29 research outputs found
On Capillary Path Systems In Steep Mountain Areas
This paper describes a high-density path network in a steep mountain area which supports intensive, high quality forestry in Osaka, Japan. The network, which may be likened to a capillary vessel system, makes it possible to: undertake intensive treatment of forests; effect a selective harvest of small, scattered product volumes; change the harvesting method from cable logging (which requires greater worker skill and results in high costs) to one in which products are removed from the stump area by grapple boom cranes located on roads. This network consists of a series of 2.0m wide paths which run parallel to the contour lines and a steep (but very solid) main road (2.5m wide) connecting the paths. The former are branch lines (rib paths) used primarily for extraction and the latter (which is paved with concrete) is the main line (backbone) used for access to the branch lines. In this network, the maximum gradient is 30%, the maximum height of embankment is 1.4 m, the minimum turning radius is 6 m, road density is 222.94 m/ha, correction-factor of shape V = 1.421, correction factor of real skidding distance Ô = 1.215, and the development percentage is 77.9%. Data shows that the correction factors approach 1.0 as the road density is increased, even in mountainous landforms of the type described
A deep X-ray observation of NGC 4258 and its surrounding field
We present a deep X-ray observation of the low-luminosity active galactic
nucleus in NGC4258 (M106) using ASCA. The soft X-ray spectrum <2keV is
dominated by thermal emission from optically-thin plasma with kT~0.5keV. The
hard X-ray emission is clearly due to a power-law component with photon index
Gamma=1.8 absorbed by a column density of N_H=8x10^22/cm^2. The power-law is
readily identified with primary X-ray emission from the AGN central engine. We
also clearly detect a narrow iron K-alpha emission line at 6.4keV. No broad
component is detected. We suggest that the bulk of this narrow line comes from
the accretion disk and, furthermore, that the power-law X-ray source which
excites this line emission (which is typically identified with a disk corona)
must be at least 100GM/c^2 in extent. This is in stark contrast to many
higher-luminosity Seyfert galaxies which display a broad iron line indicating a
small 10 GM/c^2 X-ray emitting region. It must be stressed that this study
constrains the size of the X-ray emitting corona rather than the
presence/absence of a radiatively efficient accretion disk in the innermost
regions. If, instead, a substantial fraction of the observed narrow line
originates from material not associated with the accretion disk, limits can be
placed on the parameter space of possible allowed relativistically broad iron
lines. By comparing our data with previous ASCA observations, we find marginal
evidence for a change in absorbing column density through to the central
engine, and good evidence for a change in the AGN flux.Comment: 11 pages, 9 postscript figures. Accepted for publication in Ap