Fuzzy expert system for controlling swamp terrain intelligent air-cushion tracked vehicle

A fuzzy expert system was used in this study to control an intelligent air-cushion tracked vehicle (IACTV) as it operated in a swamp peat terrain. The system was effective in controlling the intelligent air-cushion vehicle while measuring the vehicle traction (TE), motion resistance (MR), power consumption (PC), cushion clearance height (CCH) and cushion pressure (CP). An ultrasonic displacement sensor, pull-in solenoid electromagnetic switch, pressure-control sensor, microcontroller, and battery pH sensor were incorporated into the fuzzy expert system (FES) to experimentally determine the TE, MR, PC, CCH, and CP. In this study, we provide an illustration of how an FES might play an important role in the prediction of the power consumption of the vehicle’s intelligent air-cushion system. The mean relative error in the actual and predicted values from the FES model with respect to tractive effort, total motion resistance and total power consumption were found to be 5.58 %, 6.78 % and 10.63 %, respectively. For all parameters, the relative error in the predicted values was found to be less than the acceptable limit (10%), except for the total power consumption. Furthermore, the goodness of fit of the predicted values was found to be close to 1.0 as expected and, hence, indicates the good performance of the developed system.     

Seabirds utilizing the Northeast Water polynya

A small seabird community depends on the resources of the Northeast Water (NEW) polynya. In spring, at least 1000 King Eiders and 2500 Common Eiders form pre-breeding congregations at Ob Bank before dispersing in mid June to breeding areas. The most abundant species is the Fulmar, which breeds in six colonies with a total of 2550 “apparently occupied sites”, corresponding to approx. 1475 active pairs in 1993. Kittiwakes occupied almost 900 sites at Mallemukfjeld, with an estimated 733 breeding pairs. The entire NEW area probably holds 400–500 pairs of Ivory Gulls, and about 500 individuals were associated with a colony on Henrik Krøyer Holme; this is one of the world's largest known colonies. Sabine's Gulls breed at the same islands and on Kilen (approx. 50 pairs in each place). Small colonies (total less than 1000 birds) of Arctic Terns are distributed along the edge of the polynya, with the largest colony of about 100 pairs on Henrik Krøyer Holme. The Black Guillemot is the only breeding auk species (< 20 pairs) in the area. Small numbers of Red Phalaropes were observed in the polynya in 1992 and 1993, and the species may have bred at Henrik Krøyer Holme in 1993; the polynya area may also serve as a staging area for transpolar migrants. In late summer a few hundreds of Ross's Gull—non-breeding adults and immatures—show up in and around the polynya, and in recent years a few cases of breeding have also been recorded. The relatively small seabird populations are evidence of a generally low carrying capacity of the polynya area.Apart from the benthic foraging eiders and the Black Guillemot, the seabird community of NEW consists of surface feeders—Fulmars and gulls—dependent on small fish and zooplankton. During their stay in the NEW area, the five most abundant surface feeders will annually consume approximately 243,000 kg (wet weight) of food, of which the Fulmars alone take 67%. Food demand in relation to area of open water in the polynya is highest in spring (approx. 0.2 kg/km²), which is     

Linear Quadratic Gaussian Control of a Quarter-Car Suspension

This paper presents a method for designing linear multivariable controllers in the frequency-domain for an intelligent controlled suspension system for a quarter-car model. The design methodology uses singular value inequalities and optimal control theory. The vehicle system is augmented with additional dynamics in the form of an integrator to affect the loop shapes of the system. The measurements are assumed to be obtained in a noisy state, and the optimal control gain and the Kalman filter gain are derived using system dynamics and noise statistics. A combination of singular value analysis, eigenvalue analysis, time response, and power spectral densities of random response is used to describe the performance of the active suspension systems.     

Material transport from the nearshore to the basinal environment in the southern Baltic Sea: I. Processes and mass estimates

Processes involved in erosion, transport and deposition of cohesive materials are studied in a transect from shallow (16 m) to deep (47 m) water of the SW Baltic Sea. The wave- and current-induced energy input to the seabed in shallow water is high with strong variability and suspended matter concentrations may double within a few hours. Primary settling fluxes (from sedimentation traps) are less than 10 g m⁻² day⁻¹, whereas resuspension fluxes (evaluated from sedimentation flux gradients) are 15–20 times higher and the residence time for suspended matter in the water column is 1–2 days. Settling velocities of aggregates are on average six times higher than for individual particles resulting in an enhanced downward transport of organic matter. Wave-induced resuspension (four to six times per month) takes place with higher shear stresses on the bottom than current-induced resuspension (three to five times per month). The short residence time in the water column and the frequent resuspension events provide a fast operating benthic–pelagic coupling. Due to the high-energy input, the shallow water areas are nondepositional on time scales longer than 1–2 weeks. The sediment is sand partly covered by a thin fluff layer during low-energy periods. The presence of the fluff layer keeps the resuspension threshold very low (<0.023 N m⁻²) throughout the year. Evaluated from 3-D sediment transport modeling, transport from shallow to deep water is episodic. The net main directions are towards the Arkona Basin (5.5×10⁵ t per year) and the Bornholm Basin (3.7×10⁵ t per year). Energy input to the bottom in deep water is low and takes place much less frequently. Wave-induced resuspension occurs on average once per month. Residence time of particles (based on radioactive isotopes) in the water column is half a year and the sediment accumulation rate is 2.2 mm year⁻¹ in the Arkona Basin.     

