. We also studied femtosecond laser ablation of graphene oxide paper and highly oriented pyrolytic graphite film for comparison. Experimental results indicated that the abnormal phenomenon was unique to the rGO paper. As revealed by a combination of SEM, TEM, XRD and Raman techniques, femtosecond laser nonthermal ablation through rolling up of rGO nanoflakes, induced by the distinctive multi-level layer-by-layer structures and the ultrafast energy relaxation of the rGO paper, were considered to be responsible for the non-incubation effect.

Finding a low cost substrate for surface-enhanced Raman spectroscopy (SERS) yielding enhanced, reproducible Raman signal from Raman active samples has been a longstanding goal for researchers for years. Herein, we demonstrate the fabrication of such a SERS substrate from paper. The proposed paper-based SERS substrate was developed by attaching polyvinylpyrrolidone (PVP) capped silver nano-particles (AgNPs) to printing grade paper. The performance of the substrate has been evaluated for paper substrates of various grades (in grams per square meter; GSM). The usability of the developed substrate for detection of two Raman active samples—namely, malachite green (MG) and rhodamine6G (R6G)—is reported. In addition to these samples, the reproducibility of the designed substrate has been evaluated for 1,2-bis(4-pyridyl)ethylene (BPE); a good degree of reproducibility was observed. Finally, applicability of the proposed substrate for reliable detection of Raman signals from two more important samples—namely, glucose and urine—has been successfully demonstrated.

Multi-walled carbon nanotubes (MWNT) and polyaniline are coated on an electro-active paper (EAPap) to improve the performance of the bending actuator, and its performance is tested. EAPap actuators made with cellulose paper have merits in terms of large bending displacement, ultra-lightweight, dryness, low actuation voltage and power consumption, low cost and biodegradability. However, the force output of actuators is small and the actuation frequency is low. Thus, MWNT and emeraldine salt polyaniline (PANI) are coated on the EAPap material to improve the force and the actuation frequency. The MWNT and PANI solution is made by sonication, and the sonication time and the weight per cents of the MWNT and PANI are optimized to improve the hybrid actuator performance. The optimum condition is associated with conversion of the partial conductive state PANI into the emeraldine formed PANI by the chemical bonding between the MWNT and PANI. The performance improvement of the EAPap actuator coated with MWNT/PANI is investigated in terms of displacement, blocking force and efficiency. In the presence of an electric field (0.35 V µm−1) on the hybrid EAPap actuator, 250% of the output force, 160% of the resonance frequency and 50% of efficiency are improved.

Some elements of the study of fibrous structure are presented in this paper. X-ray synchrotron microtomography is used to provide information about the three-dimensional structure. In this context a segmentation method is proposed to separate the different components of the porous material considered (paper).

For conventional thin-film transistors (TFTs), bottom-gate or top-gate configuration is always adopted because the channel current is generally controlled by vertical capacitive coupling. In this article, depending on huge lateral electric-double-layer (EDL) capacitor induced by spatial movement of protons in phosphosilicate glass (PSG) solid electrolyte dielectrics, coplanar-gate indium-zinc-oxide (IZO)-TFTs based on the lateral capacitive coupling were fabricated on bare paper substrates. The PSG solid electrolyte films here were used at the same time as gate dielectrics and smooth buffer layers. These TFTs showed a low-voltage operation of only 1 V with a large field-effect mobility of 13.4 cm(2) V-1.s, a high current on/off ratio of 6 x 10(6) and a small subthreshold swing of 75 mV/decade. Furthermore, with introducing another coplanar gate, AND logic operation was also demonstrated on the coplanar dual-gate TFTs. These simple lateral-coupling coplanar-gate IZO-TFTs on bare paper substrates are very promising for low-cost portable sensors and bio-electronics.

We have studied the dynamics of two-phase flow in highly compressible porous media. As an application, we consider a (1 + 1)-dimensional 'transverse' flow model of water removal in a paper machine press section. Within the model, the system of water, air and the fibrous solid network is perceived as a homogeneous mixture of three interacting fluids under an external, time-dependent load. The flow of the three components is governed by the continuity equations and the generalized Darcy's laws. The rate of strain of the solid matrix is determined using a phenomenological stress-strain relationship which can include hysteresis and permanent deformation. The effective stress also includes the drag applied to the solid matrix by flowing water and air. The interactions (drag forces) between the three components are determined from either experimental effective permeabilities or interaction terms derived from a simple 'annular plug' capillary flow model.

With the great demand in the applications of flexible electronics, the methods leading to improvements in the electrical and mechanical performance have been widely investigated. In this work, we firstly prepared a hybrid composite ink using Ag nanoparticles and graphene. Then, a hot-press sintering process was deployed to obtain the desired electrical tracks which could be applied in flexible electronics. We have systematically investigated the effects of sintering time, pressure and temperature, as well as the different percentage of weight (wt%) of graphene for the electrical and mechanical performance of sintered electrical tracks. We achieved reasonably low electrical resistivity at low sintering temperature (120 °C). Specifically, the resistivity reaches 6.19 × 10−8 Ω m which is just 3.87 times higher than the value of bulk silver. Additionally, the prepared hybrid composite ink obtained better electrical reliability against bending test comparing with Ag nanoparticle ink. Finally, the optimal wt% of graphene and potential effect to the electrical and mechanical performance were also investigated.

