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The first X-band dual polarized phased array weather radar (DP-PAWR), which simultaneously transmits pulses of horizontal and vertical polarized radiation, was developed and installed at Saitama University, Japan, in December 2017. The DP-PAWR uses mechanical and electronic scanning at azimuth and elevation angles, respectively. It provides polarimetric precipitation measurements via 3-D volume scanning with an update rate between 10 and 60 s, for a range of up to 80 km. Here, we describe the initial DP-PAWR observation results. To evaluate the DP-PAWR observation accuracy, we compared the observational data with radar variables derived from Parsivel disdrometer data. In comparison with the disdrometer, the relative observation accuracy for the DP-PAWR radar reflectively factor had a standard deviation of 1.1 dB and mean value of 0.4 dB. We also conducted detailed observations of a developing thunderstorm using a specific differential phase ( $K_{\mathrm {dp}}$ ) column, focusing on the $K_{\mathrm {dp}}$ core during the storm. The $K_{\mathrm {dp}}$ core movements provided useful information about the convection flow during the storm.

Evaluation of the deformation behavior due to drying is crucial in underground construction works. Especially, geological repository for High-Level Radioactive Waste (HLW) shall be carefully selected to act as a natural barrier to prevent radioactive nuclide leaks. Uniaxial Compressive Strength (UCS) is one such governing factors when designing or selecting a suitable location for such underground storage compartments or access tunnels. Since nuclide leakage through geological repositories, intact rocks UCS will vary with the drying conditions. Hence, it is vital to evaluate the behavior of UCS subject to the conditions prescribed. A variety of statistical models has been built to govern the interdependency between UCS and water content. However, there are no significant amount of research have been conducted to emphasize the UCS variation with the degree of saturation under the influence of drying condition. Numerically, Richard’s equation exact solution in Neuman boundary condition has been derived to exploit the degree of saturation with respect to time and position. Experimentally, obtain the UCS variation with the degree of saturation pertaining to the Neogene Tuff in Utsunomiya city, Japan. A best fit statistical model was generated for experimental data between UCS variation and the degree of saturation. Then, the experimental saturation degree was replaced by Richard’s equation exact solution saturation degree values. Surprisingly, produced graphs for experimental data and numerical analysis data for exact solution were perfectly overlapped. Results point out that change of UCS shows similar characteristics, which exponentially decrease, with both experimental saturation values and exact solution saturation values influenced the drying condition. Moreover, it suggests that UCS value can be predicted subject to the time and position in the sedimentary rocks under drying conditions.

Deformation characteristics of sedimentary rocks significantly changed with the water content during drying. In tunnel construction, extremely small displacements such as geological disposal, are a...

In addition to changes in the deformation characteristics of rock masses based on the water content, significant deformation occurs in sedimentary rocks from saturation to drying. In tunnel constru...

This paper is an overview of a project concerned with “Early warning for torrential rainfall/tornado” under “Enhancement of Societal Resiliency against Natural Disasters,” which is one of eleven themes of the SIP (Cross-ministerial Strategic Innovation Promotion Program under the Council for Science, Technology and Innovation, the Cabinet Office, Government of Japan). The characteristics of the project are the development of a multi-parameter phased array weather radar (MP-PAWR) that enables the accomplishment of an accurate three-dimensional model of precipitation over 30 s within a 60 km radius. Various products developed ducts using MP-PAWR and other observations, and numerical predictions, are also discussed, with a demonstration experiment to provide early warnings for torrential rainfall and related disasters. For end users such as local governments and general citizens, the final goal of this project is the social implementation of these products.

This paper presents a study on the use of piezoelectric transducers as inductive elements for a 2–4 phase resonant electrostatic induction motor. A model for transducer impedance is presented and coupled to known motor characteristics to determine how to combine a given motor to a given transducer. This is substantiated with experimental measurements. Experimental verification of motor resonance was also performed, with successful results, despite some error and observation of non linear behavior. Motor thrust force was also measured, with the motor having producing around 300 mN, very close to the expected force output.

