Floating Body Research Articles

Numerical and Experimental Characterization of Rotational Floating Body Drag

Hydrodynamic drag plays a significant role in the motions and response of floating bodies – whether it be a wave energy converter, floating wind structure, or offshore oil & gas platform. Existing literature provides significant overview of the methodologies (both experimental and numerical) to characterize translational drag, however, there is limited research on the contributions (and methods of application) for rotational drag.
 
 This paper will detail both numerical modelling and a physical experimental campaign to assess how rotational drag impacts floating body dynamics, and best practices for numerical model inclusion. Specific focus will be on 1) the variety of methods used to input rotational drag into numerical models; 2) processes and lessons learnt from the experimental derivation of rotational drag coefficients; and 3) how does weakly non-linear wave stretching methods influence rotational drag.
 
 The experimental campaign is currently underway to classify the significance of rotational drag coefficients in characterizing floating body behavior. Translational and rotational drag coefficients of a simplified, inertial property matched, 1:50 floating body is being determined through a series of calibration tests. Both traditional free decay tests and forced oscillation tests will be implemented to evaluate these coefficients across multiple degrees-of-freedom. The final paper will present an overview of the experimental campaign, the results and lesson learnt.
 
 On the numerical side, the floating body will be modelled in the open-source wave energy converter modelling tool, WEC-Sim, and validated against the experimental results. Numerical results will be presented to review general body responses, with and without rotational drag, and generic wave conditions plus those expected at the PacWave wave energy test site in Oregon, USA.
 
 The inclusion of rotational drag coefficients and weakly nonlinear hydrodynamics are expected to improve computational model results, especially in the nonlinear wave excitation range, providing a better understanding of floating body behavior.

Method for Increasing Stability by Reducing the Motion of a Lightweight Floating Body

Method for Increasing Stability by Reducing the Motion of a Lightweight Floating Body

Design impact on three gate Dynamic Flash Memory (3G_DFM) for long hole retention time and robust disturbance shield

TCAD simulation using Silvaco software has shown that the 3G_DFM, which has SG1 (Select Gate 1), PL (Plate Line Gate), and SG2 (Select Gate 2) between SL (Source Line) and BL (Bit Line), has a long retention time of 100ms at 85 °C, and a robust disturbance shield which is a thousand times BL stress. The two select gates SG1 and SG2 protect the recombination of holes in the FB (Floating Body) at the SL and BL pn-junctions, and shield the BL stress arising during other page operations, which leads to the GIDL (Gate Induced Drain Leakage) current.

Area-efficient radiation-hardened 6 T SOI SRAM cell design using TDBC Transistors

Single event upset (SEU) is a critical issue for the static random access memory (SRAM) exposed to irradiated environments. In this paper, an area-efficient 6 T SRAM cell design based on partially depleted silicon-on-insulator (PDSOI) technology is proposed to improve the ability to resist SEU using tunnel-diode body-contact (TDBC) transistors. The proposed cell and 6 T floating body (FB) SOI SRAM cell are fabricated using 130 nm PDSOI technology for comparison purposes. Pulsed laser experiments show that, at the nominal supply voltage of 1.2 V, the energy threshold of the proposed cell increases by 25.2 % compared to the 6 T FB SOI cell with a similar area. The energy threshold of the traditional T-gate body-contact (TB) cell is also compared with that of the proposed cell.

Research on Structural Response Characteristics of Trapezoidal Floating Body in Waves

Floating structures plays an important role in extending and developing ocean resources, and their response evaluation is a hot topic of global important research due to the large dimensions. With characteristics including small depth and large horizontal plane, it is easy to induce the hydro-elastic resonant responses due to total stiffness. In this paper, first, the model design is performed to satisfy hydro-elastic similarity. Then, the model test is carried out in a wave tank to measure the structural response of a trapezoidal floating body in a series of waves. Secondly, the 3D hydro-elastic computational platform HOMER is applied to calculate the stress response of a trapezoidal floating body in numerical waves. The model test results and numerical simulation results are analyzed and compared and the conclusions are drawn, which indicate that a numerical method is effective to predict the structural response characteristics of a trapezoidal floating body. Above all, it is found that the significant response of a floating model is generated in some cases. The methods and conclusions of this study are used to provide reference and guidance for structural design of a trapezoidal floating body.

