ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of microdomain structures on the molecular orientation of poly(styrene-block-butadiene-block-styrene) triblock copolymerShinichi Sakurai, June Sakamoto, Mitsuhiro Shibayama, and Shunji NomuraCite this: Macromolecules 1993, 26, 13, 3351–3356Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://pubs.acs.org/doi/10.1021/ma00065a018https://doi.org/10.1021/ma00065a018research-articleACS PublicationsRequest reuse permissionsArticle Views391Altmetric-Citations64LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Orientation behavior of reciprocal lattice vectors of crystalites in orthogonal-biaxially stretched PVA film was investigated by means of pole figure analyses of X-ray diffraction. The orthogonal-biaxially stretching was performed under the following three fashions; simultaneous, strip biaxial, and two-step biaxial.1) For the simultaneous biaxial stretching, it was found that (101) plane tends to orient parallel to the film plane, but it randomly orients around the normal of film plane, and that (10_??_) plane becomes parallel to the normal of film plane.2) For the strip and two-stpe biaxial stretching, (101) plane tends to orient parallel to the film plane, but the behavior of (10_??_) plane changes with the deformation of orthogonal biaxial stretching.
Crosslinks by borate ions were introduced to improve mechanical properties of poly (ethylene-ran-vinyl alcohol) (EVOH), whose films have a very low oxygen permeability. Effects of crosslinks on the mechanical properties and oxygen permeability of the crosslinked films were studied by dynamic viscoelastic, differential scanning calorimetry, wide angle X-ray diffraction, and oxygen permeability measurements, in terms of their structural changes. The mechanical loss tangent due to the glass transition of EVOH at around 70°C was depressed and the decrease in the storage modulus above the transition temperature became less by introducing the borate crosslinks into EVOH. This indicates that the borate crosslinks are effectively formed in amorphous region and restrict the motion of amorphous chains. However, borate crosslinks prevent the crystallization of EVOH and the presence of NaOH, employed to ionize boric acid, leads to an increase in water regain in the film. Because of these effects, the oxygen barrier property became worse than that of non-treated EVOH films. Optimization of these properties is discussed by considering the preparation of gel films.
Abstract A deformation mechanism for polyethylene spherulites has been proposed which is based on the affine transformation method. Individual crystal lamellae are taken as the orientation units within the spherulites and are allowed to rotate around the a ‐ and b ‐ axes of the crystal. Deductions based on this model and on previous models are compared with experimental results obtained with four kinds of polyethylene film. These results agree fairly well with the predictions of the present model and suggest that the plastic deformation of crystal lamellae by gliding along the (110) plane predominates over the untwisting of crystal lamellae at the initial stage of deformation.
In order to use a coil wound with REBCO-coated conductor in a conduction cooling configuration, ac loss of the coil should be quantitatively predicted and designed under the operating conditions, for example during charging-up and -down, or shutdown operation. A tape-shaped REBCO-coated conductor is suited to be composed of a stack of single pancake coils for generating high magnetic field. Various researchers have measured and evaluated the ac loss of REBCO tape; however, there are few reports about the ac loss of the coil as measured at liquid nitrogen temperature. In this report, the ac loss of REBCO coil composed of a stack of 22 single pancakes with 50 mm in inner diameter, 132 mm in outer diameter, and 105 mm in height, generating 13.5T at 10 K, was measured by electrical method and evaluated with conduction cooling configuration. The experimental results were compared with the calculated results and discussed.
A 3 T HTS MRI model magnet equipped with conductive epoxy resin for quench protection was designed and fabricated in 2021 and the REBCO multicoil generated 3 T with 143 A stably with no abnormal voltages. In this coil, the electrically conductive epoxy resin is attached to the edge of the winding as a bypass circuit between turns so that the excessive current can flow across turns in the radial direction to suppress local heat generation automatically. However, when the voltage of the coil rises as a start point in a quench protection process, the DC power supply is shut down by a quench detector and the magnet is suddenly discharged. Then, part of the magnetic stored energy is consumed in the coil and the coil temperature increases, which suggests the load factor increases during the sudden discharging operation. In this study, the sudden discharging tests were performed, and the behavior of the coil voltages and temperatures was evaluated at 30 K and 40 K using the middle-scale REBCO coil that had large inductance and high stored energy (3 T, 91 H, 1 MJ). After that, the overcurrent tests were performed for the verification of the quench protection at 50 K. The coil temperature reached 72 K at maximum, however, thermal runaway was avoided and the REBCO coil was protected.
Since FY 2004, a four-year Japanese national project has been ongoing to develop an HTS-SMES as a sub-program of the Development of Superconducting Power Network Control Technology. The purpose of this project is to confirm the performance of a high energy density SMES coil with Bi-2212 cables. This coil system is composed of an NbTi outer coil and a Bi-2212 inner coil, consisting of 16 double pancakes. A Bi2212 cable of 140 m length is used for the double-pancake windings, and reinforcing materials are co-wound with the cable. A winding inner diameter of 360 mm was set according to the bending tolerance of the cable. The magnet is to be cooled at 4.2 K by liquid helium in order to obtain high overall current density. In the first year of this project, a conceptual design and various experiments for HTS magnet were carried out. This paper describes the test results of the HTS experimental coil that was developed to evaluate the electrical and thermal characteristics of an HTS. It is important to minimize deterioration and damage to the cable, because such defects cause fatal impact to the coil. Consequentially, high accuracy measurement of V-I characteristics up to10−8 V/cm range was performed in this experiment.
A superconducting magnet for a 40 T hybrid magnet was designed to be as compact as possible, and to be constructed with epoxy-impregnated layer winding using highly strengthened Nb/sub 3/Sn wires. The magnet generates 16 T in a 420 mm inner diameter of windings. The total coil mass of 4.1 tons, approximately 40% of the conventional cryostabilized magnet wound with copper-matrix wire was attained.
Ordering process of lamellar microdomains of poly(styrene‐block‐butadiene‐block‐styrene) (SBS) triblock copolymers in melts has been studied using small‐angle X‐ray scattering (SAXS). The SAXS profiles were analyzed by means of the theoretical calculation based on the one‐dimensional paracrystal model so as to characterize quantitatively how the lamellae which were formed through coalescence of cylindrical microdomains ordered. As a result of the analysis, it was found that the distribution of the interlamellar distance and the thickness distributions of polystyre (PS) and polybutadiene (PB) lamellae decreased, whereas the interlamellar distance and the interfacial thickness did not definitely change with time.
A conduction-cooled REBCO racetrack coil that is stored and impregnated in a stainless steel case is proposed for mechanical reinforcement of the straight parts. Two racetrack coils composed of a stack of four single pancakes wound with two kinds of the REBCO tapes were fabricated and tested using conventional and new advanced conduction cooling systems, respectively. As the latter a more simplified cooling structure for a REBCO coil without the need for a conventional thermal radiation shield is currently under development. One challenge is restricting the flow of heat to the coil when the cryocooler stops due to an unexpected electrical and/or mechanical breakdown. In this research, the stainless steel case was thermally connected to a single-stage GM cryocooler. Most of the heat load was received by the case, and thermal resistance layers were inserted between the case and the coil surface for controlling the flow of heat into the coil. The REBCO coil was cooled indirectly and operated successfully without any degradation and the temperature rise when the cryocooler stopped was evaluated by experiments and calculations.
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