Infrared device for simultaneous measurement of fluctuations of atmospheric carbon dioxide and water vapor

An infrared device designed to measure simultaneous fluctuations of atmospheric CO₂ and water vapor concentrations is described. The measuring frequency is 30 Hz. The sensing path length is 20 cm. It is compatible with the path length of the standard type of a sonic anemometer. The noise level of the device is equivalent to fluctuations of about 0.8 ppm peak-to-peak for CO₂ and 0.02 g kg^-1 peak-to-peak for water vapor. Field tests have showed that the device is suitable for simultaneous measurement of turbulent fluxes of CO₂ and water vapor in conjunction with a sonic anemometer.     

Shock compression of zirconia ZrO2 and zircon ZrSiO4 in the pressure range up to 150 GPa

The shock compression state of zirconia ZrO₂ and zircon ZrSiO₄ in the pressure range up to 150 GPa (1.5 Mbar) are studied on the basis of the measurements of shock velocities, particle-velocity histories, free surface motions, and electrical conductivities. Zircon transforms, and zirconia probably does, to high pressure phases up to 90 GPa. The shock velocity (U _s ) — particle velocity (U _p ) Hugoniots can be described as U _s =4.38+1.37 U _p km/s above 90 GPa for ZrO₂, and U _s =6.50+0.49 U _p km/s (mixed phase region), and U _s =1.54+2.30 U _p km/s (high pressure phase region) for ZrSiO₄. The corrected isothermal densities of the high pressure phase ZrSiO₄ are roughly consistent with the isothermal ones of mixtures of ZrO₂ and SiO₂. Bulk sound velocities in the high-pressure phase region of these oxides are discussed in comparison with other dioxides. Electrical conductivities of these oxides increase from lower than 10^?12 S/m to greater than 10⁰ S/m in the shock-stress range up to 70 GPa, and remain as constant values up to higher than 100 GPa.     

The Tsenkher structure in the Gobi-Altai, Mongolia: Geomorphological hints of an impact origin

The Tsenkher structure, in the Gobi-Altai region of Mongolia, was studied using a wide array of remote sensing data and field observations. The structure has a shallow, 3.6 km wide, central depression bordered by a near-circular ridge (putative crater rim) with breaches to the northwest. The central depression is obliterated partially by fluvial infill through these breaches. Outside the ridge, the western side is a rugged terrain, but the eastern half is characterized by a concentric outer ridge that occurs at about one radius distance from the inner ridge. Although intrusion, salt tectonics and maar crater hypotheses cannot be completely ruled out, its morphology strongly implies an impact origin for the Tsenkher structure. If of impact origin, it has a well-preserved morphology and its position in the basin fills indicates that the formation may have occurred relatively recently, sometime during the late Tertiary or Quaternary. The outer ridge morphology is similar to rampart craters on Mars, whose formation has been attributed to fluidization of a water-rich target layer and ejecta materials, or to atmospheric entrainment and deposition of ejected materials. However, other hypotheses including erosional remnant of ejecta blanket, erosional scarp of structural rim uplift, multi-ring or deeply eroded crater rim of a peak-ring crater are also possible at this stage. A complex fluvial and probable lacustrine history is envisaged within the Tsenkher structure. The structure is also associated with archaeology, including Paleolithic and Bronze Age remains.     

Spatiotemporal characteristics of interannual temperature variations in the Tsushima Strait

Spatiotemporal characteristics of interannual temperature variations in the Tsushima Strait are investigated on the basis of historical hydrographic data applying the same procedures as Senjyu et al. (2006). Empirical orthogonal function (EOF) analysis revealed that the most energetic mode of variation (the EOF first mode), which accounts for about 31.5% of the total variance, is the in-phase temperature change for the entire strait. The wintertime temperature variation described by the first mode is associated with the wintertime heat flux in the northern East China Sea, while they are poorly correlated in other seasons. The large standard deviation in the time coefficient of the first mode in August suggests a relationship with the horizontal heat advection in summer in the northern East China Sea. On the other hand, the EOF second mode, which explains about 12.6% of the total variance, is associated with the stratification and baroclinicity in the strait. The time coefficient of the EOF second mode negatively correlates with the baroclinic volume transport through the strait in summer. Comparison of temporal variations among the leading EOF modes for temperature and salinity shows no significant correlations. This indicates that the principal modes of variation in temperature and salinity vary independently within an interannual timescale.     

