مهندسی دریا
Farnoosh Jahanbakhshi; Mohammad Reza Noorimehr; Mohammad Esmaeildoust
Abstract
Abstract- With growth of technology, the needs for data and information security over communication channels are necessary. One of the most important issues is the establishment of information security in marine communications. The RSA encryption algorithm is one of the most popular and most asymmetric ...
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Abstract- With growth of technology, the needs for data and information security over communication channels are necessary. One of the most important issues is the establishment of information security in marine communications. The RSA encryption algorithm is one of the most popular and most asymmetric algorithms used for secure data transfer. In the RSA encryption system, due to the very long key length, the encryption and decryption step speeds decrease, so it needs to improve its speed. One of the improving ways of RSA is RPrime RSA that includes the highest decryption of speed to RSA. In this paper, the encryption and decryption speed of RPrime RSA algorithm is improved using efficient residual number system. The result of implementation and comparison shows that the proposed method has an average of %22 and %36 improved at the encryption and decryption speed than the RPrime RSA algorithm.
مهندسی دریا
Elham Matori; Mohammad Esmaeildoust
Abstract
The PRINCE lightweight cryptographic algorithm was introduced as a template in 2012. In this paper, we intend to change the structure of the PRINCE encryption algorithm and use a Dynamic S-BOX to increase the complexity and security of the encryption process. In order to show the efficiency of the proposed ...
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The PRINCE lightweight cryptographic algorithm was introduced as a template in 2012. In this paper, we intend to change the structure of the PRINCE encryption algorithm and use a Dynamic S-BOX to increase the complexity and security of the encryption process. In order to show the efficiency of the proposed structure, differential analysis is performed on the algorithm as well as analysis on the optimal number of revolutions for the algorithm. Analyzes and implementations show that the cryptographic structure is more complex. Despite the slight increase in memory and execution time of the algorithm, compared to the PRINCE encryption algorithm with fixed S-BOX, it has more strength against differential attack and as a result, the security in the improved algorithm has increased. Stronger also increases security.
مهندسی دریا
Javad Ahsan; Mohammad Esmaeildoust; Amer Kaabi; vahid Zareii
Abstract
The residue number system has a parallel computational structure with carry-free operations and is widely used in cases such as digital signal processing, cryptography, design of FIR filters, etc. In this paper we design an efficient reverse converter for the four-moduli set {〖2^(n-2)+1,2〗^(n-3)-1,2^(n-3)+1,2^(n-5)-1}. ...
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The residue number system has a parallel computational structure with carry-free operations and is widely used in cases such as digital signal processing, cryptography, design of FIR filters, etc. In this paper we design an efficient reverse converter for the four-moduli set {〖2^(n-2)+1,2〗^(n-3)-1,2^(n-3)+1,2^(n-5)-1}. In this moduli set, due to the selection of well-formed and balanced modulus, it leads to optimal hardware implementation, with minimum area utilization and minimum time delay. The main advantage of this design is the use of a ROM free and adder base hardware structure. The proposed moduli set are relatively prime to most existed moduli sets in literature and as results it can be employed in the implementation of Montgomery multiplication. The proposed reverse converter has a two-level structure. In the first level, the Chinese remainder theorem is used, and in the second level, the Mixed-radix conversion is used to calculate the final weighted number. The results of computational theory show low time latency and minimal hardware space in this design.
مهندسی دریا
Ahmad Hajivand; Aghil Daraie
Abstract
The prediction of ship resistance is the most important part of the ship's hydrodynamic design. Nowadays, computational methods are used as a common tool for this purpose. Ship total resistance calculation by using two phase numerical method based on the Reynolds-averaged Naiver–Stokes solution ...
