Adaptive Q control for tapping-mode nanoscanning using a piezoactuated bimorph probe

A new approach, called adaptive Q control, for tapping-mode atomic force microscopy (AFM) is introduced and implemented on a homemade AFM setup utilizing a laser Doppler vibrometer and a piezoactuated bimorph probe. In standard Q control, the effective Q factor of the scanning probe is adjusted prior to the scanning depending on the application. However, there is a trade-off in setting the effective Q factor of an AFM probe. The Q factor is either increased to reduce the tapping forces or decreased to increase the maximum achievable scan speed. Realizing these two benefits simultaneously using standard Q control is not possible. In adaptive Q control, the Q factor of the probe is set to an initial value as in standard Q control, but then modified on the fly during scanning when necessary to achieve this goal. In this article, we present the basic theory behind adaptive Q control, the electronics enabling the online modification of the probe's effective Q factor, and the results of the experiments comparing three different methods: scanning (a) without Q control, (b) with standard Q control, and (c) with adaptive Q control. The results show that the performance of adaptive Q control is superior to the other two methods.     

Investigations on the variation of corrosion and contact resistance characteristics of metallic bipolar plates manufactured under long-run conditions

Tribological variations, surface conditions (roughness, hardness, coating) and surface interactions between micro-stamping dies and bipolar plate blanks play a critical role in determining the surface quality, channel formation and precision of bipolar plates. This study is aimed to understand the cause, mechanism and consequences of interactions between micro-stamping process conditions and bipolar plate quality. A total of 2000 repeated micro-stamping of 51 μm-thick uncoated and 1 μm-thick ZrN coated SS316L sheet blanks into an array of 750 μm micro-channels were performed using 175-220 kN force levels with constant stamping speed of 1 mm/s. Microscopic examinations were conducted periodically on both die and coated & uncoated plate surfaces to observe topographic variations. In addition, corrosion and contact resistance tests were carried out in the same intervals. Analysis of variance (ANOVA) technique was used to determine the significance of the process parameters on channel height, roughness, corrosion and contact resistance differences. The results revealed similar roughness trends for die and plate surfaces during 2000 micro-stampings. ZrN coating with 1 μm thickness dramatically improved corrosion and contact resistance behavior of plates.     

Processing sulfate viscose cellulose prepared using oxygen in bleaching

Conclusions -- Two lots of cellulose, from pine wood and from larch, have been developed; these were treated in the first stage of bleaching with oxygen in alkaline medium instead of by chlorination, under experimental conditions.-- From a preliminary evaluation, the process of viscose preparation and preparation of the viscose for spinning under experimental conditions took place without significant deviations from the accepted technological regime. Higher technological indices of the viscose from pine cellulose were noted.-- The process of spinning viscose fibre from experimental lots of viscose from larch wood and from pine took place in a stable fashion; no clogging of the spinnerets was observed.Translated from Khimicheskie Volokna, No. 5, pp. 17–19, September–October, 1990.     

Various types of suprameatal spines and depressions in the human temporal bone

Since it covers the lateral wall of the mastoid air system, the suprameatal triangle is of importance to otologic surgeons during mastoidectomy. Because of this clinical importance, topographic anatomy of the suprameatal spine and depression was studied on Anatolian skulls. In all, 363 male and 231 female skulls were studied. The most prevalent type of suprameatal spine resembled a crest and was found in both sexes on the right (77.6%) and left (80%) sides. The absence of a suprameatal depression was significantly higher in females (right 9.1%; left 8.7%) than in males (right 1.7%; left 2.5%). Suprameatal depressions were mostly shallow in female subjects, but were mostly observed in males to be at a medium depth or deep.     

Real-time implementation of finite control set model predictive control for matrix converter based solid state transformer

Solid state transformer formed by back-to-back connection of two three-to-single-phase matrix converter, so called MC-SST, owns ac–ac power conversion in a single stage and an absence of the bulky line-frequency transformer when linking ac sources of different voltage amplitudes and frequencies. Current modulation methods for this topology include sophisticated computation of current and voltage vectors besides duty cycle composition. Moreover, extra control design is required to manage the power exchange. In this paper, the easy-to-perform finite control set model predictive control (FCS-MPC) for this type of MC-SST is implemented in real-time platform and compared with the proportional–integral control strategy. The active power changes, different voltage amplitudes and phases, and parameter variations are investigated. Simulation and real-time implementation results demonstrate the simplicity and validity of the MPC approach for power management of the MC-SST system.