The 19th International Colloquium on Magnetic Films and Surfaces (ICMFS 2006) was held on 14–18 August 2006 at the Sendai International Center in Sendai, Japan. The purpose of the Colloquium was to bring together scientists working on magnetic thin films and surfaces and to provide an opportunity for presentation and discussion of recent experimental and theoretical advances in the field. 285 scientists from 17 countries (Japan: 167, overseas: 118) participated in the Colloquium, as well as 6 family members. There were 56 oral and 178 poster presentations. The oral presentations consisted of 3 plenary talks, 23 invited talks and 30 contributed talks. The number of presentations by scientific category are as follows: Spin dependent transport: 43 Magnetic storage/memory: 9 Magnetization reversal and fast dynamics: 15 Spin injection and spin transfer torque: 26 Magnetic thin films and multilayers: 71 High spin polarization materials: 17 Hard and soft magnetic materials: 3 Magneto-optics: 5 Characterization techniques for thin films and surfaces: 7 Exchange coupling: 13 Micro- and nanopatterned magnetic structures: 18 Micromagnetic modelling: 2 One of the characteristics of the present Colloquium is an increase in the number of presentations in the field of spin-electronics, as seen above. This Cluster Issue of Journal of Physics D: Applied Physics includes several important papers in this rapidly developing field. We believe that, in the future, the field of magnetic materials will maintain its popularity and, on top of that, other fields such as spintronics materials, materials related to life sciences and medicine and also materials related to the environment will be investigated further. The ICMFS Conference started in London in 1964, and is now one of the world-wide conferences on magnetism. The Colloquium has been held in Japan four times now: the previous ones being the 5th ICMFS in the Mount Fuji area, the 10th at Yokohama and the 17th at Kyoto, which was organized by Professors Shinjo and Maekawa. The city of Sendai, where the 19th ICMFS was held, is the historical place for magnetism research in Japan. Kotaro Honda, who was a professor of Tohoku University in Sendai, laid the foundation for this research in Japan, and he was followed by Siji Kaya, Haraku Masumoto and Minoru Takahashi, also professors of Tohoku University. They continued the spirit founded by Honda and contributed greatly to the progress of research in magnetism. Therefore, it was a great pleasure for the organizers to have the ICMFS Conference come to Sendai. The 19th ICMFS Colloquium was co-hosted by the Japanese Society for the Promotion of Science and the Foundation Advanced Technology Institute and supported by the Japanese Society of Applied Physics, the Magnetics Society of Japan, the Physical Society of Japan and the Japan Institute of Metals. This colloquium was also jointly held with the Conference on the Physics and Application of Spin-related Phenomena in Semiconductors (PASPS). All the members of the Organizing Committee would like to thank the members of the International Advisory Committee for scientific and administrative advice, and the Sendai Tourism and Convention Bureau, the Iwatani Naoji Foundation, the Asahi Glass Foundation and the Intelligent Cosmos Academic Foundation for their financial support. Without doubt, the Colloquium was a great success overall. The smooth and excellent running of the Colloquium would not have been possible without the assistance of the Program Committee and local members of the Colloquium.

A coated paper surface is assumed to be random and isotropic. The height of rough paper is considered to be a two-dimensional random variable and is represented in terms of the spectral moments. These moments are used to characterise the paper surface for print quality. The percentage void and the sharpness index are derived in addition to the statistics of surface such as density of summits, contour length, excursion area, etc. in order to have better understanding of the behaviour of paper under printing. The analysis of eight sets of data collected on light and heavy coating weight (50-75 g m-2) paper samples revealed that the proposed method is capable of characterising the paper surfaces of different textures in a quantitative way. The ranking results of the proposed parameters are also found to be in close agreement with the results of other methods such as electron micrographs and MAN test.