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The prediction of ship resistance is the most important part of the ship's hydrodynamic design. Nowadays, computational methods are used as a common tool for this purpose. Ship total resistance calculation by using two phase numerical method based on the Reynolds-averaged Naiver–Stokes solution requires high computational power. The idea of total resistance decomposition based on the physical cause is a basic principle in the ship hydrodynamic. In the proposed hybrid method, wave making resistance part is calculated by using Michell Integral and viscous part is computed by numerical solution of one phase viscous flow for double body condition. Computations are performed for 10 velocities from Fn = 0.06-0.62 and at each velocity the percentage of every component calculated. Hybrid method reduce computational time. To investigate the results, tow phase simulations are performed for a SWATH vessel. On average, there are 7% difference between the results obtained from hybrid and two phase method and computational time in hybrid method is 97% less than two phase method.
مهندسی دریا
Alireza Abdikian
Abstract
In this article, spectrum of the reflection, transmission and absorption of the thin metal nano-layer by using quantum hydrodynamic equations is studied. The thin metal nano-layer can be used to cover the equipment and devices to avoid detection which coated the outer surface of the submarines, ships, ...
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In this article, spectrum of the reflection, transmission and absorption of the thin metal nano-layer by using quantum hydrodynamic equations is studied. The thin metal nano-layer can be used to cover the equipment and devices to avoid detection which coated the outer surface of the submarines, ships, planes. It is also used the nano-layers to cover the various devices such as solar cells, glass reflex. In some devices, for example the solar cells, the more increase the absorption ratio, the more increase the efficiency and in some other devices, for example the reflex glasses, it is better to be high the reflection ratio. Hence, the study of the reflection, transmission and absorption ratio of electromagnetic waves are important in quantum plasma slabs. By combining the quantum hydrodynamic equations and the Maxwell's equations in the presence of a magnetic field can be obtained the coefficients of the reflection, transmission and absorption of electromagnetic waves in thin metal nano-layer in which we have taken the slab as quantum plasma. Clearly, it is shown that by taking term of the quantum Bohm's potential cause to appearance of the quantum refractive index for the Langmuir wave that this new refractive index does not have any similar relation in the classical plasma. Using the numerical values and the Mathematica software, the absorption coefficients have drawn in various conditions. This proposed method enables us practically to control the reflection or absorption power of electromagnetic waves in quantum plasma slab by adjusting a uniform external magnetic field.
مهندسی دریا
m y; Ehsan Gharibreza
Abstract
The ultimate goal of the electrical industry is to supply reliable energy. Therefore, accurate and on time detection of faults have always been the main concern of electricical utility users. In recent years, the use of cables has grown steadily and has made it difficult to detect faults and locations. ...
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The ultimate goal of the electrical industry is to supply reliable energy. Therefore, accurate and on time detection of faults have always been the main concern of electricical utility users. In recent years, the use of cables has grown steadily and has made it difficult to detect faults and locations. If the cable network is intended for a particular application, such as a generator connection cable to industrial power grid, its importance will be increased, and the Lack of timely performance of the protection system will cause irreparable damage. In this paper, a novel method is proposed for detecting and determining the location of faults in cable using a combined wavelet transform algorithm and an optimized MLP network with a bee algorithm. In the proposed algorithm, two initialization modules and prediction analyzes are proposed to increase the selection capability. The algorithm is done by the DigSILENT and MATLAB software and implemented on the ship industrial cable network. The simulation results indicate an accuracy of 93% for the considered algorithm in determining the correct location of the fault.
مهندسی دریا
Masoumeh beitabdollah; Mohammad Esmaeildoust; Amer Kaabi
Abstract
With growth of Technology, With growth of technology, the needs for data and information security over communication channels are necessary. Providing information security in marine environment includes communication between ships and also ships with ground station are one of the most important issues ...
