Characteristics of a bubble jet near a vertical wall

A numerical model of a coupled bubble jet and wall was built on the assumption of potential flow and calculated by the boundary integral method. A three-dimensional computing program was then developed. Starting with the basic phenomenon of the interaction between a bubble and a wall, the dynamics of bubbles near rigid walls were studied systematically with the program. Calculated results agreed well with experimental results. The relationship between the Bjerknes effect of a wall and characteristic parameters was then studied and the calculated results of various cases were compared and discussed with the Blake criterion based on the Kelvin-impulse theory. Our analyses show that the angle of the jet＇s direction and the pressure on the rigid wall have a close relationship with collapse force and the bubble＇s characteristic parameters. From this, the application range of Blake criterion can be determined. This paper aims to provide a basis for future research on the dynamics of bubbles near a wall.     

The asymptotic field of a dynamically growing crack in a viscoelastic materia

A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase,elastic deformation and viscous deformation are equally dominant in the near-tip field,and stress and strain have the same singularity,namely,(σ,ε ) ∝ r?1 /( n?1) . The asymptotic solution of separating variables of stress,stain and displacement in the crack-tip field was obtained by asymptotic analysis,and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation,it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M . When n →∞,the asymptotic solution of a viscoelastic material can be degenerated into that of Freund's elastic-ideally plastic material by analyzing basic equations.     

China has become a powerful port country

Open policy makes an influx offoreign capital in port investment Open policy on port investment, portsystem reform and a series of importantmeasures including the National Strategyon Coastal Port Development and the De-velopment Programme on Port Construc…     

Freight market prospects: a Baltic perspective

The indices of shipping freight market activity published daily by the Baltic Exchange, provide a graphic illustration of the vicissitudes of the international shipping industry and a useful reminder (if it were needed) of the basic economic principles of supply and demand.     

Design optimization of a torpedo shell structure

An optimized methodology to design a more robust torpedo shell is proposed. The method has taken into account reliability requirements and controllable and uncontrollable factors such as geometry, load, material properties, manufacturing processes, installation, etc. as well as human and environmental factors. The result is a more realistic shell design. Our reliability optimization design model was developed based on sensitivity analysis. Details of the design model are given in this paper. An example of a torpedo shell design based on this model is given and demonstrates that the method produces designs that are more effective and reliable than traditional torpedo shell designs. This method can be used for other torpedo system designs.     

Analysis of a marine cargo insurance case

Background: In a marine cargo insurance case, many glass lens was loaded in one container and transported from USA to Shanghai At the time of discharging, all pallets were found in normal condition. When the end-user received the cargo, one pallet was found fresh-waterdamaged. The glass lens were very carefully packaged and the warehouse was found dry and clean at the time of survey. It was assumed in the preliminary survey report that the water might have entered into the container through     

A well-functioning portis a stimulus for economy

Untiljustafewyearsago,portsinEuropehadaratherwishy-washyimage.Intheeyesofboththepublicandpoliticians,portswereanecessaryfactoflife.TheupsurgeoftheChineseeconomyandglobalisationingeneralhavechangedthis.Peoplehaveagainbecomeawarethatportsarethelifebloodoftheworldeconomy.InmanycountriesofWesternEurope,theyareagainrealisingthatawell-functioningportisastimulusfortheeconomy.IntheNetherlands,thepositiverevaluationevenledtoStateparticipationinthePortofRotterdamAuthority.Thishasbeenapubliclimitedl…     

Design and implementation of a visual monitoring system to ensure safety in the water surrounding a container vessel

Container vessels navigate among the world's ports,frequently passing through narrow and congested waters.Due to the many layers of containers on a container vessel's decks,it is difficult for the crew to be aware of all fishing vessels and other obstacles in a container vessel's radar observation blind zone.This greatly increases the risk of collisions and other accidents.Given such great challenges to safe navigation and safety management with container vessels,their security risks are severe.An effective visual monitoring system can improve the safety of the water area surrounding container vessel by eliminating a vessel's observation blind zone,providing an effective safety measure for vessels navigating fishing zones and other troublesome areas.The system has other functions,such as accident recording,ship security,and monitoring of loading and unloading operations,thus ensuring the ship operates safely.Six months'trial operation showed that the system facilitates safe navigation of container vessels.     

Forecasting short-term freight rate cycles: do we have a more appropriate method than a normal distribution?

General economists, as well as Maritime economists, assume that the time series they forecast follow normal distribution, and data is independently and identically distributed around the mean. This paper contests this assumption with the aid of three sets of time series: (1) The Dry Cargo Freight Index, 1741–2005: in this series the data deviate from the mean by more than three standard deviations on no fewer than six occasions, and exhibited “fat tails”; (2) The time charter freight rates for a 10-year-old, 80?000 dwt vessel from 6 January 1989 to 26 December 2008: this series also exhibits skewness and kurtosis in a leptokurtic distribution; and (3) The Dry Cargo Time Charter Index from 1971 to 2004: this series diverged from the normal distribution four times. Next, we searched more recent data for short-term cycles using the V-statistic. One cycle was found to last 4 years (2005 to 2008), which is in accordance with theory. This cycle started on 29 July 2005 and ended when it reached the (lowest) level of $4000 on 1 December 2008. A new 4-year cycle started on 1 December 2008 and is forecast to last until the end of 2010. Short-term forecasting of the cycle using V-statistic is theoretically confirmed by the theory advanced by Hampton [1990, published in 1989, ‘Analysis and shipping cycles I and II’, Seatrade Journal, 19–23. Long and Short Shipping Cycles: The Rhythms and Psychology of Shipping Markets, Monograph, 2nd ed. (Cambridge: Cambridge Academy of Transport), March, p. 66].     

