Search

Denial of service is becoming a growing concern. As computer systems communicate more and more with others that they know less and less, they become increasingly vulnerable to hostile intruders who may take advantage of the very protocols intended for the establishment and authentication of communication to tie up resources and disable servers. This paper shows how some principles that have already been used to make cryptographic protocols more resistant to denial of service by trading off the cost to defender against the cost to the attacker can be formalized based on a modification of the Gong-Syverson fail-stop model of cryptographic protocols, and indicates the ways in which existing cryptographic protocol analysis tools could be modified to operate within this formal framework. We also indicate how this framework could be extended to protocols that do not make use of strong authentication.

Plastic deformation, as a type of micro-damage caused by external loads such as earthquake, is necessary to be evaluated by using an efficient non-destructive evaluation technique in order to guarantee the structural safety. In this paper, the feasibility of the pulsed eddy current testing method for evaluating the plastic deformation in an austenitic stainless steel has been studied through experiments and simulations. Moreover, the electromagnetic property variations due toplastic deformation have also been investigated.

The recently proposed picture fuzzy set (PFS) is a powerful tool for handling fuzziness and uncertainty. PFS is character-ized by a positive membership degree, a neutral membership degree, and a negative membership degree, making it more suitable and useful than the intuitionistic fuzzy set (IFS) when dealing with multi-attribute decision making (MADM). The aim of this paper is to develop some aggregation operators for fusing picture fuzzy information. Considering the Muirhead mean (MM) is an aggregation technology which can consider the interrelationship among all aggregated ar-guments, we extend MM to picture fuzzy context and propose a family of picture fuzzy Muirhead mean operators. In addition, we investigate some properties and special cases of the proposed operators. Further, we develop a novel meth-od to MADM in which the attribute values take the form of picture fuzzy numbers (PFNs). Finally, a numerical example is provided to illustrate the validity of the proposed method.

Control of clamping pressure on blood vessel is a commonly concerned issue in minimally invasive surgeries. While complicated sensing-feedback-control systems are developed for clamping in robotic surgeries, a simple mechanism for the pressure control is desired. In this paper, we propose a new structure of endoscopic forceps to solve the problem of nonlinear relation between the clamping pressure and grasping force. A shape memory alloy (SMA) wire embedded endoscopic clamp is proposed to control the clamping pressure within a safe range. A typical configuration of the clamp is designed based on the discussion on the detailed geometric dimension of SMA wires and blood vessels.

In this paper results are presented of tests with models sailing in head waves at restricted water depths of 1.875, 2.5 and 3.75, 2.5 and 3.75 times the ship's draught. Also results given of calculated ship motions in deep water. No attention is paid to ship motions in shallow water. A discussion is given about the influences of the water depth on the ship motions. It is shown how the ship motions at restricted water depths can be determined from the ship motions in deep water.

In this paper a method is given for the assessment of cavitation inception, for the calculation of the type and extent of cavitation and for the calculation of the effect of cavitation on lift and drag. A boundary layer analysis of experimental results of cavitation studies on hydrofoils indicates that cavitation inception occurs in the laminar- transition region of the boundary layer. This fact is used to derive an approximate relation for the inception location and for the corresponding value of the cavitation number. Results of cavitation studies on hydrofoils are also used to derive a relation for the type and chordwise extent of cavitation and for the assessment of the influence of cavitation on lift and drag. The validity of these relations are demonstrated by comparing theoretical and experimental results for the case of marine propellers.

The paper discusses the casting, molding materials, machinability, and alloying materials in the manufacture of propellers. Included are the fatigue properties, fatigue strength with respect to corrosion, the effect of cavities and grain structure, fracture and the use of various materials for propellers. The final section deals with the strength of propellers, including loading, damage and blade stress variations under different wake conditions.

This paper deals with the effect of restricted waters on the added mass of rectangular cylinders moving in a free surface of rectangular channels, because the rectangular forms can be regarded a a representative of the main part of an actual ship. The moving directions of the cylinder are either parallel or perpendicular to the free surface. Moreover, the frequency of motion is either infinitesimal or infinite. That is, the former is concerned with the manoeuvring motion and the latter is concerned with the ship's hull vibration. The content of this paper overlaps a part of previous articles, but also includes new results obtained after those articles were completed.

