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Development of efficient lithium-sulfur (Li-S) battery requires the need to develop an appropriate functional separator that allows strong facilitation and transport of lithium ions together with limited passage of polysulfides. In this work, a multifunctional separator (TB-BAA/SWCNT/PP) is developed through spin coating of a novel zwitterionic microporous polymer (TB-BAA) on the gutter layer constructed from single-walled carbon nanotubes (SWCNT), where commercially available polypropylene (PP) separator is used to act as the mechanical support. SWCNT in this study serves as the first modification layer to decrease the size of the macropores in the PP separator, while the ultrathin TB-BAA top barrier layer with the presence of zwitterionic side chains allows the creation of confined ionic channels with both lithiophilic and sulfophilic groups. Due to the presence of available chemical interactions with lithium polysulfides, selective ion transport can be foreseen through such separator. In this regard, shuttle effect that is frequently encountered in Li-S battery can be suppressed effectively via implementing the as-obtained functional separator, resulting in the creation of credible and stable sulfur electrochemistry. The TB-BAA/SWCNT/PP-based Li-S battery has been investigated to possess high cycling ability (capacity fading per cycle of 0.055% over 500 cycles at 1 C) together with decent rate capability (736.6 mAh g

The shuttle effect and slow redox kinetics of sulfur cathode are the most significant technical challenges to the practical application of lithium-sulfur (Li-S) battery. Herein, a novel zwitterionic covalent organic framework (ZW-COF) wrapped onto carbon nanotubes (CNTs), labeled as ZW-COF@CNT, is developed by a reversible condensation reaction of 1,3,5-benzenetricarboxaldehyde (BTA) and 3,8-diamino-6-phenylphenanthridine (DPPD) with CNTs as a template and a subsequently-one-step post-synthetic grafting reaction with 1,3-propanesultone. The experimental results showed that, after loading active material sulfur, zwitterionic ZW-COF@CNT can effectively suppress the shuttle effect of the soluble lithium polysulfides (LiPSs) in Li-S batteries, and exhibits better cycling behavior than the as-developed neutral COF@CNT. Specifically, the as-obtained ZW-COF@CNT based sulfur cathode can maintain a discharge capacity of 944 mAh/g after 100 cycles, while that of COF@CNT based sulfur cathode drops to (665 mAh/g) after 100 cycles. Moreover, the ZW-COF@CNT based sulfur cathode delivers an attractive prolonged cycling behavior with a low capacity decay rate of 0.046 % per cycle at 1 C. This work sheds new light on rational selection and design of functionalized COFs based sulfur cathode in the Li-S battery.

Breaking waves interaction with two tandem cylinders are numerically studied using Computational Fluid Dynamic (CFD) software OpenFOAM. The effects of transverse inclined angles of the downstream cylinder and separation distances between two cylinders on breaking wave loads and free surface elevations are investigated. The interface between air and water phases is captured by the Volume of Fluid (VOF) method. The Shear Stress Transport k − v(SST k − v) turbulence model is employed to solve the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations. The present numerical model is validated against published experimental data by examining the horizontal breaking wave loads and free surface elevations of breaking waves past a vertical cylinder and an inclined cylinder. In the present incident wave conditions, the breaking wave force on the downstream cylinder decreases first and then increases with the transverse inclined angle varying from 0o to 30o, while it shows an opposite trend versus the distance between cylinders. The maximum breaking wave load on the downstream cylinder occurs when the it is installed vertically with a separation distance of four times diameter.

In this paper, seakeeping performance of vessels is comparatively investigated by means of improved 2.5D theoretical calculation, small-scale model towing tank test and large-scale free running model sea trial. This study also provides a scheme of ship vertical motion stabilization technique by using Semi-Submerged Bow (SSB) appendages. Firstly, an improved strip theory based 2.5D theoretical seakeeping algorithm, which considers the viscous flow effects attributed to bow appendages, is developed to estimate ship vertical motion responses in regular waves. Short-term predictions are also made on the basis of spectral analysis theory to predict ship motion responses in irregular waves. Then corresponding small-scale models are made and tested in a laboratory towing tank for both regular and irregular wave conditions to confirm the numerical results. The tank testing results between different ship schemes are also compared to experimentally investigate the effects of SSB and fin on hull vertical motion stabilization. Furthermore, large-scale model sea trials are conducted in coastal waves for a final validation of the ship seakeeping performance in short-crested sea waves. Finally, comparisons of the results by different testing approaches are systematically made and analyzed.