Complexity theory applied to management of shipping companies

Theory of complexity , in the author's opinion, describes life better than the hitherto available theories, as it deals more effectively with dynamic, non-linear and cyclical phenomena. The author will here attempt the application of the theory of complexity to the management of shipping companies , especially those of Greek management style. This paper will also deal with the relationship of competition in shipping. The question that will be put and answered is whether a firm should be a hierarchical, inflexible structure, ordered from above. If, however, a company is seen as a self-organized emerging order, then a new approach must be adopted, i.e. that of complexity theory. The choice of the above combination is because a shipping environment is indeed unpredictable, volatile, cyclical and international, as well as complex. It is believed that this new theory can yield a new, more pragmatic, insight into the way shipping companies and ships should be managed. The innovative element of this work is that it will be the first time internationally (except for the work of Li and Parsons [1]) that the theory of complexity will be applied to shipping. In addition, no previous attempts have been made to apply this theory to management of shipping companies.     

Optimal design of an engine mount using an enhanced genetic algorithm with simplex method

This study provides an analysis of the applications of optimization routines for designing fluid mounts. After summarizing the concept of fluid mounts and their dynamic characteristics, we review the importance of the notch and resonance peak that occur in dynamic stiffness of fluid mounts. Fluid mounts are tuned for specific application so that their notch frequency coincides with the disturbance frequency, by selecting the proper parameters for the mount. Additionally, the mount parameters are selected such that the notch remains as deep (close to zero) as possible and the resonance peak is kept as short as possible. The notch depth and resonance peak present opposing requirements for the selection of mount parameters in the sense that lowering one will result in increasing the other. Using a bond graph model, this study will evaluate the effect of various parameters on the mount notch depth and resonance peak height characteristics. The results show that different parameters can have a varying effect on the notch frequency and depth, as well as the resonance frequency and peak height. The results of the study are extended by examining the effectiveness of two different optimization methods—namely, the Enhanced Genetic Algorithm (EGA) and Sequential Quadratic Programming (SQP)—for selecting the combination of parameters that can yield the deepest notch and shortest resonance peak. Using two different design cases, the study shows that SQP exhibits much more sensitivity to the initial conditions that are selected for the mount parameters than EGA. Both methods, however, are able to converge to an optimal solution within the constraints that are selected for the parameters. For both cases, EGA is able to converge to the set of parameters that provide a deep notch and a short resonance peak.     

Accurate INS position solution during GPS outages or degraded GPS

Temporary degraded GPS (DGPS) position loss, in circumstances such as an overhead bridge, can be alleviated by an inertial navigation system (INS) that uses onboard sensors, such as yaw and speed sensors, to determine vehicle position. This paper introduces a post-processing DGPS/INS integration approach based on using the INS solution during DGPS outages or periods of low accuracy DGPS position solutions. In this approach, the INS solution initialization is performed using the DGPS solution before DGPS position solution loss, and measurements from the Inertial Measurement Unit (IMU). The final post-processed INS solution is a weighted average of the INS forward and backward solutions. This work constitutes two parts: the INS initialization methods for different degrees of freedom vehicle positioning models, and the developed weighting model necessary to combine the forward and the backward solutions. The former part is essential in obtaining acceptable INS initial states for both the stand-alone INS or any post-processing or real time INS/GPS integrated system. The latter part is based on the use of the complementary error behaviours of the backward and the forward solutions, and can be used as a survey method with acceptable position solutions accuracies. Applying the forward/backward INS combined solution method on real data shows that the resultant INS solution accuracy is 35 cm or less over a 1000 m road segment. This method is used to survey freeways interchange road segments where 50% of the surveyed distance has no DGPS solution or has a degraded DGPS solution. The average achieved accuracy over the whole freeways interchange is around 40 cm over a 23 km distance.     

Late-Quaternary changes in productivity of the Southern Ocean

Paleoceanographic records based on new proxies of export production have been constructed for the South Atlantic sector of the Southern Ocean. A radionuclide-ratio proxy of particle flux (¹⁰Be/²³⁰Th) and the accumulation rate of authigenic uranium, which responds to the flux of organic carbon to the sea bed, both indicate a dramatic increase, compared to the present, in the export production of the Subantarctic zone (approximately the region between the present-day positions of the Subtropical Convergence and the Antarctic Polar Front) during glacial periods. If the South Atlantic is representative of the entire Southern Ocean, then export production in the Southern Ocean during the Last Glacial Maximum was substantially greater than at present. Previous studies, focusing on the burial of biogenic opal, failed to recognize the glacial increase in export production of the Southern Ocean because of a strong non-linearity between accumulation rates of opal and of organic carbon.