This paper describes the second phase of a hybrid computer simulation of two ships maneuvering during underway replenishment operations. Two identical Mariner class merchant ships are used in this study. However, the simulation program is easily adapted to any class of surface ship. The ships' dynamics are simulated on an EAI 680 analog computer, while the nonlinear interaction forces are generated on a PDP 15 (DEC) digital computer. The first phase of the project considered only the interaction effects on the leading ship due to the close proximity of the tracking ship. This second phase considers the interaction effects on both the leading and tracking ships in calm water and in two different regular seas. Computer runs are made to study the control variables necessary for manual control of the leading and tracking ships. A third phase will be directed to establishing the essential variables needed for ship control during underway replenishment and their required accuracy. Selection and display of these manual control parameters for monitoring by the conning officer and/or helmsmen may extend the operating conditions under which underway replenishment can be carried out.

This paper deals with the problem of the prediction of the effective wake distribution in the propeller plane of a ship, using the measured nominal wake of a model as a starting point. The chosen prediction method consists of two successive steps. viz. a scale effect correction to obtain the nominal wake field of the actual ship and the prediction of the difference between nominal and effective wake. With regard to the scale effect, a method is introduced based on a threefold contraction of the model nominal wake field in dependency of its harmonic content. An empirical approach is used to account for the scale effect on the diffusion of the wake peak in the centerplane which starts as soon as the flow has left the stern. Further, the scale effect on bilge vortices, assuming that they are generated near the same point on ship and model, is calculated. Application of the method shows promising results. It is felt, however, that our knowledge of the scale effect on generation of bilge vortices is unsufficient at present. The need for more correlation data is emphasized. Concerning the transition from nominal to effective wake, a rough estimate is made of the influence of the propeller-hull interaction on the flow by a) an approximation of the influence of the image of the propeller in the hull, b) a concentric contraction of the wake field to account for changes in the boundary layer profile and c) the calculation of the effect of screw race contraction on the axial velocity distribution in the bilge vortex, if present.

Previous applications of regression analysis to ship data are reviewed and these reveal a lack of appreciation of the consequences of statistical theory. The paper therefore considers this theory and its influence on the choice of data and of independent variables, on the features and the accuracy of a good regression equation, and on the scope of proposed designs to which the equations can be applied. Examples of regression analysis of some hydro-static and resistance data are given which show that neat, consistent and accurate equations can be derived. Recommendations are given on the presentation of regression analysis results and it is concluded that the technique is ideally suited for developing empirical expressions for use as aids to ship design.

In this paper the open-water characteristics of the Wageningen B-series propellers are given in polynomials for use in preliminary ship design studies by means of a computer. These polynomials were obtained with the aid of a multiple regression analysis of the original open-water test data of the 120 propeller models comprising the B-series. All test data was corrected for Reynolds effects by means of an equivalent profile method developed by Lerbs. For this Reynolds number effect additional polynomials are given. Criteria are included to facilitate the choice of expanded blade area and blade thickness. Finally, a number of new type of diagrams are given with which the optimum diameter and optimum RPM can easily be determined.

This paper presents an attempt to establish scaling laws. The author restricts the problem to find the method of estimation from a model test to its prototype. So, the hydrodynamic similarities such as the cavitation number and the load distribution along a blade are assumed to be similar between the model and its prototype. Also the working fluid is assumed same in both cases. Then there is no scaling effect on the fluid property. The problem is reduced to how to estimate the depth of erosion of the prototype from that of model where the flow condition and the property of the material are known. First an empirical formula which is based on experiments will be proposed, then a more complicated analysis will be presented where a modeling of mechanism of cavitation erosion will be made.

None of the damage concepts in current use for estimating the fatigue life of a ship takes into consideration the complete history of the stress spectrum of that ship. The work presented in this paper is an attempt to establish a method that takes into consideration the whole spectrum in the estimation of the fatigue life of a ship. Discussions of the effects of corrosion allowances, stress concentrations, the ratio of hogging to sagging as well as the effect of load variation between ballast and full load conditions are also presented. The method is applied to predict the fatigue life in a number of practical cases.