Analysis of Abnormal GIDL Current Degradation Under Hot Carrier Stress in DSOI-MOSFETs

It is generally believed that the gate-induced drain leakage (GIDL) current would increase with the hot carrier stress (HCS) time. As more interface electron traps are generated near the drain side, it results in a steeper energy barrier that makes the band-to-band tunneling (BTBT) process much easier. In this work, however, an abnormal decrease of such leakage current was observed in double silicon on insulator MOSFET under floating body (FB) condition. Through systematic characterization on different devices and operation conditions, we find that this behavior can be explained by the activation of lateral parasitic bipolar transistor (PBT), and the subsequent reduction of its current gain after the stress cycle. This is further supported by the simulation results that the induced additional traps would lower the amplified current by increasing the electron recombination rate. Our findings would shed more light on the roles of interface traps played in the MOSFET reliability analysis.

A Floating-Body Transistor-Based Power Amplifier for Sub-6-GHz 5G Applications in SOI CMOS 130-nm Process

A floating-body transistor based two stages power amplifier (PA) with lateral NPN based bandgap voltage reference (BVR) is implemented in a 130 nm Silicon-On-Insulator (SOI) CMOS process for sub-6GHz 5G applications. Floating-body (FB) transistors instead of traditional body-contacted (BC) transistors have been adopted in driver stage and power stage amplifiers of the proposed PA. On-chip input and output transformer baluns (TB) are customized designed for this PA which can realize impedance matching. Split push-pull structure is adopted in both driver stage and power stage with inter-stage matching networks. Incorporating bonding wire multi-physics models into input and output matching and power gain temperature compensation, the proposed PA can achieve maximum 25.6 dB power gain, 22.2 dBm output power and 28% power added efficiency (PAE) at 1 dB compression point (OP-1dB). The 3 dB bandwidth of the proposed PA is from 4.3 GHz to 6.4 GHz and the core size is 0.59 mm2. When the proposed PA is used for IEEE 802.11ac application and measured at VHT80 MCS9 (80MHz, 256-QAM), it can achieve 21.4 dBm output power and 24.8% PAE at 5.5 GHz operating frequency with −36 dB error vector magnitude (EVM).

Multi-Tunnel Triboelectric Nanogenerator for Scavenging Mechanical Energy in Marine Floating Bodies

The ocean has an abundant reserve of wave energy, which is considered to be a clean, widely distributed and inexhaustible resource. Triboelectric nanogenerators (TENGs) have been regarded as a reliable technology for harvesting wave energy due to its robustness and efficiency in scavenging random mechanical energy. In this study, a wave energy harvesting multi-tunnel TENG (MT-TENG) has been proposed, which could be integrated easily with ocean buoys. The MT-TENG consists of polytetrafluoroethylene (PTFE) balls and a multi-tunnel frame, which could convert wave energy into electrical energy. The multi-tunnel design also avoids possible mutual obstruction of the PFTE balls during the movement. Compared with the flat type structure, the multi-tunnel structure could enhance output performance obviously. With an agitation frequency of 2 Hz and vibration amplitude of 130 mm, the MT-TENG has a peak power density of 8.3 W/m3, which is five times that of the flat type structure TENG. By integrating with a life buoy and floating pipe line, the MT-TENG could harvest wave energy to light LEDs continuously, which could provide a new solution for maritime rescue and night offshore oil delivery warning.