The novel testing technique for ship seakeeping behavior, which includes conducting large-scale model trial in realistic sea waves, has been given special attention by naval architects in recent years. Large-scale model measurement provides obvious advantages in the investigation of ship hydrodynamics in many aspects. However, there still exist some challenges that need addressing to improve this kind of testing technique. One of the great challenges is the reproduction of full-scale ocean waves when conducting downscaled model experiments in natural sea environment. This paper aims to explore the possibility of reproduction of full-scale wave states in coastal sea areas. Criteria, such as significant wave height, mean period, spectral shape and directional spreading, are involved in the wave similarity judgment. Various factors including season, climate, model scaling, coastal space and time are taken into account to determine suitable waves for model measurement. The wave selection principle and methodology proposed in this paper are demonstrated through a case study using coastal wave data of the Puerto Rico & Virgin Islands and the Gulf of Maine.

To overcome the loss of soluble lithium polysulfides (LiPSs) generated during the discharge process of lithium-sulfur (Li-S) batteries, a lot of efforts have been devoted to the design of novel micro- or nano-structured host materials, aiming to trap soluble polysulfide within the network. Covalent organic framework (COF) as porous materials have been receiving a great deal of attention. Herein, an allyl-rich triazine covalent organic framework (ART-COF) synthesized by 5-(allyloxy) isophthalaldehyde and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (TAPT) is used as cathode host material for Li-S batteries. Owning to the synergistic effect of physical force (through microporous channel) and chemical force (through C-S covalent bond and dipole–dipole interaction between nitrogen and lithium), the shuttle action of LiPSs to anode electrode can be effectively limited. ART-COF shows a high initial specific capacity of 1270 mAh g−1 which retains 1220 mAh g−1 after 100 charge–discharge cycles at 0.2C, and even at 1C it also demonstrates an initial specific capacity of 993 mAh g−1 which retains 818 mAh g−1 after 500 cycles with a low fading rate of 0.035% per cycle. This work represents a sustainable approach for developing highly stable and long-lived Li-S batteries.

The tumblehome hull adopts some novelty designs such as low-tumblehome freeboard and wave-piercing bow. The new form design makes the ship have many special hydrodynamic performances. Especially the green water of tumblehome hull is different from that of hulls with flare free board. Green water is a strong nonlinear phenomenon of ship-wave interaction, the variation of free surface of liquid is complicated, and there are still some difficulties to solve green water problems well with numerical simulation method. In this paper firstly the motion responses of the tumblehome hull was calculated based on 3D potential theory, and then the dam-break flow model was used to calculate green water height and pressure distribution. According to the result of numerical simulation, some typical working conditions are chosen for 3D CFD simulation using RANS method. The results of numerical simulation methods are compared with the experimental results measured in towing tank. The influence of different ship form parameters and wave parameters to the green water of tumblehome hull is analyzed, and some regularities of green water on tumblehome hull in regular waves are summarized.

During water exit of a solid body, the free surface is disturbed and deformed. To study the free-surface deformation and its dynamic change such as breakup, a set of water-exit equipment was designed and a series of experiment on water exit of a sphere were conducted. High-speed photographic technologies were adopted to capture the whole process of water exit and the large deformation of the free surface. Work was divided into forced water exit and free water exit. In the forced water exit, either a fully-submerged or a partially-submerged sphere was pushed out of water at a constant speed. The influence of the velocity or Froude number was investigated. In the free water exit, an initially static sphere with an equivalent density smaller than water was released underwater by using an electromagnet. Water exit at different initial submergence depth was conducted. Velocity and acceleration of the light sphere are analysed.

The calm water resistance of the models a bare tumblehome hull and with 3 different bow appendages (triangle fins, rectangular foil, and semi-submerged body) are predicted based on RANS and k-ε turbulence model using STAR CCM+ software. VOF method is used for the 2-phases simulation. The resistance calculation results of the bare hull are validated against model test data. The verification and convergence studies are carried out on the grid size and time step. The validation studies show that the relative changes of the resistance calculation results compared with the model test data for Fr = 0.294 are 5–6%. The results of resistance prediction for the hulls with 3 bow appendages show that the bow fin configuration shows the best performance at Fr = 0.220, and the semi-submerged body configuration shows the best performance at Fr = 0.367. The details of flow field of different hulls will be analysed in this paper.