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With growth of Technology, With growth of technology, the needs for data and information security over communication channels are necessary. Providing information security in marine environment includes communication between ships and also ships with ground station are one of the most important issues in information security. In order to provide Confidentiality, symmetric key cryptography algorithms such DES, 3DES, IDEA, RC6, Serpent and AES are presented by researchers. Different reports in literature are presented by researchers in order to compare the performance of these algorithms. Despite various considerations, the needs for deep comparison of these algorithms are needed. Therefore in this paper, deep consideration and comparison in the points of architecture, flexibility, security and speed of these algorithms are done. Based on the achieved results, the appropriate algorithm can be employed based on required flexibility, speed or desired levels of security. The result of implementation and comparison shows the advantages of AES algorithm in provided security and RC6 in speed of execution.
مهندسی دریا
M Moore; A. Firouzian nejad; S. ZiaeRad; A. Eidani nezhad
Abstract
The interest in bi-stable structures comes from their ability that these structures can have two different stable equilibrium configurations to define a discrete set of stable shapes. The geometrical changes occur with no need to continuously consume power, and mechanical hinges to preserve the structure ...
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The interest in bi-stable structures comes from their ability that these structures can have two different stable equilibrium configurations to define a discrete set of stable shapes. The geometrical changes occur with no need to continuously consume power, and mechanical hinges to preserve the structure in each stable shape.It is known that asymmetric composite laminates can have bi-stable response to different kind of loadings. In this research, the non-linear temperature-curvature relationship for the asymmetric composite laminates is studied using Rayleigh–Ritz technique. Attention is focused on studying the effect of material temperature dependency and resin layers; especially in the bifurcation point by use of analytical method. To this end, the well-known analytical theories are extended and used to consider the temperature dependency of material. The results obtained from the theory are then compared with the finite element simulations results and a good correlation is obtained. Finally, an experimental investigation is carried out and several specimens with [90/0]T, [70/–20]T and [70/20]T compositions were manufactured. In order to study the effect of resin layers, optical microscopy is utilized and the exact thickness of different layers in the manufactured specimens is determined. The thermal responses of the manufactured plates were measured and used to validate the results obtained from the analytical theory and finite element simulations
مهندسی دریا
M Kordnaeij; S.A Asghari Pari; S.M Sajjadi; M Shafai Bajestan
Abstract
In this study a porous obstacle was used to evaluate the performance of permeable obstacles for control of turbidity current. To build mathematical obstacle porous strata of 2.1 * 2.1 cm was used. 10 m long steep flume experiments are conducted. Tests were conducted in a double-dip 0 and 2.5 percent. ...
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In this study a porous obstacle was used to evaluate the performance of permeable obstacles for control of turbidity current. To build mathematical obstacle porous strata of 2.1 * 2.1 cm was used. 10 m long steep flume experiments are conducted. Tests were conducted in a double-dip 0 and 2.5 percent. Discharge constant in all tests was 0.7 liters per second. Feed concentration of 20 grams per liter of the concentrated flow and viscous flow in the upstream and downstream concentrations were measured porous barrier. Concentration was measured with use of a sampler flushing. The results showed that the porous barrier stepped porous barrier to the flow is better. Porous barrier stair staircase behind a thick flow of porous barrier and prevents over-stepped the stairs to the amount of sediment discharge reduced more.
مهندسی دریا
Tooba Heidari; nima shahni karamzadeh; Javad Ahadiyan
Abstract
In this study, results of experiments about the trajectory and the advance velocity of inclined and convergent rectangular surface jet into stagnant ambient have been presented. In order to discharge process simulation was used a flume with 3.2 m length, 0.6 m width and 0.9 m height and a rectangular ...