Italian ports: towards a new governance?

The adoption in 1994 of the law n. 84 introducing the landlord port model marked the starting point of a prime period for the Italian port industry. It contributed to the national port industry renaissance: Italian ports became again the leaders in the Mediterranean basin, both as gateway ports and as transhipment ports. Looking back to its 15 years of enforcement, critical aspects and weaknesses have been observed. The incentive to reflect on the governance structure of ports and on the changes affecting the whole logistics transport chain is driven by the relative and absolute loss of position of Italian ports with respect to their competitors of the North as well as of the South European range (and the ports of Northern Africa which are expected to compete fiercely in the coming future). Considering only the container traffic, from 2003 to 2008 the market share of Italian ports decreased from 20.7% to 15.7% in favor of its main European competitors. The loss of attractiveness of Italian harbors is a clear symptom of the several difficulties national ports face in dealing with the rapid changes affecting the port industry. This paper discusses the bill presented by the Italian Government concerning the ports governance reform.     

A well-functioning port is a stimulus for economy

Until just a few years ago, ports in Europe had a rather wishy-washy image. In the eyes of both the public and politicians, ports were a necessary fact of life.     

Turbine speed control system based on a fuzzy-PID

The flexibility demand of marine nuclear power plant is very high,the multiple parameters of the marine nuclear power plant with the once-through steam generator are strongly coupled,and the normal PID control of the turbine speed can't meet the control demand.This paper introduces a turbine speed Fuzzy-PID controller to coordinately control the steam pressure and thus realize the demand for quick tracking and steady state control over the turbine speed by using the Fuzzy control's quick dynamic response and PID control's steady state performance.The simulation shows the improvement of the response time and steady state performance of the control system.     

制冷剂R134a的特性与应用

讨论了ＣＦＣＳ替代物Ｒ１３４ａ的推出及其应用，分析了Ｒ１３４ａ的性能与缺点，指明了理想的制冷剂的研究方向。     

Study on J-integral with SENB specimensin a condenser material

A series of tests was performed with three-point single-edge-notched-bend (SENB) specimens in a condenser material (Titanium alloy). Results show that the J-integral values of welded joint and HAZ are obviously smaller than those of the base metal. It signifies that the welding process can result in a reduced toughness of Titanium alloy and the effect of crack orientation on toughness value is not negligible for engineering applications. Besides, the J-integral values of L-T direction specimens are much higher than those of LS ones. The J-integral values of rolled ring are: J_(C-R)>J_(C-L)>J_(L-R).     

Research on stability design of a bar-reinforced spherical bulkhead

In this paper, the stability of a concave spherical stem bulkhead under the pumping load when still lying at the slipway is analyzed. The stability of the spherical stem bulkhead with different shell thickness and reinforcing forms is discussed. According to the results of stability analysis, the optimization design of the spherical stem bulkhead stability is performed. On the basis of considering the machining technical requirements of the bulkhead, a rational design of the spherical stem bulkhead structure is obtained. This paper has a certain value to the design of submarine's spherical stem bulkhead.     

珠江上游红水河断航36a后即将复航

本刊从广西港航局获悉，珠江上游红水河断航36a后，即将迎来复航。这意味着中国西南水运出海中线通道龙滩电站以下将全线贯通，成为连通粤、桂、黔三地的重要纽带。1975年，广西大化水电站开工建设，由于当时水电站未同步建过船设施，红水河断航。红水河因为长期停航，成为西南水运出海的”瓶颈”。2010年6月17日，西南水运出海通道工程（曹渡河口至桥巩段）宣告开工，并被列为自治区层面统筹推进的重大项目。     

Chinese shipbuilding growing from a sheep to an elephant

Increasing capacity scares others In mid-late1990s, China overtook Germany for the first time be- coming the 3rd largest shipbuilding country in the world. Though domestic industry sources were proud of this change, China was also confronted with differen…     

Numerical Simulation of Liquid Sloshing——a Review

Liqui dsloshing is associated with various engineering problems．Many studies have been performed since 1950s．A comprehensive review on the study and advance of numerical simulation of liquid sloshing．with emphasis on free surface tracking techniques，has been presented in this paper．At present．several methods can be used to simulate liquid sloshing numerically．However，each method has its own advantages and disadvantages and it should be applied according tO characteristics of practical engineering problems．In the future．further work should be placed on developing more effective techniques for treating very large amplitude sloshing problems，namely，for simulating overturning，breaking and merging of free surface，for predicting transient impact loads pressure of sloshing．     

使用R134a的离心式冷冻机的研制

IHI公司研制了使用R14a制冷剂的离心式冷冻机。这种制冷剂不存在损害臭氧层的问题,有望为下一代冷冻机所选用。该冷冻机主要特性是:采用高性能离心压缩机和热交换器(蒸发器和冷凝器),可达到节能化;为使用R134a,用高性能润滑油可提供相溶性和化学稳定性;新型电动机绝缘具有抗R134a和新润滑油溶解的性能。     

Dynamic Simulation of a Smart Crank and Slider Mechanism

In this paper, a smart crank and slider mechanism is analyzed mostly from a dynamic view. By means of dynamic explicit finite element method, 3D nonlinear structure is simulated. It is proved that the mechanism can effectively accomplish smart movement prescribed. And in order to ensure reciprocal movement with higher frequency, measures should be taken to avoid over heating of parts. Compared with internal energy, kinetic energy of total rigid body is dominating, and Y direction equivalent rigid velocity is much higher than X direction velocity. Equivalent rigid velocity of all parts is consistent with respective movement condition. For both energy and velocity, slider effect is dominating. Three direction equivalent inertia force oscillates. Force amplitude in Y -direction is comparitively the greatest.