On the simulation of the pivot bearing inside HDD

The pivot bearing is an important mechanical component in HDD. Several quasi-rigid (QR) body motion modes of the HDD are related to the stiffness of the pivot bearing such as the axial translation mode, the lateral translation mode and the rocking mode. In the shock simulation of the HDD, the pivot bearing is often simplified to identical theoretical models wherein the bearing is simulated with springs or beams. The overall axial stiffness and the radial stiffness of these models are often carefully checked and match well with the experimental values. However, how well these theoretical models represent the rotational stiffness of the bearing is still not fully understood. This is partly due to the difficulties in obtaining the experimental rotational stiffness of the pivot bearing. In this paper, three different theoretical models are examined for the simulation of the bearing. The rotational stiffness of these three theoretical models is derived analytically. The theoretical formulations are verified with the finite element analysis results.     

MFI zeolite as adsorbent for selective recovery of hydrocarbons from ABE fermentation broths

1-Butanol and butyric acid are two interesting compounds that may be produced by acetone, butanol, and ethanol fermentation using e.g. Clostridium acetobutylicum. The main drawback, restricting the commercialization potential of this process, is the toxicity of butanol for the cell culture resulting in low concentrations of this compound in the broth. To make this process economically viable, an efficient recovery process has to be developed. In this work, a hydrophobic MFI type zeolite with high silica to alumina ratio was evaluated as adsorbent for the recovery of butanol and butyric acid from model solutions. Dual component adsorption experiments revealed that both butanol and butyric acid showed a high affinity for the hydrophobic MFI zeolite when adsorbed from aqueous model solutions. Multicomponent adsorption experiments using model solutions, mimicking real fermentation broths, revealed that the adsorbent was very selective to the target compounds. Further, the adsorption of butyric and acetic acid was found to be pH dependent with high adsorption below, and low adsorption above, the respective pKa values of the acids. Thermal desorption of butanol from MFI type zeolite was also studied and a suitable desorption temperature was identified.     

Recoil-fission tagging of the transfermium nucleus 252No

An in-beam study of the transfermium nucleus ²⁵²No has been performed using the JUROSPHERE II array of germanium detectors coupled to the gas-filled recoil separator RITU. A new technique of recoil-fission tagging was used to extract tagged γ-ray data. Having significant spontaneous fission and α-decay branches, ²⁵²No is an ideal candidate for a comparative study. In a similar manner to α-decay tagging the fission events can be used to obtain γ-ray data. The recoil-fission tagged γ-ray spectrum showed a similar structure to the α-decay tagged γ-ray spectrum. By comparing the α-tagged and fission-tagged spectra and decay curves, it was shown that the spontaneous fission originates from the same initial state as the α decay. This extension of the tagging method allows in-beam spectroscopic data to be obtained from heavy nuclei with significant spontaneous-fission branches.     

Recoil Beta Tagging: Application to the study of odd-odd near proton drip line nuclei, 74Rb and 78Y

We present a study of low-spin states in ⁷⁴Rb and ⁷⁸Y using the new technique of Recoil Beta Tagging. This yielded new information on ⁷⁴Rb and has provided the first evidence for non-isomeric T= 1 states in ⁷⁸Y.     

Population Monotonic Allocation Schemes in Bankruptcy Games

The USA Bankruptcy Code legislates the bankruptcy of firms. Any allocation mechanism that is legal according to the Bankruptcy Code is necessarily population monotonic. Bankruptcy rules yielding a population monotonic allocation scheme in the associated bankruptcy game are characterized by efficiency, reasonability (each claimant receives a nonnegative amount not exceeding his claim), and the thieve property. The thieve property for bankruptcy problems entails that if a claimant manages to escape with his claim, the amount allocated to each remaining claimant is not larger than his share in the original problem. Many bankruptcy rules studied in the literature are efficient, reasonable, self-consistent, and monotonic. Rules satisfying these axioms are shown to yield population monotonic allocation schemes.     

Zeolite coated ATR crystals for new applications in FTIR-ATR spectroscopy

Thin silicalite-1 films were grown on ATR crystals and used for detection of low amounts of organic molecules in a gas flow by FTIR spectroscopy.     

Alpha-decay studies of the new isotopes 191At and 193At

Detailed alpha-decay studies have been performed for the neutron-deficient isotopes ¹⁹¹At and ¹⁹³At. The nuclei were produced in fusion-evaporation reactions of ⁵⁴Fe and ⁵⁶Fe ions with a ¹⁴¹Pr target. The fusion products were separated in-flight using a gas-filled recoil separator and implanted into a position-sensitive silicon detector. The isotopes were identified using position, time and energy correlations between the implants and subsequent alpha-decays. Three alpha-decaying states were identified for ¹⁹³At and two for ¹⁹¹At. The spin and parity of the initial states in the astatine isotopes were deduced based on unhindered alpha-decays to states in the bismuth daughter nuclei. In both astatine isotopes the 1/2⁺ intruder state was determined to be the ground state and a 7/2^- state to be the first-excited state. In ¹⁹³At the alpha-decay of the 13/2⁺ state was observed in coincidence with a previously known gamma-ray transition from the 13/2⁺ state in the corresponding daughter nucleus ¹⁸⁹Bi. In ¹⁸⁷Bi and ¹⁸⁹Bi low-lying 7/2^- states were observed for the first time via alpha-decay of the mother nuclei.Received: 16 December 2002, Revised: 26 March 2003, Published online: 4 August 2003PACS: 23.60.+e Alpha decay - 27.80.+w - 23.20.Lv transitions and level energies - 21.10.Dr Binding energies and masses     

Heavily carbon-doped GaAs grown on various oriented GaAs substrates by MOMBE

Heavily carbon-doped GaAs epitaxial layers have been grown simultaneously on (100), (111)A, (111)B, (411)A, (411)B and (711)A semi-insulating (SI) GaAs substrates by metalorganic molecular beam epitaxy (MOMBE) using trimethylgallium (TMG) and elemental As (As₄). The hole concentration and surface flatness strongly depend on the substrate orientation. The highest carbon incorporation was observed for the layers grown on a (411)A substrate with a hole concentration of 1.0 × 10²¹ cm^{− 3} and a lattice mismatch of Δd/d = −0.48%. Atomic force microscope (AFM) images reveal that the epilayers grown on (411)A substrates exhibit extremely flat surfaces, although these layers contain the highest carbon concentration.     

Influence of growth related thickness fluctuations on the spectral and lateral luminescence intensity distribution in GaAs quantum wells

The effect of low energy exciton sinks on the spectral and spatial luminescence intensity distribution has been investigated in a single quantum well (QW) and a multiple QW structure prepared by growth interrupted molecular beam epitaxy (MBE). Both samples contain growth-related lateral variations of the exciton confinement energy on the order of the exciton diffusion length, which cause a lateral and spectral intensity distribution in cathodoluminescence images.