Computational Study on Rogue Wave and Its Application to a Floating Body

A rogue wave is a huge wave that is generated by wave energy focusing. Rogue waves can cause critical damage to ships and offshore platforms due to their great wave energy and unpredictability. In this paper, to generate a rogue wave, a bull’s-eye wave, which is a focusing of multi-directional waves, was simulated in a numerical wave tank. A multi-directional wave generating boundary was developed using OpenFOAM, which is an open-source computational fluid dynamics (CFD) library. The wave height and profile of the generated rogue wave were compared to those of the regular wave. In addition, the pressure and velocity contours of water particles and velocity vectors at the free surface of the rogue wave were studied, along with the kinematic and dynamic effects of the rogue wave on a floating body.

Numerical Investigation of the Motion Characteristics of Cylindrical Floating Body in Waves Using the Volume of Fluid Method

In this paper, a numerical hydrodynamic performance assessment of a full scale cylindrical floating body with different damping devices is presented. The motion characteristics of the full scale cylindrical floating body are investigated in regular and irregular wave conditions with different wave heights and periods. A numerical wave tank based on the two-phase Volume of Fluid (VOF) model was established. Approaches to the computational domain and overset-grids were investigated and were found to be suitable. Grid convergence was undertaken for the simulations. The numerical wave tank was performed to analyse the motion characteristics of the cylindrical floating body with arbitrary devices under different wave conditions by using the VOF method with an overset-grid technique. The motion characteristics of the cylindrical floating body with different damping devices were numerically investigated to provide more information on the effect of damping devices on the hydrodynamic performance. The conclusions of this paper give guidance in the motion characteristics and the damping device prototype design to be adopted under the specified wave conditions.

Adaptive multi-body yawing filter of wave driven robot with dynamic response amending

Wave driven robots (WDRs) are a new type of autonomous ocean observation platform driven by wave energy. This paper is concerned with the multi-body yawing filter problem of the WDR. The adaptive multi-body yawing filter (AMF) of WDR was presented by considering the driven principle of the yawing motions of the submerged glider (glider) and the float body (float). The linearized yawing response models of the glider and the float were derived. The adaptive amending method of the dynamic response coefficients (DRCs) of the glider and the float were proposed. On this basis, the AMF of WDR was developed within the extended Kalman filter (EKF) framework. The AMF method utilized input and output (I/O) data to extract model information and is independent of the accurate mechanism model of the system. Numerical simulations of step steering and continuous steering under nominal model and the model with parameter perturbation were performed. The sea trial was conducted and the filtering results of the actual sensor data by AMF, EKF and tracking differentiator (TD) were presented. The proposed AMF method was found to be with good performance in suppressing noise and tracking speed.

Two-Dimensional Numerical Modelling of a Moored Floating Body under Sloping Seabed Conditions

A coupled floating body-mooring line model is developed by combining a boundary element model for a two-dimensional floating body and a catenary mooring line model. The boundary element model is formulated in the time domain by a continuous Rankine source, and a reflection potential is introduced to account for the wave reflection due to sloping seabed. This newly developed model is validated by comparisons against available data. Then, dynamic response analyses are performed for the moored body in various seabed conditions. Compared with a flat seabed, a sloping seabed causes unsymmetrical mooring line configuration and generates noticeable effects in the motion responses of the floating body.

Investigation on junctionless floating body DRAMs including Trap Assisted Tunneling

