Geometric effect of angle of repose revisited

We report on a universal pattern observed in the collapse dynamics of a sand heap. Collapse dynamics of a three-dimensional sand heap were studied through experiments and numerical simulations. A phenomenological law that describes the shape of a collapsed sand heap was found, we call this the geometric constitutive law of friction. The law is summarized as the linear relation between the frictional coefficient and the local horizontal curvature.     

Polyimide film containing ultra-fine particles

We have succedded in fabricating a polyimide film with a molecular alignment superior to that obtainable by the conventional rubbing treatment. This phenomenon is realized by means of the dispersion of ultra-fine particles such as carbon and titanium dioxide in the polyimide precursor prior to the fabrication of the polyimide film and the rubbing treatment. The molecular alignment was evaluated with birefringence and infrared dichroism measurements. Further experiments establishe that the adsorption of polyimide molecules on ultra-fine particles is a significant factor in achieving a large orientational anisotropy. A model of the alignment is presented in which the rubbing treatment induces the particles to traverse the surface of the film, causing polyimide molecules adsorbed on them to be elongated in the rubbing direction. A potential application of oriented polymide films is the homogeneous alignment of nematic and smectic liquid crystals.     

3D FLOW INSIDE BUBBLE-TYPE VORTEX BREAKDOWN: AN EXPERIMENTAL INVESTIGATION VIA LDV

1 .　INTRODUCTIONRichvortex phenomenahavebeenfoundinrotatingflows ,suchassecondaryflowandvortexbreakdown .Alargequantityofexperimentalandnumericalinvestigationshasbeendonetogainin sightintovortexdynamicsandtheir generationmechanism .However ,physicsforunderstandingthevortexdynamicsespeciallyvortexbreakdownisstilllimitedtoagreatextent.Toclarifyitsstruc tureanddynamics ,verysmallexternaldisturbanceandveryfinegridarrangementarenecessaryforexperimentalmeasurement.Thenvaliddatawithalloweduncer…     

Effect of microstructure of simulated heat‐affected zone on low‐ to high‐cycle fatigue properties of low‐carbon steels

To clarify the effect of microstructural changes on the fatigue property of the weld heat‐affected zone (HAZ), low‐ to high‐cycle fatigue tests were conducted on 16 types of simulated HAZ specimens that had been prepared using thermal processes. The results showed the fatigue S‐N curves of the HAZ to be widely scattered as a function of strength level. These fatigue data were divided into two groups: coarse grain (CG) and fine grain (FG) HAZ, when strain amplitude was used to represent S‐N curves. The fatigue data for the CGHAZ group showed a relatively short fatigue life. Based on surface observations, the initiated fatigue crack size of CGHAZ was larger than that of FGHAZ as a function of microstructural unit size. Hence, fatigue crack growth life, which is almost the same as total fatigue life of CGHAZ, decreased.     

Investigating risk factors for slips, trips and falls in New Zealand residential construction using incident-centred and incident-independent methods

Slip, trip and fall (STF) incidents, particularly falls from a height, are a leading cause of injury in the New Zealand residential construction industry. The most common origins of falls from a height in this sector are ladders, scaffolding and roofs, while slipping is the most frequent fall initiating event category. The study aimed to provide detailed information on construction industry STF risk factors for high-risk tasks, work equipment and environments, as identified from an earlier analysis of STF claims data, together with information to be used in the development of interventions to reduce STF risk in New Zealand residential construction. The study involved the use of both incident-centred and incident-independent methods of investigation, including detailed follow-up investigations of incidents and observations and interviews with workers on construction sites, to provide data on a wide range of risk factors. A large number of risk factors for residential construction STFs were identified, including factors related to the work environment, tasks and the use and availability of appropriate height work equipment. The different methods of investigation produced complementary information on factors related to equipment design and work organization, which underlie some of the site conditions and work practices identified as key risk factors for residential construction STFs. A conceptual systems model of residential construction STF risk is presented.     

A new spin cast process for mass-production of polycrystallinesilicon sheets

A spin cast process for producing polycrystalline silicon sheets for low-cost and high-efficiency solar cells and equipment for its application to mass production are discussed. This process makes it possible to produce high-quality silicon sheets with a production rate of 15 s/sheet. A maximum solar cell efficiency of over 13% is obtained. To reduce production time, a crystal growth zone occurs in the equipment between the spinning zone and the cooling zone. The crystal grows after the spinning process with a physical growth rate of 20 mm/min when mold modules in the crystal growth zone are transferred to the cooling zone     

Contributing factors in construction accidents

This overview paper draws together findings from previous focus group research and studies of 100 individual construction accidents. Pursuing issues raised by the focus groups, the accident studies collected qualitative information on the circumstances of each incident and the causal influences involved. Site based data collection entailed interviews with accident-involved personnel and their supervisor or manager, inspection of the accident location, and review of appropriate documentation. Relevant issues from the site investigations were then followed up with off-site stakeholders, including designers, manufacturers and suppliers. Levels of involvement of key factors in the accidents were: problems arising from workers or the work team (70% of accidents), workplace issues (49%), shortcomings with equipment (including PPE) (56%), problems with suitability and condition of materials (27%), and deficiencies with risk management (84%). Employing an ergonomics systems approach, a model is proposed, indicating the manner in which originating managerial, design and cultural factors shape the circumstances found in the work place, giving rise to the acts and conditions which, in turn, lead to accidents. It is argued that attention to the originating influences will be necessary for sustained improvement in construction safety to be achieved.     

Occlusion of the cervical internal carotid artery due to a dog bite wound: case report

A rare case of traumatic occlusion of the carotid artery at the neck caused by a dog bite is reported. A 10-year-old boy presented delayed onset of left hemiparesis after a dog-bite wound in the right neck. CT scan revealed a cerebral infarction in the right basal ganglia, and IV-DSA disclosed complete occlusion of the right internal carotid artery at the neck. The patient was treated conservatively and his left hemiparesis improved, but impaired visual acuity remained on the right side. Repeated IV-DSA 12 days later showed recanalization of the right internal carotid artery. The mechanisms of the traumatic occlusion of the internal carotid artery were discussed with reference to the literature.     

The role of rolling friction in granular packing

In order to study the effects of the rolling friction of the particles on granular packing, we present a detailed analysis of circular disk assemblies with the rolling friction under macroscopic one-dimensional compression. The rolling friction of the particles produces a resisting moment to the rolling at each contact. A series of 2-D DEM simulations are performed with various values for the rolling friction parameter. We focus on several macroscopic and microstructural properties of granular media and analyze them as a functions of the rolling friction. From these results, we show that the rolling resistance, which results from the rolling friction of the particles, contributes to the inhibition of the rearrangement of the particles and increases the magnitude of the fabric anisotropy under packing. In addition, from both microscopic and macroscopic points of view, we describe that the stress state in a granular packing can vary considerably depending on the rolling resistance.