Modifying the thermal and mechanical properties of poly(lactic acid) by adding lithium trifluoromethanesulfonate

The effect of the addition of lithium trifluoromethanesulfonate (LiCF₃SO₃) on the linear viscoelastic properties, crystallization behavior, and mechanical properties of poly(lactic acid) (PLA) was studied. The glass transition temperature (T_g) was enhanced by adding LiCF₃SO₃, without any loss of transparency of the PLA. This was attributed to the ion-dipole interaction between the lithium cation and oxygen atom in the PLA carbonyl group. The interaction weakened at higher temperature. Consequently, the rheological terminal region was clearly detected, which suggested that the system possessed good melt-processability. The Young’s modulus and yield stress at room temperature were also enhanced by the addition of LiCF₃SO₃, although the toughness was reduced due to the brittle failure. Finally, the presence of LiCF₃SO₃ retarded the crystallization of PLA, because the segmental motion of the PLA chains was reduced.     

Photo-induced deformation behavior depending on the glass transition temperature on the surface of urethane copolymers containing a push-pull type azobenzene moiety

Urethane copolymers containing a push-pull type azobenzene moiety with the same dye content were synthesized to investigate the relationship between photo-induced deformation and molecular mobility. The copolymers exhibit different glass transition temperatures (T_g), from 46 to 143 °C, due to their different main chain structures. An indented nanostructure induced by the optical near field around the polystyrene microspheres and a surface relief grating (SRG) induced by exposure to a two-beam interference pattern were examined using films of copolymers. We found the dependency of the deformation efficiency on T_g was inverted depending on the irradiation power. The deformation depth increased with T_g under high power irradiation in both the indented nanostructure and the SRG forming experiments. In contrast, the deformation depth of the SRG decreased with increasing T_g under low power irradiation. The discovery of this inverted tendency suggests that, in addition to the molecular mobility, we should consider other factors in the deformation mechanism, such as the recovery of deformation, the degree of plasticization, and the thermal effects.     

Optimum control scheme for the maximum efficiency drive of linear synchronous motor used for ropeless elevator

Our research group at Musashi Institute of Technology is currently concentrating on the improvement of the overall efficiency for driving ropeless elevators using a linear synchronous motor (LSM). Since these elevators are ropeless, counterweights cannot be installed in the system. Therefore, the linear motors must develop a higher thrust force. In addition to the improvement of the efficiency of LSM it is also necessary to develop a high‐efficiency drive control method. Our laboratory is involved in studies on efficiency improvement. In order to design an efficient control system, we believe it is necessary to understand changes of efficiency caused by variations of driving conditions, such as load mass, velocity, and required thrust force. The dynamic control method changing the operating point to achieve the maximum power is known as maximum power point tracking (MPPT). This approach is useful and can be applied to the control of LSM for ropeless elevators. The car cage of a ropeless elevator periodically repeats acceleration and deceleration cycles in the process of ascent and descent motions. The optimum‐minimum‐energy consumption is obtained if the system is always operated at the maximum efficiency, even if the drive conditions change. In this paper, we first discuss the basic characteristics of LSM for ropeless elevators. Then, based on these characteristics, we derive the maximum efficiency loci as a unique combination of a current and a power angle for a specific condition. We also provide a design of the MPPT controller of LSM and analyze results of simulation of driving the LSM using MPPT. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 70–78, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20061     

A study of the flywheel capacity of the power compensator for the wind turbine generator

Nowadays, the Wind Turbine Generator (WTG) system is remarkably increasing as a renewable energy resource in Japan. But in the WTG, the power fluctuations caused by the wind speed fluctuation are the most crucial issue in providing their energy to the utility. It was found that a power compensation system (PCS) of suitable capacity is not yet available. In this paper, the time range and standardized wind speed including fluctuations are discussed. We estimated the storage capacity of PCS at different wind profiles by standardization of wind speed and verified the validity of their capacities using a computer simulation. In this way we determined the suitable capacity of the power compensation system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(4): 64–71, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10122     

Purification and partial amino acid sequences of the binding protein from Bombyx mori for CryIAa delta-endotoxin of Bacillus thuringiensis

