---

Siltation is a serious problem occurred in riverine harbors and estuaries. To overcome this problem and navigation control, continuous dredging is needed. To date, many approaches have been developed to reducing siltation in harbors.The objective of the current research study is to intoduce an cost effective structural method to control the siltation in riverine and tidal harbors. This method which is based on the flow pattern control at the entance of the harbor, is implementation of a current deflecting wall (CDW) at the harbor entrance. In the current study, the efficiency of the CDW was investigated for reducing sedimentation in reverine harbours and also the influence of geometrical specification of CDW on the hydrodynamic condition inside the harbor have been investigated. In the first step of the study, the hydrodynamic model was calibrated against experimental measurements cited in the literature. Then the model was applied to various alternatives of CDW shape, apex angle, length and location. Results obtained through numerical modeling experiments showed that around 30 percent reduction in harbor siltation could be achieved.

---

In this study, Plasma Electrolytic Oxidation (PEO) technique was used for generating ceramic layer on the surface of aluminum alloy AA2024-T6 and the effect of coating time on the electrochemical corrosion behavior, micro-hardness, morphology of coating, and the phase structure was studied. The alloy was coated in 1, 3, 5 and 7 minutes at a constant electrical potential 550 V in a sodium silicate solution 30 g/l. Coating surface morphology was studied by Scanning Electron Microscopy (SEM) and the electrochemical corrosion behavior was investigated by potentiodynamic and Electrochemical Impedance Spectroscopy (EIS) tests in 3.5 %wt. NaCl solution. Phases that generated during coating process were studied by X-Ray Diffraction (XRD) and hardness of coating was investigated by micro-hardness test. The results revealed that, as the coating time increases, the hardness value increases too. But, since the sample coated for 5 minutes exhibit the best morphology, it has shown the maximum corrosion resistance.

---

Time-growing navigation error due to inevitable measurement errors in the MEMS-grade inertial sensor is one of the main challenges in low-cost inertial navigation systems (INSs). This paper aims to develop AHRS/GPS/DR integrated navigation algorithm for long-range autonomous underwater vehicle (AUV). Proper performance in deals with long-term GPS outage is the main advantage of the proposed low-cost navigation algorithm. This is due to appropriate estimation of gyro biases in the proposed algorithm. Using Dead Reckoning (DR) method based on an axial speed sensor, an applied algorithm is developed for position estimation during the GPS outages. The algorithm is evaluated by field test executed on a long-range AUV with high underwater durability. Experimental results indicate that in spite of 500 seconds GPS outage, the estimation error in the heading angle does not exceed 5 degrees.

---

Using spudcan as foundations for jack-up rigs is usual. Model dimensions, consolidation of clay, and spudcan penetration are the most important issues in modelling of this type of foundations in clays. Penetration of CPT cones and spudcan foundations in single- layered clayey soils was investigated in this paper. Cement stabilized clay with 5 and 10 percent cement was used to study the effect of undrained shear strength of clay on load- penetration behavior of spudcan; Also, two CPT cones with different diameters were used to estimate the undrained shear strength of clay layers. Results show that cement stabilized clays can be used for modelling of clay layers with different strengths. However, careful attention should be paid for changing of bearing capacity factors in two cases, with or without cement. Results show that cones with smaller diameters can be used in physical modelling with good accuracy as well as conventional ones.