Taking advantage of coastal wave environment to carry out scaled ship model test is an effective testing technology for ship performance. In this paper, the method of spectral analysis is adopted to calculate the significant wave height, period, wave spectrum and some other parameters of some places along the North Sea area of China. The measured wave spectrum and the ocean spectrum are handled into non-dimensional form to evaluate their similarity. The influence of wind direction and tide on coastal waves was analyzed. And the results indicate that the coastal wave spectrum is similar to the ocean spectrum under some specific conditions.

The development of large scale model measurements for ship hydrodynamic tests in natural environment in China is presented in this paper. Previous works of testing large scale monoblock models for seakeeping performance performed by Harbin Engineering University (HEU) are reviewed at first. To verify whether it is acceptable to perform tests near the shore instead of in deep-ocean, coastal waves were measured at different locations in the Bohai Sea and the Yellow Sea of China, and were compared with theoretical spectra. Then, a description of large scale model set-up, testing equipments, and experimental procedure regarding the segmented self-propelled model project is introduced and some typical results obtained from a recent sea trial are presented. Moreover, testing results by a corresponding small scale model in a laboratory basin as well as numerical results are compared with the large scale model experimental results to validate that the proposed testing method is reliable. Finally an overview of the ongoing large scale model laboratory plan and its future development directions is prospected.

The traditional laboratory models for the hydroelasticity and seakeeping performance of ships are tested in calm water and in uni-directional, artificially generated waves. A new alternative to the tank model measurement methodology is to conduct experiments using large-scale models in actual sea conditions. To implement the tests, a large-scale segmented self-propelling model and testing system were designed and assembled. A buoy wave meter was adopted to record the coastal waves that the model encountered during the tests. The analysis of the results of waves in sheltered waters by the spectral method shows good agreement with ISSC spectra. To investigate the difference between this new methodology and the traditional towing tank tests, a small-scale model, whose type and configuration are the same as those of the large-scale model ship, was used and tests were conducted in a towing tank. Comparison of the two experimental results shows that there is a remarkable difference in the response characteristics between the large-scale model at sea and the small-scale model in the tank. Numerical simulations of the responses of the ship under equivalent sea states were also carried out. The influence of directional spreading functions on the results was analyzed by a numerical approach. The classical model tests under long-crested waves in the towing tank over-estimate the motion and wave load responses; however, large-scale model tests carried out at sea are more reasonable for ship design and scientific research.

In order to accurately predict wave induced motion and load responses of ships, a new experimental methodology is proposed. The new method includes conducting tests with large-scale models under natural environment conditions. The testing technique for large-scale model measurement proposed is quite applicable and general to a wide range of standard hydrodynamics experiments in naval architecture. In this study, a large-scale segmented self-propelling model allowed for investigating seakeeping performance and wave load behaviour as well as the testing systems were designed and experiments performed. A 2-hour voyage trial of the large-scale model aimed to perform a series of simulation exercises was carried out at Huludao harbour in October 2014. During the voyage, onboard systems, operated by crew, were used to measure and record the sea waves and the model responses. The post-voyage analysis of the measurements, both of the sea waves and the model’s responses, were made to predict the ship’s motion and load responses of short-term under the corresponding sea state. Furthermore, numerical analysis of short-term prediction was made by an in-house code and the result was compared with the experiment data. The long-term extreme prediction of motions and loads was also carried out based on the numerical results of short-term prediction.