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In this study, results of experiments about the trajectory and the advance velocity of inclined and convergent rectangular surface jet into stagnant ambient have been presented. In order to discharge process simulation was used a flume with 3.2 m length, 0.6 m width and 0.9 m height and a rectangular channel with 6 cm width. Discharge channel was designed in the four angle of convergence 12.5, 25, 45 and 90 degree. This channel injected the jet stream to form of tangent to the surface of ambient and in three different slopes 0, 4 and 8 percent. Receiving fluid had been prepared from urban water. As well as the jet fluid had been prepared from the salt liquidation in water and in three concentrations 5, 15 and 45 gr/l. After running the experiments and using of images routing process were analyzed the data. In this regard, hydraulic and geometric parameters on the trajectory and the advance velocity of jet was investigated. According to the results, increase the slope and decrease the angle of convergence causes increase in length of trajectory and decrease in the advance velocity of jet. Reduce the densimetric froude number causes decrease in length of trajectory. Also, in order to investigate of influence of convergence on the movement path of flow, by comparison of trajectory in convergent channel and simple channel, More relative advance was seen in convergent channel. Finally, using of the data analysis, relation between advance velocity of jet and dependent parameters was determined with RMSE=0.034.
مهندسی دریا
Mahboobeh Golaghapoor Kami; Mostafa Jafarzadeh Khatibani; Etemadaldin Rabei Gholami
Abstract
For all new ships sea trials should be carried out as a part of the delivery from the yard to the ship owner. An important part of the delivery sea trial is to determine the speed capability of the ship in the contractual condition, which is traditionally deep, calm water and no wind, at some specified ...
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For all new ships sea trials should be carried out as a part of the delivery from the yard to the ship owner. An important part of the delivery sea trial is to determine the speed capability of the ship in the contractual condition, which is traditionally deep, calm water and no wind, at some specified loading condition. However, it is seldom possible to perform this particular test under such conditions, and when the test is done in other conditions, the result is corrected back to the contractual condition. The correction can be of a significant magnitude. The correction procedure can be influenced by different parameters such as wind resistance, shallow water effect, sea currents and added resistance due to diffraction. There are different experimental methods for correction of measured speed. Since the latter parameter is the most important between others, In this article added resistance due to diffraction has been calculated for three ships using existing methods and comparisoned with the speed correction result of shipbuilder company (Hyundai Heavy Industries). The results show considerable deviation between HHI sea trial speed correction method and other methods. So HHI added resistance calculation method needs to be revised.
مهندسی دریا
seyed khalil shariati; s m
Abstract
In the conceptual design of a submarine quick estimation of hydrodynamic coefficients of a body and appendages is needed. In these methods, formulas are given for different coefficients and for the control surfaces, using two-dimensional factor provided for hydrofoil in wing sections theory books, are ...
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In the conceptual design of a submarine quick estimation of hydrodynamic coefficients of a body and appendages is needed. In these methods, formulas are given for different coefficients and for the control surfaces, using two-dimensional factor provided for hydrofoil in wing sections theory books, are suggested. A Critical point in using these coefficients of wing sections theory books is, these coefficients are calculated for far from the free surface and for near the free surface is needed to be improved. Then in In the present work, Based on the assumption of potential flow and boundary element method a computer program has been developed to calculate the coefficient of hydrofoils with various sections in near the free surface. results in submerged is in full compliance with experimental and numerical results and in the near the free surface, these results are consistent with good accuracy.
مهندسی دریا
Abdullah Eidani nezhad; A.Kabir Kabiri; S.H. Dibajian; A. Mardan
Abstract
There is an increasing interest in the marine industry to use composites to improve the hydrodynamic and structural performance of naval structures. The materials used within the composite are commercially available, and it is important the development of the right mix of fibers, resin and laminate lay-up ...
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There is an increasing interest in the marine industry to use composites to improve the hydrodynamic and structural performance of naval structures. The materials used within the composite are commercially available, and it is important the development of the right mix of fibers, resin and laminate lay-up that provide the desired mechanical and environmental performance for marine application. In this paper, to improve the stiffness and control the geometry of the blades of a marine propeller made of carbon/epoxy genetic algorithm to determination of optimal stacking Sequence is used. Using this method will minimize the deformation of tip blades. The optimization process has executed by linking ABAQUS and MATLAB software. Optimal angles of blade propeller obtained by using this process.