Junctionless Transistors (JL) and One-Transistor (1T) DRAMs are concepts that come out in order to improve the scalability of logic and volatile memories, respectively. In some recent papers, Floating Body (FB) DRAMs (a class of 1T-DRAM) and JL transistors have been joined in order to propose a solution to overcome the scaling limit of the conventional 1T-1C DRAM cells. In this paper they are discussed in detail the physics of operation and the performances of FB-DRAM cells based on JL transistors including the effect of Trap-Assisted-Tunneling (TAT), neglected in most of previous works. As expected, TAT severely limits the retention time due to the large doping, in particular during HOLD operation. The discussion is supported by 2D device simulation on a double gate junctionless transistor including the effect of statistical variability induced by random dopant fluctuations, and the technology (bandgap, lifetime) scaling. It is found that the cell, at least at the nanoscale, can work only by independent gate operation, having maximum performance when the bottom gate works at the limit of the BBT bias region during READ, and that at a gate length as large as 100 nm and fin width of 10 nm the cell can sustain the high doping induced variability to a retention time in the order of 1 ms, while the use of materials with higher bandgap (~1.3 eV) than Silicon can improve the retention time to the order of 10 ms. However several concerns remain on their actual use related to the necessary bias level and to the impact of the actual technologies on the lifetime, which strongly affects TAT degradation.

Analysis of the Sensing Margin of Silicon and Poly-Si 1T-DRAM.

Recently, one-transistor dynamic random-access memory (1T-DRAM) cells having a polysilicon body (poly-Si 1T-DRAM) have attracted attention as candidates to replace conventional one-transistor one-capacitor dynamic random-access memory (1T-1C DRAM). Poly-Si 1T-DRAM enables the cost-effective implementation of a silicon-on-insulator (SOI) structure and a three-dimensional (3D) stacked architecture for increasing integration density. However, studies on the transient characteristics of poly-Si 1T-DRAM are still lacking. In this paper, with TCAD simulation, we examine the differences between the memory mechanisms in poly-Si and silicon body 1T-DRAM. A silicon 1T-DRAM cell’s data state is determined by the number of holes stored in a floating body (FB), while a poly-Si 1T-DRAM cell’s state depends on the number of electrons trapped in its grain boundary (GB). This means that a poly-Si 1T-DRAM can perform memory operations by using GB as a storage region in thin body devices with a small FB area.

Comparing the TID-induced RF performance degradation of floating body and body contacted 130 nm SOI NMOS transistors

Total-ionizing-dose irradiation-induced RF performance degradation is observed in the input-output (IO) and core transistors of a 130 nm SOI NMOS technology. Different MOS structures including Floating Body(FB), T-gate Body(TB) and Tunnel Diode Body Contact(TDBC) SOI structures, were fabricated in a fully-integrated 130 nm SOI process. The radiation-induced DC and RF response of these devices was investigated. The impact of different structures and the use of body contact at PDSOI on the RF TID behavior are discussed by comparing their results to ionizing radiation experiments.

New method of temperature and conductivity sensor calibration with improved efficiency for screening SBE41 CTD on Argo floats

The global ocean monitoring system would benefit from improvements in the efficiency of Conductivity, Temperature, and Depth Device (CTD) sensor screening. Here, we describe the development of a new screening system, J-Calibration, for use with the SBE41 CTD sensor on the Argo float (Sea Bird Scientific). This new system has crucial advantages over the traditional SBE-Calibration system. First, J-Calibration does not require removal of the CTD sensor unit from the Argo float body to operate in a laboratory. This feature enables technicians or operators to more efficiently check the Argo target accuracies (± 0.005 °C for temperature and ± 0.01 PSS-78 for salinity) and allows the manufacturer’s warranty to remain intact. This also allows for a more efficient basic screening system which maintains screening accuracy without the need for specialized technicians. J-Calibration reduces the screening time to 1/6th that of SBE-Calibration and does not require the preparation of large amounts of artificial seawater. J-Calibration uses 1/23rd of the volume of seawater compared to SBE-Calibration by examining calibration at only 1 temperature point (22 °C), whereas SBE-Calibration requires 7 points to achieve calibration. The J-Calibration system does require careful temperature control of the artificial seawater as it is critical to maintain a uniform water temperature throughout the experiments. To satisfy this, using a vinyl greenhouse and covering sensors with adiabatic materials and cooling packs are effective. In comparison with the accuracy and system stability of SBE-Calibration, we show that the J-Calibration system is non-inferior and therefore is suitable for use in laboratory screening prior to deployment. Based on these advantages, the J-Calibration system will make a strong contribution to the deployment of healthy Argo fleets and to the maintenance of uniform data in the global ocean.

