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Phytolith and macroscopic charcoal in cumulative soils on the Soni Plateau, Central Japan, were evaluated to clarify the Holocene history of intentional fires and grassland development, and to compare the findings with those derived from pollen and charcoal records in sediments taken from a nearby mire in the previous study. Prior to ~1500 cal. BP, Bambusoid short-cell phytoliths and Pleioblastus-type and Bambusoideae-type bulliform cell phytoliths were abundant with scarce charcoal particles (<1000 particles/cm3). In contrast, since ~1500 cal. BP Andropogoneae-type bulliform cell phytoliths and Bilobate short-cell phytoliths were dominant with abundant charcoal particles (>1000 particles/cm3). Based on correlating these records with pollen and charcoal records in mire sediments, prior to ~1500 cal. BP, dwarf bamboo flourished on the forest floor under largely fire-free conditions, whereas since ~1500 cal. BP, grassland dominated by Japanese pampas grass has been sustained by periodic intentional burning that has continued until the present day. © The Author(s) 2011. Source


Kog Y.C.,West Japan Engineering Consultants Inc.
International Journal of Geomechanics | Year: 2016

The interaction of an applied axial load and a drag load on a circular pile in consolidating layered soil is investigated. A rigorous load-transfer theory with elastoplastic slip considered at the pile-soil interface for such piles is developed. The validity of the proposed solution is confirmed by a comparison with field measurements. Results of extensive parametric studies with regard to the pile behavior are presented for a better understanding of the behavior for axially loaded piles embedded in layered soil with an upper consolidating layer. Design charts are presented to predict the location of the neutral plane, maximum pile load, and pile top settlement for axially loaded piles in layered consolidating soils. © 2015 American Society of Civil Engineers. Source


Kog Y.C.,West Japan Engineering Consultants Inc. | Loh P.K.,National University of Singapore
Journal of Construction Engineering and Management | Year: 2012

The present study attempts to distinguish the different critical success factors (CSFs) for different components of construction projects as perceived by different professions, i.e.,civil and structural engineers, mechanical and electrical engineers, architects, and quantity surveyors. An analytical hierarchy process (AHP) is adopted to solicit the consistent subjective judgment of 27 experts in construction to identify the top 10 CSFs from 67 factors describing aspects of project characteristics, contractual arrangements, project participants, and interactive processes. The views of the different professionals are shaped by the experience they gained from their involvement in the respective components of the construction projects under their charge. It follows that the CSFs identified by the professionals are naturally relevant to the components of construction projects that they are familiar with. The present study reveals that the respective top 10 CSFs for the schedule, budget, and quality performance of architectural works, civil and structural works, and mechanical and electrical engineering works are markedly different. Moreover, the study shows that the judgment with regard to CSFs of respondents with less than 15years of experience differs from that of the more experienced respondents and hence may not be good enough. It follows that studies reported in the existing literature that have included views of respondents with less than 15years' experience in construction or based on the views of professionals predominantly from a particular discipline are likely to be biased and misleading. © 2012 American Society of Civil Engineers. Source


Kog Y.C.,West Japan Engineering Consultants Inc.
Journal of Performance of Constructed Facilities | Year: 2014

A completed car park canopy collapsed shortly after its completion. The structural system of the car park canopy was a T steel structure of unequal cantilevers connected to the ground at the base with eight 25-mm anchor bolts. The collapse was a progressive one starting with the steel structure located at one end of the roof. An investigation of the causes of collapse was carried out. Before the collapse, the maximum tension acting on an anchor bolt was not more than 10% of the tensile strength of the bolt. This investigation shows that the use of incompatible bolts and nuts such as in the case reported lead to the total loss of the tension capacity of anchor bolts in 3 days. © 2014 American Society of Civil Engineers. Source


Belaud G.,Montpellier SupAgro | Litrico X.,Research and Development Center | Clemmens A.J.,West Japan Engineering Consultants Inc.
Journal of Irrigation and Drainage Engineering | Year: 2013

Estimating the response time of a canal is essential for the open-loop control of an irrigation canal since upstream flow releases must be anticipated to satisfy scheduled demands at irrigation outlets. The authors consider a flow release at the upstream end of a pool to satisfy a side withdrawal at its downstream end. When the flow is released, wave travel time causes the flow change to arrive sometime later downstream, and attenuation causes the flow to arrive gradually downstream such that the peak discharge is further delayed. A clear definition of this response time is proposed based on volume compensation. A linear approach is used to calculate the canal response to a flow release and a withdrawal and then the volume passing at the downstream end of the canal. The approach provides an analytical determination of the time of opening that ensures volume compensation. A practical method to derive this response time is proposed. It is illustrated for a canal for which different downstream boundary conditions are imposed. © 2013 American Society of Civil Engineers. Source

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