以海为媒,踏浪而行——海洋技术与航海技术专业之异同

“东临碣石,以观沧海.水何澹澹,山岛竦峙.树木丛生,百草丰茂.秋风萧瑟,洪波涌起.”这是古人对波澜壮阔、能纳百川之海的歌颂和赞美.西方的童话故事“海的女儿”也家喻户晓,美丽的人鱼公主在旭日初升之时化作海上的泡沫,凄婉动人.现如今,我们面对海洋,不再只是站在陆地上喟叹其深邃辽阔,也不是只能幻想海洋里可能生活着什么样的生物,而是可以利用先进的科学技术去了解海洋、探究海洋,一层一层揭开它的“神秘面纱”.

Modeling Rice rgMT as a Plant Metallothionein-Like Protein by the Distance Geometry and Homology Methods

Rice metallothionein-like protein (rgMT) shows characteristics of a three-section pattern composed of two highly conserved cysteine rich (CR) domains in the terminals and a spacer without cysteine (cys) residues in the center of the molecule. In this paper, the two CR domains and the spacer region were modeled by the distance geometry and homology methods separately. For the CR domains, twenty random models were generated for each cys combination based on the constraint conditions of CXC (C represents cys, X represents any amino acid other than cys), and CXXC motifs and a metal-sulfur chelating cluster. Four models for the N-terminal and two for C-terminal CR domain containing metal chelating structures formed by different combinations of cys were selected from 900 possible conformations. The GOR method was used to predict the secondary structure of the spacer region and its model was built by the homology method. After three parts of the protein were modeled, they were connected to form a three-dimensional structure model of rgMT. The whole conformation showed that rgMT could form two independent metal-sulfur chelating structures connected by a spacer peptide, without a structural or energy barrier for them to form two independent metal-chelating clusters just as mammalian metallothionein (MT) proteins. As all plant metallothionein-like (MT-L) proteins have the same primary structural characteristic, two CR domains connected by a spacer region, and many have the same cys arrangement pattern as rgMT, the three-dimensional structure model of rgMT will provide an important reference for the structural study of other plant MT-L proteins.

NEW APPROACH TO COPYRIGHT PROTECTION OF IMAGE AGAINST GEOMETRICAL ATTACKS

To protect the copyright of the image as well as the image quality, a kind of image zero-watermark method based on the Krawtchouk moment invariants and timestamp is proposed. A method is used to protect the image, in which features are drawn out from the image as the watermarking. The main steps of the method are presented. Firstly, some low-order moment invariants of the image are extracted. Secondly, the moment invariants and the key are registered to a fair third party to gain the timestamp. Finally, the timestamp can be used to prove who the real owner is. The processing method is simple, only with a few low-order moment invariants to be computed. Experimental results are obtained and compared with those of the method based on geometric moment invariants. Results show that the scheme can well withstand such geometrical attacks as rotating, scaling, cropping, combined attack, translating, removing lines, filtering, and JPEG lossy compression.

Geometry Modeling of Ship Hull Based on Non-uniform B-spline

In order to generate the three-dimensional (3-D) hull surface accurately and smoothly,a mixed method which is made up of non-uniform B-spline together with an iterative procedure was developed.By using the iterative method the data points on each section curve are calculated and the generalized waterlines and transverse section curves are determined.Then using the non-uniform B-spline expression,the control vertex net of the hull is calculated based on the generalized waterlines and section curves.A ship with tunnel stern was taken as test case.The numerical results prove that the proposed approach for geometry modeling of 3-D ship hull surface is accurate and effective.

CFD simulation of solids residence time distribution in a multi-compartment fluidized bed

The present work focuses on a numerical investigation of the solids residence time distribution(RTD) and the fluidized structure of a multi-compartment fluidized bed, in which the flow pattern is proved to be close to plug flow by using computational fluid dynamics(CFD) simulations. With the fluidizing gas velocity or the bed outlet height rising, the solids flow out of bed more quickly with a wider spread of residence time and a larger RTD variance(σ2). It is just the heterogeneous fluidized structure that being more prominent with the bed height increasing induces the widely non-uniform RTD. The division of the individual internal circulation into double ones improves the flow pattern to be close to plug flow.

Investment decision optimization for delayed product differentiation based on queuing theory

To balance inventory cost with diverse demand,an optimal investment decision on necessary process improvement for delayed product differentiation is studied. A two-stage flexible manufacturing system is modeled as a continuous time Markov chain. The first production stage manufactures semifinished products based on a make-to-stock policy. The second production stage customizes semi-finished products from the first production stage on a make-to-order policy. Various performance measures for this flexible manufacturing system are evaluated by using matrix geometric methods. An optimization model to determine the level of investment on process improvement that minimizes the manufacturer ’s total cost is established. The results show that,a higher investment level can reduce both the expected customer order fulfillment delay and the expected semi-finished products inventory. When the initial order penetration point is 0. 4,the manufacturer ’s total cost is reduced by 15. 89% through process investment. In addition, the optimal investment level increases with the increase in the unit time cost of customer order fulfillment delay,and decreases with the increase in the product value and the initial order penetration point.