Electrostatic film actuators, which are flexible and light-weight linear motors, can possibly realize safe contact between the robot and environments, if adopted for robots. However, the electrostatic film motors have suffered from a technical issue caused by insulating liquid. To generate large force, the actuator must be immersed in insulating liquid. Lower viscosity has been preferred for the liquid, but such liquid can more easily volatilize and causes maintenance problems. To utilize highly-viscous liquid with lower volatility, this paper investigates how highly-viscous liquid affects the thrust force performance. Three silicone oils with different viscosities, as well as one insulating liquid (Fluorinert FC-770 (3M)), were compared in several different conditions. From our analysis, although high viscosity can degrades the force performance due to drag, the results suggested that the highly-viscous oil in the gap was moved by electrostatic force, and thus the viscosity does not always degrade the thrust force. It was also confirmed that in some particular conditions, the use of highly-viscous oil can even enhance the thrust force. On the other hand, highly-viscous oil degrades the backdrivability of the actuator while it is at rest, meaning that there is a trade-off between the force enhancement, volatility, and backdrivability.

Electrostatic motors are promising forms of actuation for future robotic devices. The study of their different implementations should accelerate their adoption. Current models for resonant electrostatic induction motors were found not to be able to properly describe their behavior, namely, with regard to changes with position. This paper reports a new analytical model for these motors, aiming to address this issue. The model is based on identification of all capacitance harmonics, through a simplified method. Using these, equations for different motor parameters, notably, thrust force, were obtained and compared to previous literature. The new equations model position dependent properties, such as force ripple. The outputs of this model were validated through experimentation with a prototype, with the results confirming the new model better describes motor behavior. An analysis into how to decrease this ripple was also discussed and tested. We concluded that the use of a higher number of harmonics resulted in a much more accurate model, capable of adequately characterizing motor outputs with changes in position.

The stability of the tunnel face is a top priority in a tunnel construction. The estimation of the earth pressure acting in front of the face is essential for the stability evaluation of the face, and many model experiments have been conducted to understand the characteristics of face stability. On the other hand, there are many cases in which the stability of the tunnel face is evaluated by limiting analysis assuming a constant slip region by applying the loosening earth pressure derived by Terzaghi as a boundary condition, but the actual slip region is not always constant and expanded progressively accompanying by the collapse of the face. There are few past studies that have considered this phenomenon. In this study, a estimation method of the tunnel face pressure are developed in consideration of the progress of face collapse. The proposed method is a kind of limit equilibrium method. Assuming a slip line with two ellipses with the same center and different radii, the first-order linear differential equation of earth pressure in the tunnel face direction is calculated from the equilibrium for infinitesimal elements in the circumferential direction.

High groundwater flow velocity is a major challenge in many artificial ground freezing (AGF) projects, especially in groundwater control projects. That condition may be unfavorable for the ...

In recent years, the number of cases where tunnels are constructed in sedimentary rock layers has increased. It is essential to investigate the deformation characteristics of sedimentary rocks for predicting tunnel deformation. The mechanical properties of sedimentary rocks are widely varied due to moisture content. The rocks are dried by tunnel excavation and wetted by groundwater gushing or backfilling. It is necessary to grasp the changes of deformation characteristics of sedimentary rocks due to moisture changes. In this study, soaking tests were conducted on Neogene period Japanese tuff sampled at Utsunomiya, Japan. In the test, the cylindrical tuff specimens are air dried by over 240 hours at first. Then the tuff specimens are taken in pure water with measuring deformations in detail. There are no effective stress increases by soaking and only uniform matric suction are acted on the specimen without any restraints. The results demonstrated that strain tensor was reached to stable state for 2 - 3 days, and the value of the normal strain perpendicular to the bedding plane is greater than the other normal components and shear strains are also observed in both cases. Although the orientation of the maximum principal strain is in the near of the bedding orientation at the initial dry state, the orientation are suddenly rotated to the normal orientation of the bedding plane. It means that the principal orientation of anisotropy are rotated due to continuous moisture changes.