The paper considers the problem of propeller noise aboard ships. It is proposed to describe a cavitating ship propeller as a source of sound in terms of the source strength of a monopole which is situated near the position of a propeller blade tip. A new method for the measurement of this source strength is presented. The method is based on the application of the reciprocity principle. The source description and the measurement method can also be applied in relation to the problem of propeller induced vibrations. The first experiences with the method are very promising.

This paper describes a new method for the three-dimensional (3-D) tracking and the quantification of blood vessels from Magnetic Resonance Angiography (MRA). The approach is based on the 3D geometrical moments and consists of the following steps : (1) interactive selection of 3-D seed points ; (2) automatic tracking of the vessels ; (3) local computation of both diameter and orientation ; (4) rendering of the vessels. This detection and estimation scheme has been validated on simulated and real data.

The paper describes a new hull form, intended to improve the efficiency of ships' propellers by so shaping the afterbody that it forms a stator. Model tests were carried out to compare a hull having the new afterbody form with a conventional twin-screw hull which had the same forebody, an identical midship section, and an afterbody whose curve of immersed transverse sectional areas was very close to that of the new form. These tests showed that in the design speed range a maximum saving on the propulsive power of 24% could be made by adopting on both models twin three-bladed screws of the same form, and of 26% with the same two-bladed propellers, leaving the way open for a further improvement towards a 30% saving. Several factors contribute to the overall saving, each having a comparable degree of influence. All the factors affecting propulsive power, namely the towing resistance, the thrust efficiency, the wake coefficient, the counter-propeller effect and the relative rotative efficiency of the propeller, play their part. The benefit from the improved rotative efficiency is connected with a marked reduction in the mechanical vibrations imposed on the hull by the working conditions of the propeller blades, which makes it possible to adopt two-bladed screws, and so to benefit from their better free water efficiency.

In the last years a number of papers related to the application of optimization methods and parametric studies in pre-contracted design have been published. The present paper makes a comparison of these two techniques, discussing their advantages and disadvantages. It proposes some means by which these techniques can be used more efficiently. They are later supported by an exact description of the sample programs for optimization and parametric study.

The improvement in performance which can be obatined by application of ducted propellers on bulk carriers and tankers depends very much on the afterbody-nozzle configuration. Investigations carried out so far on these applications are mostly restricted to isolated cases. In this paper, based on systematic tests performed in the Depressurized Towing Tank of the Netherlands Ship Model Basin, information is given about the influence of nozzle length, nozzle shape, propeller diameter, hull-nozzle clearance and about the influence of adaptation of the nozzle to the wake flow on the performance of large ships.

A great deal of effort has been devoted in recent years to study of the deformation of the wake from propeller blades. Relationships between loading, vortex rollup, contraction, and pitch variation have been studied. This paper discusses analytical and experimental developments, and emphasizes the effects on design and performance of high speed high thrust subcavitating propellers.

In this paper general account is given of the problems involved in the selection of specific values for the design parameters of marine propellers. The views and data presented are of a general nature and illustrate some of the choices involved in the design of a screw propeller such that the extent of cavitation is minimized or controlled.

Vessels operating in the offshore industry call for propulsion units with specific requirements on performance in widely varying conditions, noise production, speed of control, and other properties. In this paper experimental information is given on subjects for design and simulation purposes.

The effect of the number of free stream nuclei on marine propeller cavitation, type and extent, is investigated. It is found that an increase of free stream nuclei simulates cavitation inception and stabilizes the cavitation pattern. In this paper some preliminary results are presented.

This paper discusses an on-line computer experiment aimed at determining the unsteady lift characteristics of hydrofoil sections using multi-frequency disturbances and numerical processing based on fast Fourier transform techniques. The results achieved are compared with those obtained using a conventional Transfer Function Analyzer. The advantages of the former approach are the vastly reduced time required to perform the experiments and the very small input disturbances necessary to excite the system under test.