This cluster issue of Journal of Physics D: Applied Physics contains a collection of papers based on invited talks given at the 2nd International Symposium on Advanced Magnetic Materials and Applications 2010 (ISAMMA 2010) held from 12–16 July 2010 in Sendai, Japan. ISAMMA is the first consolidated symposium of three independent symposia held in the Asian region. ISPMM (International Symposium on Physics of Magnetic Materials) of Japan started in 1987 in Sendai, and was held six times: Beijing (1992), Seoul (1995), Sendai (1998), Taipei (2001) and Singapore (2005). ISAMT (International Symposium of Advanced Magnetic Technology) of Taiwan and SOMMA (International Symposium on Magnetic Materials and Applications) of Korea both began in 1999 and were each held five times up to 2005. ISAMMA was established as a new international symposium which will be held every three years in Asia. The concept of this unified international symposium was mainly led by Professor M Takahashi, Conference Chair of ISAMMA 2010. The first memorial symposium, ISAMMA 2007, was held in Jeju Island, Korea, during the period from 28 May to 1 June 2007. The main purpose and scope of ISAMMA is to provide an opportunity for scientists and engineers from all over the world to meet in Asia to discuss recent advances in the study of magnetic materials and their physics, spin-related phenomena and materials. The categories of ISAMMA 2010 were: fundamental properties of magnetic materials; hard/soft magnetic materials and applications; spintronics materials and devices; structured materials; multi functional magnetic materials; spin dynamics and micromagnetics; magnetic storage; materials for applications (sensors, high-frequency, power, and bio/medical devices); magnetic imaging and characterization. The scientific programme began on Tuesday 13 July 2010 with the opening remark by the Symposium Chairman. The conference was attended by 511 participants from 23 countries, with about 40 per cent from overseas. The programme involved 4 plenary talks, 37 invited talks, 85 contributed talks and 352 posters. All submitted papers were reviewed in order to meet the standards of Journal of Physics D: Applied Physics and Journal of Physics: Conference Series. We are grateful to all participants for their valuable contributions and active discussions. We gratefully acknowledge the financial support of 17 Japanese companies and 7 Japanese foundations. Invited papers from ISAMMA 2010 Contents Current status and recent topics of rare-earth permanent magnets S Sugimoto Alloying effect on the magnetic properties of RFeB-type bulk magnets H W Chang, C C Hsieh, J Y Gan, Y T Cheng, M F Shih and W C Chang Coercivity distributions in Nd–Fe–B sintered magnets produced by the grain boundary diffusion process H Nakamura, K Hirota, T Ohashi and T Minowa Recent progress in high Bs Fe-based nanocrystalline soft magnetic alloys M Ohta and Y Yoshizawa Electric-field effects on magnetic anisotropy in Pd/Fe/Pd(0 0 1) surface Shinya Haraguchi, Masahito Tsujikawa, Junpei Gotou and Tatsuki Oda Gate modulation of spin precession in a semiconductor channel Hyun Cheol Koo, Jae Hyun Kwon, Jonghwa Eom, Joonyeon Chang, Suk Hee Han and Mark Johnson Ferromagnetic resonance of epitaxial Fe nanodots grown on MgO measured using coplanar waveguides M Mizuguchi and K Takanashi Switching phase diagrams of current-induced magnetization switching in asymmetric MgO-based magnetic tunnel junctions Seung-Young Park, Jae-Ho Han, Se-Chung Oh, Jang-Eun Lee, Kyung-Tae Nam, Hyun-Woo Lee, Younghun Jo and Kyung-Jin Lee Temperature dependence of spin-dependent transport properties of Co2MnSi-based current-perpendicular-to-plane magnetoresistive devices Y Sakuraba, K Izumi, S Bosu, K Saito and K Takanashi Adsorbate-induced spin-polarization enhancement of Fe3O4(0 0 1) A Pratt, M Kurahashi, X Sun and Y Yamauchi Antiferromagnetic coupling between spinel ferrite and α-Fe layers in Fe3–δO4/MgO/Fe(0 0 1) epitaxial films Hideto Yanagihara, Yuta Toyoda and Eiji Kita Monte Carlo simulations of the magnetocaloric effect in magnetic Ni–Mn–X (X = Ga, In) Heusler alloys V D Buchelnikov, V V Sokolovskiy, S V Taskaev, V V Khovaylo, A A Aliev, L N Khanov, A B Batdalov, P Entel, H Miki and T Takagi Changes in electronic states and magnetic free energy in La1−z Ce z (Fe x Si1−x )13 magnetic refrigerants A Fujita, S Fujieda and K Fukamichi Garnet composite films with Au particles fabricated by repetitive formation for enhancement of Faraday effect H Uchida, Y Mizutani, Y Nakai, A A Fedyanin and M Inoue Control of magnetic domain wall displacement using spin current in small in-plane magnetic field in Permalloy nanowires Yoshihiko Togawa, Takashi Kimura, Ken Harada, Akira Tonomura and Yoshichika Otani Magnetic-field tunable transmittance in a ferrofluid-filled silicon nitride photonic crystal slab H M Lee, L Horng and J C Wu Evaluation of a miniature magnetostrictive actuator using Galfenol under tensile stress Toshiyuki Ueno, Hidemitsu Miura and Sotoshi Yamada Sub-nm resolution depth profiling of the magnetic structure of thin films by the depth-resolved x-ray magnetic circular dichroism technique K Amemiya and M Sakamaki

This paper reports that nanocoating of polypyrrole (PPy) and ionic liquid (IL) on cellulose film improves the electromechanical performance and durability of a cellulose electro-active paper actuator. Cellulose–PPy–IL nanocomposites were fabricated by the polymerization-induced adsorption process of PPy followed by subsequent activation in IL solutions. X-ray photoelectron spectroscopy, transmission electron microscopy and secondary ion mass spectroscopy analyses validated the successful nanocoating of the PPy and IL layers on the cellulose. The results revealed that the cellulose–PPy–IL nanocomposites are suitable for durable bending actuators working under ambient conditions. Preparation, characterization and performance test of the nanocomposites are explained.