The role of organic haze in Titan's atmospheric chemistry: I. Laboratory investigation on heterogeneous reaction of atomic hydrogen with Titan tholin

In Titan's atmosphere consisting of N₂ and CH₄, large amounts of atomic hydrogen are produced by photochemical reactions during the formation of complex organics. This atomic hydrogen may undergo heterogeneous reactions with organic aerosol in the stratosphere and mesosphere of Titan. In order to investigate both the mechanisms and kinetics of the heterogeneous reactions, atomic deuterium is irradiated onto Titan tholin formed from N₂ and CH₄ gas mixtures at various surface-temperatures of the tholin ranging from 160 to 310 K. The combined analyses of the gas species and the exposed tholin indicate that the interaction mechanisms of atomic deuterium with the tholin are composed of three reactions; (a) abstraction of hydrogen from tholin resulting in gaseous HD formation (HD recombination), (b) addition of D atom into tholin (hydrogenation), and (c) removal of carbon and/or nitrogen (chemical erosion). The reaction probabilities of HD recombination and hydrogenation are obtained as ηabst=1.9(±0.6)×¹⁰⁻³×exp(−300/T) and ηhydro=2.08(±0.64)×exp(−1000/T), respectively. The chemical erosion process is very inefficient under the conditions of temperature range of Titan's stratosphere and mesosphere. Under Titan conditions, the rates of hydrogenation > HD recombination ? chemical erosion. Our measured HD recombination rate is about 10 times (with an uncertainty of a factor of 3-5) the prediction of previous theoretical model. These results imply that organic aerosol can remove atomic hydrogen efficiently from Titan's atmosphere through the heterogeneous reactions and that the presence of aerosol may affect the subsequent organic chemistry.     

Study on the physical disintegration characteristics of Subang claystone subjected to a modified slaking index test

Some instability problems were found on natural or engineered slopes mostly lying on Subang claystones. The instability problems included excessive erosion, slumps and rock falls. The field performance surveys of the problems suggested that the claystones physically weather rapidly so that the rock properties they exhibit during excavation often change to properties with a more characteristic of soil. Such a phenomenon is generally known as a slaking process. In order to gain better understanding about the slaking of Subang claystones, a series of experimental laboratory studies were carried out involving a modified slaking index test. Claystone samples used in this study were obtained from their exposures along the Northern West Java area of Indonesia. Petrographic analysis was correspondingly performed to identify mineral and texture/fabric, and in turn, to determine the inherent factors of the rocks which might affect the slaking process. The stssudy results indicated that the claystones were characterized by high to very high slaking properties having a maximum slaking index (I_s) of 57.4% and a mean I_s of 43.8%. Major dispersion slaking on sample surfaces and high cracking in response to excessive swelling were recognized as main slaking modes within the claystones. All samples lose progressively less material through the five wet–dry cycles of a slaking index test, indicating a decelerated slaking rate. It was evident that the main inherent factors controlling the slaking process were expandable clay mineral smectite, non-clay mineral pyrite and soluble mineral calcite. Moreover, a quite important of inherent bonding material and stress release energy in the slaking characteristics of the claystones was revealed by a closure phase of an initial hairline crack during unloading.     

Small diameter tunnel excavation method using slurry pipe-jacking

In order to protect the safety of workers construction, as well as for environmental and cost reasons, efficient small-diameter shallow tunneling methods have recently become increasingly important in regards to outside plant engineering such as for water supplies, electricity, telecommunications and gas. The effects of the above projects in overcrowded urban areas are significant and often result in substantial impact and traffic delays associated with a loss of travel time. Clearly the solution to these utility placement problems, if the full impact of trench excavation is to be avoided, is trench less technology. In particular, for construction work near existing facilities, underground tunnels that are excavated by slurry pipe-jacking are being increasingly employed in order to avoid problems. Slurry pipe-jacking was firmly established as a special method for the non-disruptive construction of the underground pipelines of sewage systems. Pipe-jacking, in its traditional form, has occasionally been used for short railways, roads, rivers, and other projects. Basically the system involves the pushing or thrusting of a drivage machine through concrete pipes ahead of jacks. This method utilizes mud slurry that is formed around the pipes in order to stabilize the surrounding soil. Moreover, in recent years, the rectangular shape of the concrete pipe in using slurry pipe-jacking was introduced due to the effective uses of the space. Based on his reason, the rectangular shape of the concrete pipe is often adopted in Japan. From this point of view, this paper discusses the effect shapes have on the stability of surrounding soil by means of the numerical analysis. Secondly, this paper discusses the performance of the mud slurry around the drivage pipes by means of the two-dimensional Eulerian-Lagragian seepage analysis. Moreover, in slurry pipe-jacking, the performance of the mud slurry plays an important role in the pushing process. Finally, the thrusts in slurry pipe-jacking can be predicted accurately by evaluating the resistance between the mud slurry and the concrete pipes and the resistance between the soil and the pipes in the curved jacking area. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analytical expressions for three different modes in harmonic motion of sliding structures

The problem of response of sliding structures subjected to harmonic support motions is considered. The periodic motions, consisting of the three different modes, stick-stick, stick-slip and slip-slip, are a significant part of the responses to harmonic excitations. Assuming the periodicity of the motion, the condition of the initiation of the slip-slip motion is derived. Then analytical expressions for the occurrence of the periodic motions are obtained without integrating the equations of motion. The accuracy of the analytical expressions is confirmed by comparison with numerical results herein obtained. It is observed that the numerical results are sensitive to the starting and ending times of slip motions.