Strength calculations for propellers are usually made using nominal static load values with fluctuations due to circumferential wake field variations superimposed. The allowable load is then determined by applying experimentally obtained material properties (Smith/Goodman diagrams) on the computed stress pattern. Approval of the final calculations by the Classification Societies is contingent upon the strengthening of certain components to ensure a higher survival rate in off-design conditions. Poor engineering judgement in applying these heavy duty requirements can lead to constructions where strength levels at several critical points is badly harmonized. This can lead to severe damage to the propeller, shafting, gearbox or even the hull. The paper presents an analysis of two such cases resulting from grounding incidents. The requirements of Lloyd's Register, Germanischer Lloyd and Det norske Veritas for ice strengthening are compared with those of the Finnish- Swedish rules for the extreme ice class and shown to differ considerably. The Finnish-Swedish rules show a substantial increase in thickness of the blades for the lower power range, whereas the Lloyd's register percentage method results in a superfluous blade thickness for the high powers. A simplified analysis of the effects of underwater explosions on propeller and shafting is given and the paper concludes with examples of the calculation of stresses in complex shaped and loaded parts using modern numerical methods.

The paper presents a generalized discussion of the problems of determining power and speed from the results of model tests with special reference to scale effect. Correlation methods used in Kockum's yards are outlined with examples of their application to large tankers and ships. The trend towards larger ships has revealed some limitations of the method for computing full scale revolutions, and further research is considered necessary in this area. The paper concludes with a review of work on the measurement of wake field, cavitation and vibration.

A series of model experiments has been conducted with a stern trawler model, in which the main parameters governing the motion of a side launched vessel were systematically varied. The paper presents the results of the tests in the form of dimensionless equations to enable launching characteristics of similar vessels to be predicted in advance. Practical applications of the results are discussed.

In this paper a proposal is made for assessing the stopping ability of ships by use of a ship's own constant, called the ship's time constant. With the help of this constant it is possible to plot the results of stopping manoeuvers in a dimensionless form and the basic relations are more evident in the case of different influences. The magnitude of the ship's time constant differs very much between the different types of ships and it is shown in the paper that this constant determines the stopping ability of a ship. The dimension of the constant is that of a time in seconds for example and means the time period for losing 50% of the ship's speed measured from the instant when the energy input is cut off. Under these circumstances the time constant or half-value period of a ship also has a concise significance for nautical people.

Several characteristics of whipping vibration stress due to slamming impact in regular waves are referred to and the long-term predictions of whipping vibration and wave bending stresses are carried out for the large full ship of L = 247 m, C//B = 0.824. The whipping vibration stress is as large as the wave bending stress in rough seas. This paper clarifies that the reasonable determination of allowable stress or safety factor for the longitudinal strength of ship body must contain the transient whipping vibration and springing stresses. Some theoretically predicted results are compared with the experimental results and a fairly good agreement can be seen between them.

Many numerical methods--transfer matrix, finite difference and finite difference and finite element methods--which take piece-wise account of the variation of the input-datas over the length of the ship hull, such as area, weight, etc., are now available. Most of these methods give deflection and rotation as output in the eigenvalue problem or in the modal analysis, from which vibratory bending moments and shear forces for given exciting forces and moments are obtained after numerical differentiation of deflections and rotations of cross-sections. In order to avoid this numerical differentiation after the modal analysis, the force method can be employed, instead of the usual deformation method, for improved accuracy in ship hull vibration analysis. In this paper, the necessary differential equations of vibrations are derived and analogies between the force method and deformation method are established so that the existing programs in deformation quantities can be used. Moreover, the eigenfunctions of shear force and bending moment and the envelopes of their maximums for an impact force and moment under vertical vibrations are presented for an ice-going ship.

The paper presents a hydrodynamic model for the rudder action of a ship in shallow water, which is based on two ideas. 1) The ship-rudder system is considered as a slender wing, and the rudder acts as a trailing-edge flap. 2) The shallow-water effects can be modelled by "Newmans" theory for a slender body between two parallel walls. The resulting theoretical model leads to predictions for the sway force and yaw moment derivatives with respect to sideslip angle, yaw rate and rudder deflection in water of arbitrary but constant depth.

This paper deals with the problem of the behaviour of a ship in restricted waters with special regard to underkeel clearance. The main factors affecting the keel clearance are squat, heaving and pitching motions, the occurrence of a heeling angle due to wind pressure and rudder movements and the rolling motion. Distinction is made for canals, shallow water of finite width and shallow water of infinite width. It is emphasised that the efforts are mainly concentrated on the several calculation procedures which exist for squat and the difficulties involved in practical applications. With respect to the ship motions in shallow water waves a simple calculation method according to the conventional strip theory is presented and discussed.