مهندسی دریا
ahmad rezaie mazyak; mehdi sanayei
Abstract
The main goal of using floating breakwaters is to provide the sheltered area of calm water in the coastal zone. In present research, for analyzing hydrodynamic modeling of pontoon floating breakwaters the AQWA module of ANSYS software has been selected. The main parameters that have been considered in ...
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The main goal of using floating breakwaters is to provide the sheltered area of calm water in the coastal zone. In present research, for analyzing hydrodynamic modeling of pontoon floating breakwaters the AQWA module of ANSYS software has been selected. The main parameters that have been considered in this research are pattern of significant wave height, wave period, and draft and width of floating pontoon. Wave transmission coefficient can be obtained from water surface changes in any point of leeward. Results of numerical modeling demonstrate that a pontoon floating breakwater with relative width greater than 0.4 have appropriate performance. Also it has been found that the transmission coefficient of pontoon floating breakwaters will be in the range of 0.35 to 0.60 if the relative wave period changes in the range of 1.5 to 4.
مهندسی دریا
Mohammad Khedmati; Mahdi Omidali; Roohollah Hadipoor Goodarzi
Abstract
A common way to join dissimilar materials in industrial applications is to use adhesives. Marine industries use this kind of joints for attaching main hull to superstructure of the ships. Most previous researches have focused on composite-composite joints, while a few of them are devoted to aluminum- ...
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A common way to join dissimilar materials in industrial applications is to use adhesives. Marine industries use this kind of joints for attaching main hull to superstructure of the ships. Most previous researches have focused on composite-composite joints, while a few of them are devoted to aluminum- sandwich panel joints. This study focuses on the numerical static strength analysis of a typical aluminum-sandwich panel T-joints and improving its strength through a novel design. The results of numerical analyses are in a good agreement with those of the experimental tests and confirm the accuracy of numerical analyses. In analyzing the adhesive between joint elements, contact elements and cohesive zone model (CZM) in ANSYS as well as nonlinear analysis is used. Results show that change in joint geometry considered in this paper, caused a 7.25% increase in vertical failure load of the joint. This increase in strength of joint attained in a situation that because of the merging of the joined parts, the process of construction became easier.
مهندسی دریا
Saeed Shadkam; EatemadO’Din Rabei Gholami; Nasim Al Ali
Abstract
Each Ship Can Transfer Safely in certain Zone According to It`s Stability and Regime of Sea State. Therefore, if Ship Have to Pass in Specific Condition that Sea State is Jumpy, Should be Provide One or More Anti Rolling Methods to Survive. The Purpose of this Article is Reduction and Control of Rolling ...
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Each Ship Can Transfer Safely in certain Zone According to It`s Stability and Regime of Sea State. Therefore, if Ship Have to Pass in Specific Condition that Sea State is Jumpy, Should be Provide One or More Anti Rolling Methods to Survive. The Purpose of this Article is Reduction and Control of Rolling Motion to Reach Proper Hydrostatic Stability with Assessment Activity of Two Methods Using Commonly to Reduce Rolling Motion. This Methods are Activated Anti Rolling Tanks And Gyroscope. In this Article Trying to Solve Its Equations in Matlab Software and Compare it to Reach More Activity Method. The Results Shown that Anti Rolling Method Proposed for Large Displacement Ships and Otherwise Gyroscope is More Activity for Passenger Ships and Small Vessels.
مهندسی دریا
Morteza Bakhtiari; seyed mahmood kashefipour; Mehdi GHomeshi
Abstract
One application of spur dikes is ensure navigability of rivers Through regulation and stabilization of sufficient width and depth, balance changes for the development of depth and The radius of curvature.Nowadays, spurs are also employed for promoting environmental conditions along a riverbank. One of ...