SYNCHRONIZATION RECOVERY SCHEME IN WATERMARKING DETECTION

Most proposed digital watermarking algorithms are sensitive to geometric attacksbecause the synchronization information of watermark embedding and detection is destroyed. Inthis letter a novel synchronization recovery scheme based on image normalization is proposed. Thepresented scheme does not require the original image and can be applied to various watermarksystems. A wavelet-based watermarking scheme is proposed as an example and experimentalresults show that it is robust to geometric attacks.

Capacity Research in Cluster-Based Underwater Wireless Sensor Networks Based on Stochastic Geometry

Underwater wireless sensor networks(UWSNs) have attracted wide attention in recent years.The capacity research on it is still in the initial stage,lacking adequate performance evaluation for network construction.This paper will focus on this subject by theoretical analysis and simulation,aiming to provide some insights for the actual UWSNs construction.According to the structure features of cluster-based UWSNs and the propagation characteristics of underwater acoustic signal,with the combination of signal to interference plus noise ratio,we define some capacity performance metrics,such as outage probability and transmission capacity.Based on the theory of stochastic geometry,a network capacity analytical model used in the cluster-based UWSNs is presented.The simulation results verify the validity of the theoretical analysis,and the cause of error between theoretical and simulation results has also been clearly explained.

Geometry and Dynamic Forces along an Inclined Hydraulic Jump over a Rough Channel Bed

In this investigation, based on previous measurements, the geometry and dynamic forces along an inclined （angle φ, with 0^0 〈 qφ φ 8^0 ） hydraulic jump over a variation of rough and smooth channel beds, are examined and compared among them. The roughness is produced through transverse strips （of square cross section） covering the entire channel width and at various normal distributions along the channel. Froude numbers are varying up to 18.5 and conjugate depths＇ ratios up to 18.4. The water free surface profiles, the conjugate depths＇ ratios, the jumps＇ dimensionless lengths are examined and a prediction of exercised forces, in dimensionless terms, is also presented. The results and especially the latter force prediction may help the hydraulic and structural engineers when dealing with such hydraulic jumps.

Basic Research on Key Techniques Related to Urban 3D Pipe Network Modeling

A new geometric modeling approach is introduced in this paper.First the principle of modeling of 3D pipe network is discussed in detail.Then the procedures of implementing pipe network visualization and system functions are presented.Last,several efficient methods for speeding up display of graphics are introduced.The new geometric modeling approach offers to people a new way to solve 3D visualization of complex urban pipe network.

Influence of wave and current on deep-sea mining transporting system

As a solution to the breaking of pipeline under high axial force,carbon fiber composite pipe with low density and high intensity is applied to deep-sea mining transporting system.Based on the fact that the transporting pipe is under the forces of gravity,inner liquid,buoyancy as well as hydrodynamic force,geometric nonlinear finite element theory has been applied to analyzing the transporting system.Conclusions can be drawn as follows.Under the interaction of waves and currents,node forces FX and FZ acted by the transporting pipe on the mining vehicle are less than 2 kN,which indicates that waves and currents have little influence on the spatial shape of the transporting pipe and the mining vehicle movement.On the other hand,the horizontal force acting on the mining ship could be as large as 106 830 N,which has great influence on the mining system.

Madagascar High Lands Dry Season Forages： Lofium multiflorum （Italian Ray Grass） and Avena sativa （Oat）

Italian ray grass and oat are two grass species characterized by their ability to adjust tropical climate conditions. This study proposed to assess forage productivities to allow an appropriate mowing period determination in their use as dairy female feed in Madagascar. A test on small plots has been set up in the southern part of the capital city Antananarivo during one dry period （4 months）. Live observations followed by laboratory proximate analyses have been performed for forage productivity and feeding value determination. Cultivated on tanety （hill）, irrigated in counter season, results show that： （I） oat higher height （H = 96.7 cm） than Italian ray grass （H= 69.4 cm） at 99 days of age; （2） similar biomass productivity; （3） dry matter yields significantly different （p = 0.05）; （4） certain similarity between dry matter yields and FMU （fodder milk unit） score evolution; （5） leafy stage of Italian ray grasses at 99 days of age; （6） mid-flowering stage for oats during the same period. Cell wall content, crude fiber and dry matter contents increased with age （p = 0.05）. Crude proteins and minerals evolved in opposite directions. Gross energy content did not present precise variation with age. This study allowed that for an acceptable quantitative and qualitative production during dry seasons, good mowing period for Italian ray grass could start at 76 days age, while oat could start being harvested at 68 days.

Liquid holdup measurement with double helix capacitance sensor in horizontal oil-water two-phase flow pipes

This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.