Although the nonlinear effects of the ship motions, wave-induced loads and structural responses of conventional vessels have been investigated experimentally and numerically in recent years, similar studies on the wave-piercing tumblehome (WPTH) vessels are rare, in spite of the urgent necessary due to their extensive applications. This paper experimentally investigated the nonlinear effects of the vertical motions and vertical bending moment (VBM) for a WPTH vessel based on a hydro-elastic segmented model test. The model test was carried out in head regular waves for three amplitudes, in the towing tank at Harbin Engineering University. Based on the band-pass filter technique, four kinds of decomposed harmonics are defined by mean offset, linear wave-frequency response, nonlinear wave-frequency response and nonlinear high-frequency vibration. Meanwhile, based on mean offset, three kinds of combined responses are defined by considering linear wave-frequency response, nonlinear wave-frequency response and nonlinear high-frequency vibrations step by step. The transfer functions of vertical motions and VBM are presented as function of the incident wave frequency, and the measured data and VBM were compared with numerical calculations for validation. With the method proposed above, the results of VBM are analyzed by focusing on the influences of decomposed harmonics on the amplitudes and asymmetry of combined responses. Strong nonlinear effects are observed in the VBM. The nonlinearity of VBM can be identified by the significant amplitudes of decomposed harmonics, variation of amplitude with the wave amplitude and remarkable asymmetry about the zero axis. The hogging VBM of WPTH vessel can be even larger than the sagging VBM, which is in contrast to the general experiences from conventional vessels. Combined the calculated relative motion with the decomposed and combined histories of VBM, the occurrence of the transient impact and its characteristics are discussed, and these are then used to analyze the unconventional asymmetry of VBM. Furthermore, the influences of the bow shape over the vertical motions and VBM are discussed. At the end of the paper, the uncertainties in the test are provided.

The hydrodynamic characteristics of a hybrid deep-V monohull with different built-up appendages are investigated experimentally in order to improve the resistance and seakeeping performance. Model tests have been carried out to study the hydrodynamic performance between a bare deep-V vessel and a deep-V monohull with different built-up appendage configurations (i.e. a hybrid deep-V monohull). From the model test results, it is found that the existence of the appendages will reduce the amplitude of pitching angle and bow vertical acceleration compared to that of the bare deep-V vessel in heading regular waves. However, the resistances for the hybrid deep-V monohull with built-up appendages are increased 15.6% for Fn = 0.264, and 0.1% for Fn = 0.441 compared to the resistance of the bare deep-V vessel. The model test results of seakeeping performance in irregular waves show that the hybrid deep-V monohull gives a better seakeeping performance than the deep-V vessel. The pitching angle and bow vertical acceleration of the hybrid deep-V monohull containing a built-up appendage are reduced 15.3% and 20.6% compared to the deep-V monohull in irregular waves at Fn = 0.441 in 6th class sea state (H1/3 = 6m).

Sun, S.; Qi, C., and Zhao, X., 2015. Investigation of turbulence models for hydrodynamics calculation and flow field analysis of hybrid monohull. The installing of semi-submerged body under the bow can improve the longitudinal motion performance of the ship effectively, and the viscous damping generated by the semi-submerged body has great effect of reducing rocking. Considering the viscous damping, the hydrodynamic coefficients of the hull were calculated by means of RANS method in this paper. The hydrodynamic coefficients were calculated by 3-D method respectively and the influence of different turbulence models on the calculation results for hydrodynamic was discussed. The result was analyzed and compared with the one calculated by means of source/dipole mixed-distribution method. Besides, the calculation efficiency for the different meshing methods and turbulence models of the three dimensional RANS method was discussed. It was confirmed in this paper that the RANS method is applicable to obt...

This paper presents the results of an experimental investigation of green water loads on a wave-piercing tumblehome ship. A water tank experiment was carried out in head regular waves by using a self-propelling segmented ship model. Wave probes and pressure sensors were arranged on the bow deck along the longitudinal and transverse directions. The height of water and the impact pressure on the deck were measured and their distributions in different wave conditions studied. The motion of the water flowing on the deck was recorded by a high-speed video system. Based on the experimental results, it was found that the green water is more serious with the increase of incident wave height and ship speed. The bow shape has little effects on the occurrence of green water, but it influences the green water loads to some extent. The distribution of green water pressure is different from that of green water height due to the strong nonlinearity of green water pressure.

The effects of the grafting densities (σp), molecular weights (Mn) and thicknesses of dry polystyrene (PS) brushes on their glass transition temperature (T) were investigated by ellipsometry. The results show that T strongly depends on the grafting density of the PS brushes. The T of the PS brushes with σp > 0.30 increases with decreasing Mn (or brush thickness) and is mainly dominated by entropic effects, in which the grafted chains are highly extended along the film thickness direction resulting in a sharp reduction in configurational entropy. The T of PS brushes with σp < 0.30 decreases with decreasing Mn (or brush thickness) which is mainly dominated by surface effects. For intermediate-density brushes (σp = 0.30), T becomes independent of Mn or brush thickness. The reason for this grafting density dependence of T is attributed to the transition of the PS brush conformation from mushroom-to-brush.