This paper deals with the steady hydrodynamic problem of a single-rudder ship moving parallel to a vertical wall in shallow water. The ship-rudder system is considered as a wing with a flap. The main result of this theoretical study is that the sway force and yaw moment due to the presence of the wall ( "bank suction" ) can be cancelled by giving the rudder a suitable deflection towards the wall, at virtually zero yaw angle.

In this paper the Authors examine the nonlinear equations of ship rolling from a control engineering viewpoint by considering the ship as represented by a feedback system. This enables the describing function technique to be brought to bear on the problem. They discuss, in detail, the extension of this technique due to West and others which can account for so-called "frequency distortion of the spectrum" in nonlinear systems and point to evidence which appears to show this happening in practice. Accuracy estimates using describing function analysis are difficult to specify since they are affected by many difference factors, however they are commonly reckoned to be about 10% accurate with wideband excitation.

A review is given of the cavitation observation techniques as used in the NSMB Depressurized Towing Tank. Special attention is paid to those observation and recording techniques which are suitable for studying the time-dependent behaviour of propeller cavitation. The paper also includes the description of a method, based on stereo photogrammetry, to determine the topology of the cavity on a propeller blade.

After a brief survey of shallow water phenomena this paper presents some features of a new laboratory at SSPA in Gothenburg, designed with special attention to shallow water problems. The arrangement of height-adjusted wave flaps is discussed in the light of pre-design wave form experiments. In 1977, before the installation of the wave-generators and the wide-span multi-motion carriage, the basin was used for a variety of special studies of ship behaviour in shallow water, mostly by means of remotely controlled 5 m models. The description here includes some results of definite model trail maneuvres with the subsequent identification of hydrodynamic parameters, of the motion of a model past a short bank and a comparative simulation, of the additional squat experienced due to a local shallow, and of the wave-making of a model at near-to-critical speed.

This paper presents revised formulae for statistical power prediction based on a greater number of results than the original equations reported in a previous paper which comprised a numerical representation of resistance properties and propulsion factors that could be used for statistical ship performance prediction. Following over a year of experience, several fields for improvement of the derived prediction methods given before are indicated, namely: The formula for wavemaking resistance does not include the influence of the bulbous bow. The resistance of ships with large bulbous bows is overestimated by the original formula. The wavemaking resistance of ships with a large waterplane-area coefficient is overestimated by the previous formula. The accuracy of the formula for the thrust-deduction fraction for a slender single-screw ship appeared to be insufficient. The wake fraction and the model/ship correlation were not properly represented by the formula for full ships at ballast draught. Order from BSRA as No. 49,917.

In this paper a ship-rudder system is considered as a low-aspect-ratio wing with a hinged flap. The model is restricted to single-rudder ships in deep water. A lifting-surface theory is used to compute the lateral forces on the ship caused by a rudder deflection. Attention is paid to the influence of the rudder's length and height. The results are compared with those from slender-wing theory.

This paper presents an extensive investment--and replacement model especially designed for the shipping industry. The method is based on linear programming techniques, after a survey of existing methods the model developed at the Delft University of Technology is highlighted. Together with a verbal description of its constitution the formal representation of object function and constraints is given. The method has been applied to a fictitious examples, of which the results are presented. Order from NSFI as No. 17316.

In Switzerland a most progressive Federal Water Protection Law offers a sound basis for the realization of comprehensive and efficient water pollution control. Since the enforcement of this Law in 1972, great and meritorious efforts have been undertaken by Federal, Cantonal, and local authorities. Nevertheless, after a phase of tremendous progress, especially in the putting in to operation of sewage treatment plants, it seems necessary to reflect on the further development of water protection. In this paper concept and implementation of water protection in Switzerland are discussed and consequences for future policy suggested. The authors wish to emphasize that the views expressed here are intended to be of a critical nature. While showing existing deficiencies, we are fully aware of the fact that time may often be a limiting factor when aiming at the utilization of the legal potential. The ambitious legal water quality goals aimed at represent a great challenge to the Swiss authorities. The critical review presented here concerning water protection in Switzerland may — with respect to many aspects — be applied to the situation in many other countries, thus being of general validity.