Dynamics modeling and experiments of wave driven robot

Wave driven robots (WDRs) take ocean energies as the power sources and are often used for long-term monitoring of the marine environment. The unique multi-body joint structure and special operation mechanism of a WDR make the dynamics modeling problem unusual. The dynamic model of a WDR was put forward by taking the interconnection of forces and motions between the float body (float) and the submerged glider (glider) into account. Numerical simulation of longitudinal motion and the comparison between simulation and tank test of reciprocating steering motion of the "Ocean Rambler" WDR were carried out. The dynamic model proposed in this paper was consistent with the motion characteristics of "Ocean Rambler" WDR. Simulations of PID heading control demonstrated the unique control characteristics of the WDR, which proved the significance of the established dynamic model of the WDR in control algorithm design.

Comparison of the Total Dose Responses of Fully Depleted SOI nMOSFETs With Different Geometries for the Worst Case Bias Conditions

Fully depleted (FD) silicon-on-insulator (SOI) nMOSFETs fabricated using 0.2- $\mu \text{m}$ SOI technology with external body contact (EBC) and floating body (FB) structures are irradiated up to 500 krad(Si) using 60Co gamma rays under the transmission gate (TG) and OFF bias conditions, respectively. The threshold voltage shift of the back transistors due to radiation-induced charge trapping in the buried oxide (BOX) is used to characterize the total dose response of irradiated back transistors. The results indicate that, overall, the TG biased EBC transistors with various gate lengths are more sensitive to the total dose radiation than the OFF biased FB counterparts at low dose levels. Furthermore, for the shorter gate transistors with a supply voltage of 1.8 V, a relatively complex correlation exists between the total dose response and the gate length. In particular, the back transistor of the TG biased 0.20- $\mu \text{m}$ 1.8-V EBC transistor reveals smaller threshold voltage shifts than the OFF biased counterpart at approximately 500 krad(Si) because of the saturation of its threshold shift with increased doses, and a similar radiation response is observed for the TG biased 0.35- $\mu \text{m}$ EBC transistor with a supply voltage of 2.5 V. We found that the 2.5-V back transistors exhibited greater radiation hardness than the 1.8-V counterparts with the same bias configuration in most cases.

몰수체의 면적 변화에 따른 부유식 구조물의 상하운동 저감 효과에 대한 실험 연구

본 연구는 부유식 구조물의 운동저감을 위해 다양한 면적과 형상의 몰수체를 적용한 실험적 연구이다. 부유식 구조물의 상하 운동을 저감시키기 위해, 부유체에 평판 형태의 몰수체를 용수철로 연결하였다. 다양한 면적과 형상의 몰수체를 사용하였고, 세 종류의 연결 용수철 강성 조건을 적용하였다. 이에 따른 부유체와 몰수체의 상하 운동 응답 변화를 비교하였고, 부유체의 운동 저감 효과를 측정하였다. 계측된 결과들을 비교 분석하여 최적의 몰수체 및 연결 용수철 강성 조건을 산정하였다.

Dynamics modeling of an unmanned wave glider with flexible umbilical

Unmanned wave gliders (UWGs) are a new type of wave-powered unmanned marine vehicle for persistent ocean environmental monitoring. The present paper proposed the dynamic model of a UWG by considering the influences of the flexibility of the umbilical. The dynamic models of surface float body (float) and submerged glider (glider) with slack umbilical were first separately established, and subsequently, the dynamic model of the UWG was formulated when the umbilical was under tension. Furthermore, the judgment principle and the state transfer problem in the switching process were analyzed, and numerical simulations of longitudinal and rotary motions of the UWG were performed. The established dynamic model was found to be reasonable to reflect the dynamic characteristics of the UWG with flexible umbilical.