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One application of spur dikes is ensure navigability of rivers Through regulation and stabilization of sufficient width and depth, balance changes for the development of depth and The radius of curvature.Nowadays, spurs are also employed for promoting environmental conditions along a riverbank. One of the important topics abut spurs is their protection against scouring that has been less studied. One of the simple and economic ways for protection of spur against scouring is using riprap. Riprap is very common because it is easily available, cheap and simple for construction.Since using, spur dikes to protect riverbanks spatially in bends is very common, This research was carried out in order to investigate the effect of the structure stability. The purpose of this study is evaluation of depth-placed riprap for protection of spur dike in 90° Bend. In order to achieve the research objectives, one riprap size of inch diameter was used. Ripraps are placed in 3 depths ( ), and used for 3 lengths of spur(15%,20% and 25% width of flume), two angles (90 and 120 degree) and three longitude distance (3,5 and 7 times of spur length). Parameters as variables in this study were selected which The results can be used in large rivers, including navigable rivers and the Gulf.The results showed that stability of ripraps are increased with increasing the depth-placed riprap and angle of spurs, whereas increasing in spur length and longitude distance decreases stability of ripraps.
مهندسی دریا
Ataollah Gharechahi; Mohammad , Rahimi
Abstract
In this paper the amount of pollution produced by boats with 2-stroke engines have been calculated, in different seasons in southern coast of Iran. The seasonal activity of boats is estimated based on the average of wide range of expert opinion whom familiar with these type of vessel according to crowd ...
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In this paper the amount of pollution produced by boats with 2-stroke engines have been calculated, in different seasons in southern coast of Iran. The seasonal activity of boats is estimated based on the average of wide range of expert opinion whom familiar with these type of vessel according to crowd wisdom theorem. Also the amount pollution per hours power of engine is derivates from similar international researches.The results show that the proportion of pollution from these boats is about 290 times greater than pollution from stern tube and deck machinery leakage from vessels in southern Iran. In particular, they are contains toxic compounds of BTEX which is generated in way of marine life near coastal waters. In spring and winter the pollution is greater than other seasons. with emphasis on the Persian Gulf and Oman Sea are the “Especial Area” and the threat of activity of boats on marine life; Suitable solution to reduce the pollution from these vessels, Should be in priority program of coastal countries especially the Islamic Republic of Iran .
مهندسی دریا
Seyed Amin Asghari Pari; Seyed Malek Mohagheghiyan
Abstract
Turbidity currents are one of the most fundamental factors that transferring sediment near the dam. In this article, the effect of roughness, pattern, height and the shape of roughness in the floor on controlling turbidity current are studied using finite elements numerical method by ANSYS-CFX. For solving ...
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Turbidity currents are one of the most fundamental factors that transferring sediment near the dam. In this article, the effect of roughness, pattern, height and the shape of roughness in the floor on controlling turbidity current are studied using finite elements numerical method by ANSYS-CFX. For solving turbulence equations are used K-e method. After calibrating of model has done, at the first, simulated flow without roughness and then three shape of roughness pyramid-shaped, round edge cylindrical and cubic with two alternative zigzag and consecutive, with 5 different height and for subcritical and supercritical flow regime are modeled. The results indicated that with the increase in height of the roughness and cross flow and with zigzag arrangement, reduced the turbidity current discharge. Also the effect of roughness on controlling subcritical turbidity current are more than supercritical flow.
مهندسی دریا
khosro fazelpoor
Abstract
In order to provide SST images, the sensor MODIS installed on Aqua Satellite EOS-1 was used. Applying lighting assessment out of images from Modis 21-Level 1B Calibrated Radiances -1km in Persian Gulf and the Bushehr sea station (Bouyeh) from global algorithm specified for above sensor was used to estimate ...