To elucidate the mechanism underlying the effect of polymer/solid interfacial interactions on the dynamics of thin polymer films, the glass transition of thin end-functionalized polystyrene films supported on SiO2-Si, such as proton-terminated PS (PS-H), α,ω-dicarboxy-terminated PS (PS-COOH), and α,ω-dihydroxyl-terminated PS (PS-OH), was investigated. All the PS films exhibited a substantial depression in Tg with decreasing film thickness, while the extent of such depression was strongly dependent on the chemical structure of the end groups and molecular weights. It was found that T - T of the various PS films increased linearly with increasing hads/Rg, in which hads is the thickness of the interfacial adsorbed layer and Rg is the radius of gyration of PS. The hads/Rg is a direct reflection of the macromolecular chain conformation within the adsorbed layer which was affected by its end groups and molecular weights. These findings are in line with the work of Napolitano, and present direct experimental evidence.

Crystallization is an important property of polymeric materials. In conventional viewpoint, the transformation of disordered chains into crystals is usually a spatially homogeneous process (i.e., it occurs simultaneously throughout the sample), that is, the crystallization rate at each local position within the sample is almost the same. Here, we show that crystallization of ultra-thin poly(ethylene terephthalate) (PET) films can occur in the heterogeneous way, exhibiting a stepwise crystallization process. We found that the layered distribution of glass transition dynamics of thin film modifies the corresponding crystallization behavior, giving rise to the layered distribution of the crystallization kinetics of PET films, with an 11-nm-thick surface layer having faster crystallization rate and the underlying layer showing bulk-like behavior. The layered distribution in crystallization kinetics results in a particular stepwise crystallization behavior during heating the sample, with the two cold-crystallization temperatures separated by up to 20 K. Meanwhile, interfacial interaction is crucial for the occurrence of the heterogeneous crystallization, as the thin film crystallizes simultaneously if the interfacial interaction is relatively strong. We anticipate that this mechanism of stepwise crystallization of thin polymeric films will allow new insight into the chain organization in confined environments and permit independent manipulation of localized properties of nanomaterials.

The seakeeping performance of trimaran is crucial to its design and development. A series of trimaran model tests for seakeeping performance are conducted in towing tank. Directional spectrum theory and long-crested wave theory are introduced to the spectrum analysis method so as to analyze the motion response of trimaran. The comparison of the results gaining from two theories and those achieving from the long-crested irregular wave tests is carried out. By statistical analysis, there is a big difference between the motion responses of trimaran according to different wave theories in several operating conditions. The characteristics of trimaran motion responses under different course angles are studied. Compared with long-crested wave theory, directional spectrum theory is introduced as a more accurate approach to research the seakeeping performance of trimaran.

The integrated sailing performance is important to the ship design and manufacture. However, it is very hard to be evaluated objectively and reasonably. In this paper the evaluation system of integrated sailing performance of ship’s was built which included seakeeping performance, wave loads, speed and stability performance in waves. The main characters were picked out and considering the influence of wave environment to build the evaluation system. AHP method was used to get the weight factors, and then the evaluation system could be built. So, the effects of wave and wind could be considered in the evaluation system. And then the evaluation system would be better than the single performance evaluation system and the evaluation system in calm water. The research of this paper is important to the integrated sailing performance evaluation system and evaluating method, which laid the foundation for the next step in the establishment of the comprehensive navigation performance evaluation equation for the ships in the waves. Keywordsintegrated sailing performance of ship’s; wave ; evaluation system; index; AHP method

Hybrid monohull is a kind of special monohull with a built-up appendage on the bottom of the bow. The appendage can produce a large damping force (moment) which conclude obviously viscous damping to greatly upgrade the ship's longitudinal motion performance. In this paper, the RANS method is used on calculating the hydrodynamic coefficients of different ships with and without the built-up appendage. By comparing with the calculating results using potential theory the viscous effect of the appendage is obvious. The longitudinal motion and wave loads of the two ships are predicted. The calculating results of the two ships are compared with each other to analyze the importance of viscous effect for the hybrid monohull. The calculating results are also compared with the model test results to validate the precision of the predicting method.