Field experiments on remediation of coastal sediments using granulated coal ash

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1–2.4 mg S L⁻¹ in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.     

Short-term flow fluctuations in Onagawa Bay,Japan, as revealed by long-term mooring observation

Short-term flow fluctuations in the southern central part of Onagawa Bay were examined using long-term mooring and hydrographic data observed during the period from May 2013 to April 2014. The short-term flow fluctuations were dominant in the periodic bands of 15–27 days and shorter than 10 days. The principal and minor components of these flow fluctuations were respectively along and across the local isobaths, which are almost parallel in the north direction. The northward flow fluctuations along the local isobaths were correlated with the northeastward wind fluctuations in both periodic bands, and these correlations were more evident from fall to winter. On the basis of these results, the northward flows are regarded as wind-induced barotropic coastal jets. On other hand, the eastward flow fluctuations across the local isobaths were related to inflow and outflow via the bay mouth or the Izushima Channel. Inflow and outflow with reverse flow at lower depths formed in summer, but those with vertically uniform flow tended to form in winter. The main summertime inflow and outflow were driven by horizontal gradients in density. These permit us to regard the main summertime inflow and outflow as gravitational circulation. Also, the summertime inflow can be intermittently caused by internal waves.     

简单线性沙丘形成环境及其动力过程研究

通过对腾格里沙漠腹地典型线性沙丘进行了三期定点监测,结合周边区域风况资料,从沙丘的形态特征、年摆动幅度及其监测断面的高程分布等对其形成环境及动力过程进行了研究。线性沙丘纵向年增高幅度达1.8 m,沙丘底部平均吹蚀深度达25 cm,脊线监测点高差可达1.13 m。沙丘底部风蚀现象比较严重,中上部位主要以积沙为主。该沙丘围绕主体走向向东摆动,沙丘脊线整体向东水平摆动距离达5.8 m。特别是沙丘顶部摆动幅度尤为明显,最大摆动幅度达到13.2 m。在沙丘K监测断面上,沙丘脊线西侧各控制点的高程呈减小趋势,沙丘主体向东侧摆动。从三次不同时期沙丘纵剖面控制点高程变化和横剖面K监测断面摆动特征来看,该线性沙丘除了受优势风向偏西风的影响外,还受东北风和西南风两股风的牵制,表现为沙丘脊线围绕主体走向左右摆动,整体向东侧平移。     

The ultra-low-frequency magnetic disturbances associated with earthquakes

The ultra-low-frequency (ULF) electromagnetic emission is recently recognized as one of the most promising candidates for short-term earthquake (EQ) prediction. This paper reviews previous convincing evidence on the presence of ULF emissions before three major EQs. Then, we present further statistical study on the ULF occurrence, our networks of ULF monitoring in different spatial scales in Japan and finally we present several signal processings to identify the seismogenic emissions by showing latest results for recent large EQs.     

Does measuring azimuthal variations in sap flux lead to more reliable stand transpiration estimates?

Stand transpiration (E) estimated using the sap‐flux method includes uncertainty induced by variations in sap flux (F) within a tree (i.e. radial and azimuthal variations) and those between trees. Unlike radial variations, azimuthal variations are not particularly systematic (i.e. higher/lower F is not always recorded for a specific direction). Here, we present a theoretical framework to address the question on how to allocate a limited number of sensors to minimize uncertainty in E estimates. Specifically, we compare uncertainty in E estimates for two cases: (1) measuring F for two or more directions to cover azimuthal variations in F and (2) measuring F for one direction to cover between‐tree variations in F. The framework formulates the variation in the probability density function for E (σ_E) based on F recorded in m different azimuthal directions (e.g. north, east, south and west). This formula allows us to determine the m value that minimizes σ_E. This study applied the framework to F data recorded for a 55‐year‐old Cryptomeria japonica stand. σ_E for m = 1 was found to be less than the values for m = 2, 3 and 4. Our results suggest that measuring F for one azimuthal direction provides more reliable E estimates than measuring F for two or more azimuthal directions for this stand, given a limited number of sensors. Application of this framework to other datasets helps us decide how to allocate sensors most effectively. Copyright © 2016 John Wiley & Sons, Ltd.     

Wells turbine with end plates for wave energy conversion

In order to improve the performance of the Wells turbine for wave energy conversion, the effect of end plate on the turbine characteristics has been investigated experimentally by model testing. As a result, it is found that the characteristics of the Wells turbine with end plates are superior to those of the original Wells turbine, i.e., the turbine without end plate and the characteristics are dependent on the size and position of end plate. Furthermore, by using a computational fluid dynamics (CFD), reason of the performance improvement of the turbine has been clarified and the effectiveness of the end plate has been demonstrated.     

Pre-Japan-ARGO: Experimental Observation of Upper and Middle Layers South of the Kuroshio Extension Region Using Profiling Floats

We deployed two profiling floats in the region south of the Kuroshio Extension in March 2000. Temperature and salinity profiles from a depth of 1500 × 10⁴ Pa to the surface are reported every two and four weeks, respectively. The floats performed very well for first four months after deployment. Later they failed in surfacing for a few months when the sea surface temperature in the region was high. The salinity sensors seemed to suffer from some damage during their failure-in-surfacing period. Despite this trouble, the results clearly demonstrate that the profiling float is a very useful and cost-effective tool for physical oceanographic observation in the open sea. This revised version was published online in July 2006 with corrections to the Cover Date.