Effects of 4He impurities on 3He nuclear spin-lattice relaxation in hcp solid 3He

Nuclear spin-lattice relaxation properties of hcp solid ³He with ⁴He impurities have been studied. At temperatures below the exchange plateau region, three kinds of relaxation time were observed. To analyze the data, a phenomenological four-bath model was developed, the four baths being the Zeeman bath, the phonon bath, an X-bath, and a Y-bath. The X-bath consists of the exchange bath and a part of the ⁴He-⁴He elastic interaction bath. The Y-bath is the main part of the elastic interaction bath. We measured the concentration dependence of the energy constants of all the baths, as well as the temperature and concentration dependences of the three kinds of relaxation time. The relaxation behavior corresponding to the process between the X-bath and the Y-bath could not be expressed by a single exponential function of time and the relaxation rate was strongly dependent on the concentration. This process may be related to the internal thermal equilibrium process within the elastic interaction bath. The impurity-dependent relaxation time between the X-bath and the phonon bath had a temperature dependence of T ^–n with n = 7.4±0.3.     

Investigating the multi-causal and complex nature of the accident causal influence of construction project features

Construction project features (CPFs) are organisational, physical and operational attributes that characterise construction projects. Although previous studies have examined the accident causal influence of CPFs, the multi-causal attribute of this causal phenomenon still remain elusive and thus requires further investigation. Aiming to shed light on this facet of the accident causal phenomenon of CPFs, this study examines relevant literature and crystallises the attained insight of the multi-causal attribute by a graphical model which is subsequently operationalised by a derived mathematical risk expression that offers a systematic approach for evaluating the potential of CPFs to cause harm and consequently their health and safety (H&S) risk implications. The graphical model and the risk expression put forth by the study thus advance current understanding of the accident causal phenomenon of CPFs and they present an opportunity for project participants to manage the H&S risk associated with CPFs from the early stages of project procurement.     

Time dependence of mesoscopic strain distribution for triaxial woven carbon-fiber-reinforced polymer under creep loading measured by digital image correlation

This paper presents the time dependence of the mesoscopic strain of a triaxial woven carbon-fiber-reinforced polymer under creep loading measured using digital image correlation (DIC). Two types of DIC techniques were employed for the measurement: conventional subset DIC and mesh DIC. Static tensile and creep tests were carried out, and the time dependence of the mesoscopic strain distribution was investigated by applying these techniques. The ultimate failure of this material is dominated by inter-bundle decohesion caused by relative rigid rotation and relating shear stress. Therefore, these were focused on in the present study. During the creep tests, the fiber directional strain, shear strain, and rotation were monitored using the DIC, and the mechanism for the increase in the specimen’s macro-strain over time was investigated based on the results obtained by the DIC measurement.     

Acoustic Resonance in Exhaust Gas Economizer Tube Bundles Prediction and Suppression of Resonance

The tendency for air column resonance generation in structures with a constant volume behind a tube array like that of an exhaust gas economizer has been reported, but many points remain unclear with respect to the mechanism and conditions that generate acoustical resonance. When acoustical resonance is generated, in reality, prevention and suppression measures are implemented by inserting a baffle plate into the ducts through a process of trial and error. The purpose of this study is to clarify the mechanism of generation of acoustical resonance, and to establish an appropriate measure to prevent such resonance. Noise generated in an exhaust gas economizer was correlated with the flow inside the tube array and experimentally analyzed, and the mechanism for resonance generation was considered. In addition, the effectiveness of a baffle plate positioned in order to prevent resonance was investigated. We have successfully employed a single baffle plate to suppress resonance.     

Feasibility of zeolites in converting butyric acid into propylene for biorefineries

The biorefinery has been recognized as a new industry to produce both energy and chemical materials such as olefins and BTX from renewable resources. In this context the conversion of butyric acid over zeolites was investigated for establishing a new production route of propylene. Propylene was mainly generated by decarbonylation and dehydration of butyric acid. Our study proved that H-ZSM-5 (750) and silicalite were the best industrial catalyst among the tested ones. For H-ZSM-5 (750), the selectivity of propylene reached 64.2 C% and the ratio of the yield for propylene to theoretical yield (75 C%) became 85.6%.     

Nanosized‐Layered LiVO2 Prepared from Peroxo‐Polyvanadic Acid and Its Electrochemical Properties

Nanosized‐layered rock‐salt LiVO₂ was prepared by a new method from peroxo‐polyvanadic acid. The X‐ray diffraction pattern was well fitted with the space group R?3m in the Rietveld analysis and the crystallite size was estimated at 47 nm. The electrochemical properties as cathode materials for lithium ion batteries were investigated. The specific capacity of LiVO₂ was greatly improved to 149 mAh/g under the current density of 149 mA/g, in comparison with that of the conventional LiVO₂ below 50 mAh/g prepared by the solid‐state reactions.     

Chemical vapor deposition of boron- and nitrogen-containing graphene thin films

Boron and nitrogen-incorporated graphene thin films were grown on polycrystalline Ni substrates by thermal chemical vapor deposition using separate boron- and nitrogen-containing feedstocks. Boron and nitrogen atoms were incorporated in the film in almost equal amounts and the total content reached ∼28%. The film predominantly consisted of separate graphene and boron nitride domains. Carrier concentration in the graphene domains was estimated to be about 1 × 10⁻³ e/atom (3.8 × 10¹² cm⁻²) from G band shift in Raman spectra.     

Mitigating the health and safety influence of subcontracting in construction: The approach of main contractors

Subcontracting is noted for its adverse health and safety (H&S) influence in construction. Using interviews with five of the top 20 UK contractors and one medium-sized contractor, this study explored how main contractors manage the H&S influence of subcontracting with a focus on their in-house measures. Some in-house measures found are: restricting the layers of subcontractors on projects; working with a regular chain of subcontractors; implementing a H&S reward scheme for subcontractors; and insisting on non-working subcontractor foremen who have direct responsibility for the safety of workers in their trade. These measures appear to be influenced by clients, industry peer groups, and the moral justification for occupational H&S, and they offer inter-organisational learning opportunities for contractors in devising measures to mitigate the H&S influence of subcontracting. These findings should also allay concerns that removing some of the legislative hurdles in connection with on-going red tape debate will result in poorer H&S.