Although it is essential for tunnel construction to evaluate the deformation behavior of sedimentary rock due to drying, the reasons for differences in the mechanical properties between dry and wet rock have not yet been clarified. A previous study on Neogene-period anisotropic tuff states that the magnitude correlation of the stiffness in the bedding orientation and its perpendicular one are reversed in the dry and wet states. Although this indicates the rotation of the principal orientation of the anisotropy, the mechanism is unclear. This phenomenon can clarify the stiffness differences between the dry and wet conditions if the deformation characteristics due to drying can be continuously obtained, in detail. In this study, drying tests on Japanese tuff are conducted, and the deformation behavior due to continuous moisture-content variation involving isotropic matric suction are investigated, in detail. The results of two specimens sampled in the bedding orientation and its perpendicular one show anisotropic deformations due to moisture variation. Normal strain in the orientation perpendicular to the bedding plane is dominant and shear strain occurs. Furthermore, principal strain rotation due to moisture variation is detected for the first time. The maximum and minimum principal strain orientations are rotated by approximately 90° from the wet state to dry state. It is determined that the hardest and softest orientations of tuff continuously alternate due to moisture variation.

Applying robots in narrow and cluttered disaster environments such as oil refineries requires a slim body and a wide range of motion. It is also necessary to have abilities to absorb unexpected contact with the environment and to walk on scattered debris. In this paper we propose new compact and high performance torque-controlled actuators for legged robots to satisfy the above mentioned requirements. For axial compactness, torque sensors are designed as ring-shaped thin cylinders surrounding motors or gears with strain gauges for sensing. To achieve broad bandwidth of torque control, we introduced an analog differentiator circuit into an analog digital converter (ADC) board in order to suppress noise in the differential control of joint torque. We also propose methods to reduce torque ripple caused by the deformation of the harmonic drive gear and electromagnetic interference (EMI) from a motor and a motor driver. Finally, experiments of a collision with objects and movement on scattered debris were executed with a fully torque-controlled legged robot built with the proposed actuators.

The authors introduce an experimental method that focuses on the flow-thermal relation and the visual observation of heat distribution around a cooling pipe in sand under the flow condition. This experiment aims to understand the effect of seepage flow on the heat transfer behavior of sand under cooling and freezing conditions due to a vertically buried heat exchanger pipe. This method combines a flow test, cooling or freezing processes, and the visual observations of temperature profiles with saturated Toyoura sand as the heat transfer medium. A vertical copper pipe inserted into the sand medium is used as the thermal exchanger, while an infrared thermograph is used to measure and visualize the surface-temperature profile of the specimen. The heat transfer distribution behavior is investigated by conducting a series of cooling and freezing experiments on the specimens with variation of the flow rate condition, initial condition, and pipe depth. The thermograph observation results show how water f...

Predicting the local size of a historic high-energy event from its boulders using numerical models is a challenging research topic. Modern high-energy events and their deposits are useful to validate these models; however, validating the accuracy of the results is difficult due to the scarcity of good datasets or the ambiguity of existing field data. Data on boulders transported by the 2011 Great East Japan tsunami at coastal sites (Settai, Taro, and Karakuwa) on the northeast coast of Japan were compiled. Pre-tsunami locations and settings and transport distances were found from evidence such as photographs, aerial images, and the testimony of survivors. The estimated weight of the boulders analyzed ranged from 11 to as much as 167 t, while the transport distance varied from a few to up to 600 m. Modeling results predicted that the minimum limit of maximum flow velocity of the tsunami at the pre-tsunami locations of the boulders varied from 4.2 to 6.8 m/s. The measured maximum flow depths at Settai (17–18 m) and Taro (14 m) were within the predicted range of flow depth when the Froude number = 1.0–1.5. Numerical model estimates for an older boulder (285 t) in Settai indicate that it was probably transported by a historical tsunami (1611 Keicho Sanriku event?) which may have been similar to or bigger than that of the 2011 event in the area. The maximum flow velocity could not have been less than 6.1 m/s, and if the boulder was transported to the present location by rolling, the flow velocity must have been within 7.5–23.7 m/s. Following systematic validation, the numerical modeling of boulder transport is proving promising for reconstructing the local magnitude of historical, high-energy events. Further improvements can be made with additional high quality field data from modern high-energy events.