The binding protein for Bacillus thuringiensis delta-endotoxin, CryIAa, from the brush border membrane of the midgut of Bombyx mori was purified by the dot blot method and delta-endotoxin affinity chromatography. The binding protein was purified to 235-fold enrichment from cholic acid extracts of brush border membranes from B. mori midgut by activated CryIAa-affinity chromatography and DEAE ion-exchange chromatography. The purified binding protein showed a single band of 180 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis and this band specifically reacted to 125I-labeled CryIAa on Immobilon membrane. The affinity of the binding protein for CryIAa was equivalent to that of the brush border membrane vesicles and solubilized membrane proteins. Partial amino acid sequences of the binding protein showed sequence similarity to the cadherin-like binding protein for CryIAb from Manduca sexta, but not for CryIAc binding protein from M. sexta and Heliothis virescens.     

Hyperexpression of the gene for a Bacillus alpha-amylase in Bacillus subtilis cells: enzymatic properties and crystallization of the recombinant enzyme

We have constructed a new excretion vector, pHSP64, to develop a hyperexcretion system for Bacillus subtilis [Sumitomo et al., Biosci. Biotech. Biochem., 59, 2172-2175 (1995)]. The structural gene for a novel liquefying semi-alkaline alpha-amylase from the alkaliphilic Bacillus sp. KSM-1378 was amplified by PCR. It was cloned into a SalI-SmaI site of pHSP64 and the recombinant plasmid obtained was introduced into B. subtilis. The transformed B. subtilis hyperproduced the alpha-amylase activity extracellularly, corresponding to approximately 1.0 g (5 x 10(6) units) per liter of an optimized liquid culture. The recombinant enzyme was purified to homogeneity by a simple purification procedure with very high yield. No significant differences in physiochemical and catalytic properties were observed between the recombinant enzyme and the native enzyme produced by Bacillus sp. KSM-1378. The enzymatic properties of the recombinant enzyme were further examined with respect to the responses to various metal ions. The recombinant enzyme could easily be crystallized at room temperature within one day in a buffered solution of 10% (w/v) ammonium sulfate (pH 6.5).     

OCDMA over WDM PON-solution path to gigabit-symmetric FTTH

It will be revealed that a myth of deploying low bit-rate uplink fiber-to-the-home (FTTH) services while providing a high bit-rate downlink is wrong. Therefore, for the future broadband FTTH services, the focus should be on the capability to provide gigabit- or even multigigabits-per-second both in up- and downlinks, namely gigabit symmetric systems. Optical code-division multiple access (OCDMA) now deserves a revisit as a powerful alternative to time-division multiple access and wavelength-division multiple (WDM) access in FTTH systems. In this paper, the authors will first highlight the OCDMA systems. The system architecture and its operation principle, code design, optical en/decoding, using a long superstructured fiber Bragg grating (SSFBG) en/decoder, and its system performance will be described. Next, an OCDMA over WDM passive optical network (PON) as a solution for the gigabit-symmetric FTTH systems will be proposed. The system architecture and the WDM interchannel crosstalk will be studied. It will be shown that by taking advantage of reflection spectrum notches of the SSFBG en/decoder, the WDM interchannel crosstalk can be suppressed and can enable OCDMA over WDM PON to simultaneously provide multigigabit-per-second up- and downlinks to a large number of users.     

Strengthening mechanisms in nanostructured high-purity aluminium deformed to high strain and annealed

Samples of pure aluminium (99.99%) have been produced by accumulative roll-bonding to a large strain followed by a heat treatment, where a two-step annealing process has been used to produce samples with large variations in structural parameters such as boundary spacing, misorientation angle and dislocation density. These parameters have been quantified by a structural analysis applying transmission electron microscopy and electron backscatter diffraction, and the mechanical properties have been determined by tensile testing at room temperature. Strength–structure relationships have been analysed based on the operation of two strengthening mechanisms—grain boundary and dislocation strengthening—and good agreement with experiments has been found for the deformed sample. However, for samples where the density of dislocation sources has been reduced significantly by annealing, an additional strengthening mechanism, so-called dislocation source-limited hardening, may operate as a higher stress is required to activate alternative dislocation sources.