The character of the ship structure and the loadings encountered in the design of ships poses a special problem of plate instability. A semianalytical method has been proposed in the paper to analyze the stability of ship plating and allied plated structures. The method is general and can be used to study the buckling of plates having any boundary and loading conditions, as well as for isotropic, orthotropic and variable thickness plates. It is simple and economic. Rectangular plates having different end conditions and loadings have been analyzed. Excellent accuracy has been obtained.

The Author, of National Cheng-Kung University, Taiwan, discusses theoretical investigations of wave-excited ship vibrations (springing) in regular waves and confused seas. For deterministic analysis, a step-by-step approach is linked with the transfer matrix technique for determining the springing response in regular waves. The main advantage of the transfer matrix technique is its systematic formulation, and one of the major features of the step-by-step approach is its generality. This approach can be used to tackle the sinusoidal or non-periodic vibration problems. Through the application of the present approach the effects on springing of vibratory deflection, ship motions, and the time rate of change of sectional added mass (dm'/dt) are also studied. For statistical analysis, the ship behaviour in confused seas has generally been predicted with "short-term" springing response in most of the existing information. This "short-term" value, which is obtained by combining the deterministic analysis results and wave spectra, cannot be the basis of ship design since it cannot predict the probabilistic maximum springing response over the ship's lifetime. For practical application, the "short-term" value needs to be extrapolated into the "long-term" value. This further step has been completed in the present paper. For a ship in regular waves, the influence on springing of the key parameters such as draught, ship speed, and heading angle is also examined, and the theoretical explanation for the trend of springing response to each influencing factor is presented.

The purpose of this paper, which is based on work done by CETENA is to assist the ship designer by presenting a method for expressing a merit rating characterising the seakeeping qualities of a proposed design, so enabling him to make an objective choice from alternative solutions at an initial design-stage. The rating is a mathematical factor based upon ship-speed, and indicates the percentage of its life that the ship will be fully operational from the seakeeping viewpoint. The method has been developed by (a) determining the phenomena that limit the ship's operability, and the maximum allowable intensity of each of these effects; (b) formulating a valid analytical expression for the long-term probability distribution of the sea conditions; (c) determining, on the basis of the geometrical characteristics of the hull, the maximum wave height beyond which the ship is no longer operational at a given speed; and (d) establishing, on the basis of the long-term probability distribution of sea conditions, the probability that this maximum wave height will be exceeded. These four steps are explained in detail, and the method is illustrated in an example in which three warships of different nationalities, having similar lengths and displacements, are compared from information on their body plans and overall weight distributions, the only essential elements for the application of the method. The comparison is made in respect of sea-state probability distributions in the areas: World-Wide, Northern North Atlantic, North Atlantic, and Mediterranean. Seven speeds, between zero and 30 knots, in head seas are considered in the comparison. It is concluded that it now seems possible to relate the operational efficiency limits of a ship to an overall merit rating expressed by the annual average speed which can be maintained in the geographical are under consideration, and that the comparison of hull designs on the basis of the seakeeping merit rating can be made independently of the geographical area (though the world-wide sea-state distribution might conventionally be used).

Organizations, in our view, are epistemological systems, bodies of knowledge which are the accumulation of past debates with regard to goals, purposes, and beliefs. Policies, plans and strategies are current dialogues intended to change that corpus of knowledge. Consequently, a theory of argumentation is a requisite paradign for studying organizations and for solving their problems. This paper explores this point of view. The question, “How can we uncover policy arguments and assess their structure, strengths and weaknesses?” is posed and, drawing on recent developments in logical theory, some preliminary answers are provided. In summary, we see stakeholders as the basic logical entities of organizations. Assumptions are made about the status and behavior of these entities and these assumptions are treated as claims in an argument. The support for a claim is provided by data and warrents which are either stated explicitly or derived through the logical process of retroduction. The resulting collection of claims, data and warrants generally contain inconsistencies which may, in turn, be studied by means of plausibility analysis. The paper develops a logic adequate to carry out this perspective and identifies a series of research questions. The outcome is a new approach to policy and planning.

This paper is an attempt to direct present-day research in programming language specification and their compiler construction towards a more natural approach. In order to do that, a language is considered for what it is, namely a communication device between systems. In view of this evidence, the first section of the paper develops a framework for the natural specification of language. Section two of the paper develops the HAS-Hierarchy as a device to be used in this natural language specification. Section three of the paper constructs a general model for programming language specification by the HAS-Hierarchy. Section four is devoted to the problem of compiler construction by using the HAS-Hierarchy as a natural tool for programming language specification.