In recent years, human-like robots have received a lot of attentions. A musculoskeletal humanoid is an effective approach for making a human-like robot, and many musculoskeletal humanoids have been developed. However, none have been equipped with really human-like bones and muscles, especially shapes and alignments. Formaking really human-like musculoskeletal humanoids, we thought of the “planar muscle” as the key. A planar muscle is an enhanced wiredriven system in which a motor winds a wire. In a prior system, one motor controlled one wire and the linear muscle needed one motor per wire and complex control systems. We therefore developed the planar muscle that controlled several wires simultaneously by using two moving pulley bars and one motor. The planar muscle is suited to musculoskeletal humanoids because they need a lot of motors and complex control systems in the case of using linear muscles. Furthermore, planar muscles are useful for soft skin-like outers that protect external shocks and sense touch. Using the planar muscles, we are developing a new musculoskeletal humanoid that has human-like bones and muscles. In this paper, we show the planarmuscle concept, especially its soft skin-like outer functions, and evaluate its motion with a body trunk model having multiple vertebrae that we developed.

This paper describes the petrological features and the ages of rock fractures filled mainly with carbonates at coastal outcrops of Yakushima Island, Japan. Microscopic observation and geochemical analysis were used to investigate the petrological features and the compositions of the fracture fillings. In addition, AMS 14C dating was also performed to estimate the ages of them. Microscopic study indicated that the fracture fillings contain not only cementing materials but also lithic fragments from host rock and bioclasts. SEM observation showed that the cements exhibit the characteristic textures of beachrocks. The cements were identified as Mg-calcite from XRD analysis. It was also observed from geochemical analysis that there were at least two stages of precipitation within the fractures. In addition, AMS 14C dating for seventeen samples of fracture fillings showed that the ages range from 2,460 to 5,130 years BP which is found to be younger than that of the uplifted coral at Yakushima Island (approximately 5,300–5,600 years BP). The results suggest that the fractures were solidified after the coral was uplifted.

Drying-induced deformations of porous materials are ubiquitous phenomena, but coupled behaviors of moisture content inside the material and deformation, which are difficult to express the behavior as a physical model. This is partly because multiple mechanisms governing drying-induced deformation are involved so that each mechanism may become dominant by respective situations. This article introduces various activities or efforts in some research fields, and retrieves common results in laboratory experiments and in field observations, mainly for sedimentary rocks. Through these processes, future works to be considered are elucidated.

In this study, an attempt has been made to investigate the deformation behaviour of Shirahama sandstone in drying process using small cylindrical samples. A series of comprehensive laboratory experiments was performed in different drying conditions under a no applied load. Saturated cylindrical samples were dried in a climatic chamber while deformation and evaporative water loss were being monitored. The results obtained are reported and further used in linear poroelastic relation in order to derive the matric suction evolution. In addition, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used for evaluating their pore structure and explained its role on measured strain and estimated matric suction. The results show that virtually no volume change occurs in the samples until half of the saturated water content is evaporated. It also reveals that the maximum dimensional change capacity is independent of drying condition but evaporation rate and strain occurrences are shown to be affected significantly. In addition, the study of pore structure indicates that substantial strain magnitude and high matric suction occurrence are attributed to water loss from small pores in the clay matrix. Throughout the process, the samples displayed neither a likelihood nor tendency of damage or destruction. However, strain magnitude is observed to be higher for the sample saturated with concentrated sodium sulphate solution. The present study sheds light on essential elements in the studies of dimensional changes of clay bearing sandstone to assist in evaluating ground movement, deterioration, fluid flow and isolation properties of underground facilities.