Sticking in moderate velocity oblique impact: Application to planetology

The sticking behavior of metal—metal collisions in the velocity range ～50–650 m/sec—has been investigated experimentally. A map of sticking efficiency versus impact angle and impact velocity has been established for lead. The threshold sticking velocity for normal impact equals approximately 100 m/sec for lead, 140 m/sec for tin, and 500 m/sec for iron in the case of spherical projectiles of 8-mm diameter, and a semi-infinite target. The boundary between the plastic rebound area and the perfect sticking area is found to be a line of constant normal velocity. The case when projectile mass is equal to target. ass ($\text{?3}\text{g}$, lead) has been investigated as well. The experimental results have been extrapolated to higher temperature and then applied to iron, nickel, and magnesium silicate. Near the melting point ($\text{?1800°}\text{K}$), the sticking velocities were estimated as 250–350 m/sec for iron and nickel and about 40% higher for magnesium silicate. It was concluded that metals stick more easily than rocky materials because of their lower sticking velocity and much larger interval of temperature over which sticking is possible.     

On the mass determination of collapsed objects in close binaries: Applications to black-holes and neutron stars

Observational information required for determination of the masses of collapsed objects in close binaries is examined. Assumptions commonly used to evaluate the masses or thier lower limits, in the absence of the required observational data, are critically discussed. A reliable determination of the mass of a collapsed object in X-ray emitting binaries is yet to be made. No definitive case has been made for or against the existence of a black-hole in CygX-1.     

On the Concentrations of the Dissolved Chemical Elements in the Estuary Water of the Chikugogawa River

When river water mixes with sea water in estuary area, the concentrations of the dissolved element in river water may be changed by either a simple physical mixing process or some complex chemical processes. It has been clarified in the Chikugogawa River estuary area that the change in concentrations of SO ₄ ²⁻ , BO ₃ ³⁻ , Mg²⁺, Ca²⁺ and F⁻ is only due to the mixing process but the change in concentrations of SiO ₃ ²⁻ and Al³⁺ is due to the chemical process in addition to the mixing process.      

Simultaneous Measurement of Hydrogen Peroxide and Fe Species (Fe(II) and Fe<Subscript>(tot)</Subscript>) in Okinawa Island Seawater: Impacts of Red Soil Pollution

The northern part of Okinawa Island suffers from red soil pollution—runoff of red soil into coastal seawater—which damages coastal ecosystems and scenery. To elucidate the impacts of red soil pollution on the oxidizing power of seawater, hydrogen peroxide (HOOH) and iron species including Fe(II) and total iron (Fe_(tot), defined as the sum of Fe(II) and Fe(III)) were measured simultaneously in seawater from Taira Bay (red-soil-polluted sea) and Sesoko Island (unpolluted sea), off the northern part of Okinawa Island, Japan. We performed simultaneous measurements of HOOH and Fe(II) because the reaction between HOOH and Fe(II) forms hydroxyl radical (•OH), the most potent environmental oxidant. Gas-phase HOOH concentrations were also measured to better understand the sources of HOOH in seawater. Both HOOH and Fe(II) in seawater showed a clear diurnal variation, i.e. higher in the daytime and lower at night, while Fe_(tot) concentrations were relatively constant throughout the sampling period. Fe(II) and Fe_(tot) concentrations were approximately 58% and 19% higher in red-soil-polluted seawater than in unpolluted seawater. Gas-phase HOOH and seawater HOOH concentrations were comparable at both sampling sites, ranging from 1.4 to 5.4 ppbv in air and 30 to 160 nM in seawater. Since Fe(II) concentrations were higher in red-soil-polluted seawater while concentrations of HOOH were similar, •OH would form faster in red-soil-polluted seawater than in unpolluted seawater. Since the major scavenger of •OH, Br⁻, is expected to have similar concentrations at both sites, red-soil-polluted seawater is expected to have higher steady-state •OH concentrations.     

Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit

We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque), and III (transparent). Scanning electron microscopy combined with electron backscattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot elastic limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~10 GPa) to melting pressure (~100 GPa) in a hierarchical order.     

Map projection errors in the Weber problem

 When demand points are given as a planar map where projection method is explicitly stated, we usually know the latitudes and longitudes of these points from the map. Then we can solve the Weber problem on the globe, and we do not suffer from errors. This paper analyses how cylindrical projections cause distortion in the Weber problem when demands are distributed on the Northern Hemisphere. First, we demonstrate that planar solutions are always located south of the spherical solution if the Mercator projection, the equirectangular projections with standard parallels near the demands, or the equal-area projection with the same characteristic is chosen. Second, we verify that this geographical tendency is inclined to hold when the demand points, are distributed symmetrically, widely or toward the north. Received: 15 August 2001 / Accepted: 20 April 2002 This paper was partially written while the first author was visiting the Department of Geography at the Catholic University of Louvain, Louvain-la-Neuve, Belgium [1993–1994]. He is grateful for the hospitality of this department. An earlier version of this paper was presented in 1994 at the Seventh Meeting of the European Operational Research Working Group on Locational Analysis in Brussels, and in 1996 at the Fifth World Congress of the Regional Science Association International in Tokyo. The authors would also like to thank the participants as well as three anonymous referees for their constructive comments.     

Inland penetration of the sea breeze over the suburban area of Tokyo

Observational results of the structure of the sea breeze over the urban and suburban areas of Tokyo for four summer days are presented.On two of these days, the inland penetration of the sea breeze front could be clearly traced. In one case, the sea breeze was first observed along the shores of Tokyo Bay around 0900 JST, and propagated in three hours through the Tokyo City area, the width of which is about 20 km. It then advanced inland at a rate of 16 km h^–1. Prior to the arrival of the sea breeze at the suburban site, the mixing height had remained at about 600 m for four hours. With the arrival of the sea breeze front, accompanied by an abrupt change in wind speed and direction, the mixing height increased sharply to 1700 m. It is suggested that this behavior and the structure of the front are intensified due to the urban effect, or the difference in the thermal characteristics between the urban and rural areas.On the days without a sea breeze front, the land breeze system during the early morning was less intense, allowing the sea breeze to develop simultaneously with the inland valley wind and easily form a large-scale local wind system during the morning hours. In both cases, the vertical motion accompanying the local wind system works as a feedback mechanism to control the local winds by modifying the thermal and pressure fields.     

The selectivity of the Ioannina VAN station

Two peculiar characteristics of the VAN method of short-term earthquake prediction are: (1) the existence of sensitive and insensitive sites to seismic electric signal (SES) and (2) the selective sensitivity of a sensitive station to SES from specific focal area(s). The process of their discovery, which so far has not been published adequately, is examined for the Ioannina (IOA) station. The sensitive site was discovered simply through repeatedly moving the temporary observation network. The selectivity map of the IOA station was made by first identifying the earthquake source areas with SESs which were considered to have been detected at IOA, and second by examining the direction of SESs from different such source areas. For the latter purpose, information from long dipoles appears to have been helpful. The selectivity map is empirically constructed and is updated regularly. We have independently tried to construct a selectivity map of IOA by examining VAN's raw SES records and by using the same criteria as VAN. The selectivity map we obtained was not exactly, but roughly similar to that of VAN.     

Roughness length for heat over an urban canopy

The roughness length for heat z_T was evaluated over an urban canopy, using the measured sensible heat flux and radiometric temperature. To overcome thermal heterogeneity in the urban area, the measured radiometric temperature was transformed into the equivalent temperature of an upward longwave radiation flux. The equivalent temperature was found to provide an effective parameterization of the radiometric temperature. The daytime average of the resulting ln(z_T/z₀) was 10, where z₀ is the aerodynamic roughness length. This result generally agrees with previous studies; however, the anthropogenic heat is a large uncertainty, which could cause an error at least 240% in z_T.