Although instances of fatigue damage to bronze propellers have been steadily decreasing in recent years, the subject of propeller blade fatigue continues to be a matter of some interest. The authors, of Lips B.V., examine several aspects of blade fatigue and, with the aid of data from other studies, derive a simulation model for fatigue damage accumulation and the resulting propeller life expectation. The blades considered are of Ni-Al bronze. A case study is described in which the model is used. The paper is presented under the headings: 1. Introduction. 2. Hydrodynamics: Propeller Blade Loading (1--General. 2.-Ship's stern motions in a sea state. 3--Sea states. 4--Ship's resistance increase in a seaway. 5--Blade loading). 3. Materials Fatigue Behaviour (1--Ship and propeller particulars. 2--Selection of sailing route. 3--Relation between ship's speed and sea-state. 4--Propeller loading. 5--Load cycle determination. 6--Damage accumulation). 5. Discussion and Conclusions. It is concluded that: (i) In the case of a non-linear relationship between blade stress deviations and ship motion, a real-time simulation method can be used to assess the stress distribution during a given period. (ii) In the case studied, the results of which are thought to be representative of the class of ship concerned, only a narrow stress distribution resulted from ship motions; this additional contribution to damage accumulation is negligible. (iii) A design philosophy based on a safety factor related to nominal stress conditions seems to be the most rational for propeller design purposes; the safety factor incorporates allowances for defects, fatigue strength fluctuations in the material, and self-stresses.

Flexible manufacturing systems are highly customized, computer integrated machining systems with the potential for automating small batch production. So far research has concentrated on the solution of their technical problems; very little effort has been devoted to the organizational issues they raise. This paper discusses some initial findings from an ongoing in-depth case study of the organizational problems of flexible manufacturing systems in a division of a large corporation. Five implementation issues are stressed: transfer of technical knowledge, workgroup structure, quality control and maintenance, impacts on other parts of the organization, and the meaning of flexibility. Where possible, solutions are recommended for the problems raised.

Most managers become concerned with environmental issues only after they have become societal problems whose solutions are the subject of legislation. As a result of this time-lag between the emergence of the societal issue and its legislation, and the ensuing managerial response, most management is kept busy fighting past wars rather than planning strategies for the future. This paper provides a framework which allows the manager considerable leeway in the environmental issue emergence process, thereby enabling the organization to pro act and redesign its structure and behavior in anticipation of certain future events.

In preliminary design studies, it is frequently necessary to estimate the calm-water resistance characteristics of various hull forms prior to model tests. For such estimations, use is generally made of results of well-known methodical model experiments, such as Taylor's Standard Series, Series 60, and others, to determine the effect of specific hull-form parameters on resistance. For small high-speed displacement vessels designed to operate in the speed range corresponding to Froude number values of 0.4 to 1.1 (equivalent to a range in V/square root L of 1.34 to 3.70), these well-known methodical series results are inadequate due to the limited speed range covered and alternative methods must be used. This paper presents all available and reliable data for the prediction of the resistance of small high-speed vessels designed to operate in the displacement mode. Included are the results of restricted and less well-known methodical series and averaged results or tests with a large number of non-systematic models, in both graphical and numerical form. Some basic considerations on how and when each of the presented methods can be applied are also presented.

The Integrated Marine Propulsion System (IMPS) developed by I.H.I. is a special propulsion unit comprising a non-reversing medium-speed diesel engine combined with a single reduction gearbox incorporating the lubricating oil and cooling water pumps and the drives required for the main electric generator and a controllable pitch propeller. The advantage of this arrangement is that the CPP can be controlled directly from the bridge throughout the entire range of seagoing or manoeuvring conditions without overloading the engine or causing vibrations and overheating. The first IMPS units were developed to provide the I.H.I. Friendship and Freedom Mk II ship series with an economic propulsion system compatible with other features of these ships. This paper presents the design criteria of the system and describes the propeller requirements which have had to be taken into account in the development of the system. The results of tests and trials of the installation on board the first ship of the Friendship series are presented and discussed. Principal particulars of Friendship and Freedom Mk II ships are given in an Appendix to the paper.