A geometric Model for the Spatial Correlation of an Acoustic Vector Field in Surface-generated Noise

Spatial correlation of sound pressure and particle velocity of the surface noise in horizontally stratified media was demonstrated, with directional noise sources uniformly distributed on the ocean surface. In the evaluation of particle velocity, plane wave approximation was applied to each incident ray. Due to the equivalence of the sound source correlation property and its directivity, solutions for the spatial correlation of the field were transformed into the integration of the coherent function generated by a single directional source. As a typical horizontally stratified media, surface noise in a perfect waveguide was investigated. Correlation coefficients given by normal mode and geometric models show satisfactory agreement. Also, the normalized covariance between sound pressure and the vertical component of particle velocity is proportional to acoustic absorption coefficient, while that of the surface noise in semi-infinitely homogeneous space is zero.

Morphological Research on Geometrical Scattering Waves of an Underwater Target

In this paper, a new method based on morphologic research named reconstruction cross-component removal （RCCR） is developed to analyze geometrical scattering waves of an underwater target. Combining the origin of the cross-component in Wigner-ViUe distribution, the highlight model of target echoes and time-frequency features of linear frequency-modulated signal can remove cross-components produced by multiple component signals in Wigner-Ville distribution and recover the auto-components of output signals. This method is used in experimental data processing, which can strengthen the real geometric highlights, and restrain the cross components. It is demonstrated that this method is helpful to analyze the geometrical scattering waves, providing an effective solution to underwater target detection and recognition.

Shed Light on the Geometrical Configuration and Structural Principle of an Ancient Wooden Bridge in Qingming Shanghe Tu

In the centre of the famous Chinese painting, Qingrning Shanghe Tu, an arch-shaped timber bridge, Hongqiao, stands like a rainbow over the river Bianhe. Unfortunately, Hongqiao was damaged during floods from the Yellow River, and we can only see her beautiful form in Qingming Shanghe Tu. While, the geometrical dimensions, structural principle, as well as the construction methods of the bridge are still an interesting mystery. In the present paper, the author uncovers the structural principle and the geometric dimensions of the bridge as well as its history background. Furthermore, the author introduces two new structural systems, Lap-Beam and 1.5-Layer space frame, which are inspired by the structural principle of the Hongqiao.

Motion Geometric Active Contours: Tracking Nonrigid Objects in Clutter Background

MGAC (Motion Geometric Active Contours), a new variational framework of geometric active contours to track multiple nonrigid moving objects in the clutter background in image sequences is presented. This framework, incorporating with the motion edge information, consists of motion detection and tracking stages. At the motion detection stage, the motion edge map provides an approximate edge map of the moving objects. Then, a tracking stage, merely using the static edge information, is considered to improve the motion detection result. Force field regularization method is used to extend the capture range of the edge attraction force field in both stages. Experiments demonstrate that the proposed framework is valid for tracking multiple nonrigid objects in the clutter background.

Solute Transportin Sand Columns as Affected by Effluent Surface Tension

Transport of nonreactive solutes in soils is principally controlled by soil properties, such as particle-size distribution and pore geometry. Surface tension of soil water yields capillary forces that bind the water in the soil pores. Changes in soil water surface tension by contaminants may affect flow of soil water due to decreased capillary forces, caused by lowered soil water surface tension. This study aimed at assessing solute transport in sand columns as affected by effluent surface tension. Miscible displacement （MD） tests were conducted on sand columns repacked with sands sieved from 2.0, 1.0, 0.5 and 0.25 mm screens. The MD tests were conducted with 0.05 M bromide solutions prepared using water with surface tension adjusted to 72.8, 64, 53.5 and 42 dyne/cm2. Obtained breakthrough curves were modeled with the convection-dispersion equation （CDE） model. Coefficient of hydrodynamic dispersion and pore-water velocity responded inconsistently across decreased particle-sizes and water surface tensions and this was attributed to non-uniform effect of lowered effluent surface tension on solute transport in different pore-size distribution.

Study on the Water Surge Height Line of Landslide Surge of Linear River course Reservoir Based on FLOW-3D

The occurrence and transmission attenuation of surge is always a problem that researchers pay much attention to. The influence of the first wave height of landslide surge and the following transmission attenuation of surge are involved with many factors, which are mainly： landslide water entry angle, river course depth, river course geometrical properties and landslide mass and material, etc.. This thesis is mainly a research on the properties and transmission attenuation rules of landslide surge which is caused by linear narrow river course. Numerical value simulation will be applied in this thesis to discuss about the features and rules of the occurrence and transmission of surge in different landslide water entry angles and under different influences.

A multiple watermarks algorithm for image content authentication

A novel multiple watermarks cooperative authentication algorithm was presented for image contents authentication.This algorithm is able to extract multiple features from the image wavelet domain,which is based on that the t watermarks are generated.Moreover,a new watermark embedding method,using the space geometric model,was proposed,in order to effectively tackle with the mutual influences problem among t watermarks.Specifically,the incidental tampering location,the classification of intentional content tampering and the incidental modification can be achieved via mutual cooperation of the t watermarks.Both the theoretical analysis and simulations results validate the feasibility and efficacy of the proposed algorithm.