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In order to provide SST images, the sensor MODIS installed on Aqua Satellite EOS-1 was used. Applying lighting assessment out of images from Modis 21-Level 1B Calibrated Radiances -1km in Persian Gulf and the Bushehr sea station (Bouyeh) from global algorithm specified for above sensor was used to estimate the sea surface temperature. With function of Matlab software to extract data of satellite images, and GIS software to convert the matris obtained, the maps of sea surface temperature were used. Forty eight images taken in 2008, 2009, 2012, and 2013 were selected. Their correlation coefficient eventually was 0.75, 0.86, and 0.75 respectively. Likewise the special coefficient obtained as 0.86, 0.90, 0.94 and 0.86 respectively. Finally, taking the 31 band temperature into consideration for the years 2008, 2009, 2012 and temperature differences of bands 31 and 32 and the sensor angle as independent factors were used at Bouyeh temperature as an affiliated factor calibrated by SPSS software for global algorithm of Persian Gulf. In order to check the correctness the algorithm suggested, the sea surface temperature was re-examined with satellite images of the year 2013; the correlation coefficient 0.96 and 0.94 were obtained. The searching has shown that the depth with current sea and latitude have effect on sea surface temperature, and temperature balance specially in north and central latitude have contrary relation with depth.
مهندسی دریا
Mahpeykar, Omid; Masoud Sadrinasab; , Morteza Bakhtiari; , Nima Shahni karamzadeh
Abstract
Developed countries are using renewable energy in order to minimize emission of harmful gases, and many countries are studied new designs. Which uses of the later is increasing rapidly. One of the cleanest renewable ocean energy is using the potential of tidal energy. Studies show that the best place ...
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Developed countries are using renewable energy in order to minimize emission of harmful gases, and many countries are studied new designs. Which uses of the later is increasing rapidly. One of the cleanest renewable ocean energy is using the potential of tidal energy. Studies show that the best place for obtaining tidal energy in the Persian Gulf and is the Doragh Estuary, which is located in the northern part of the Persian Gulf. This estuary is the unique area in the Persian Gulf with more than 5 meters tidal range which has the potential to produces maximum tidal energy in this region.In this study, a physical model of Doragh estuary is constructed and employed a pumping system as well as a source of water to create tide in the model. Also two dams are made somehow in the model to reserve water behind these dams during ebb and flood. A propeller which is connected to a turbine is fixed to one of the dams, and works during both ebb and flood in which transfers movement of propeller into electricity. Electrical current is connected to an instrument which show the amount of produced electricity in the model. The results of the model show that by increasing tidal range, electricity increases electricity exponentially. In this experiment the model run with different scenarios to get maximum efficiency which is recorded to 15% during flood and producing of electrical power can increased by 30 to 50 percent during both ebb and flood.
مهندسی دریا
A. Mohammad Rahimi; Mohammad Khedmati
Abstract
Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess ...
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Grillages consisting of intersecting beams are supporting shell structures of the ships in different places such as bottom, deck and sides. Different methods available for strength analysis of plated grillages are studied from the viewpoints of characteristics and limitations. Finally, the way to assess the strength of such structural elements is investigated. This study is based on preparation of a soft-ware for analysing the grillages. Using the software, it is possible to analyse grillages used in the ships’ structures for any type of boundary and loading conditions that are simply selectable by users. Getting the required input data from the user, elastic deflections and stresses induced as a result of applying concentrated or distributed loads are calculated at the intersections of the longitudinal and transverse members, relieving the need to complicated numerical calculations.
مهندسی دریا
Reza Movahedinia; Mirabdolhamid Mehrdad; Saeed pourzeynali
Abstract
Jacket-type offshore platforms play an important role in oil and gas industries in shallow and intermediate water depths such as Persian Gulf region. Such important structures need accurate considerations in analysis, design and assessment procedures. Incremental wave analysis for performance-based assessment ...
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Jacket-type offshore platforms play an important role in oil and gas industries in shallow and intermediate water depths such as Persian Gulf region. Such important structures need accurate considerations in analysis, design and assessment procedures. Incremental wave analysis for performance-based assessment of jacket platforms is established in 2011 to estimate different limit states and accurate behavior of jacket platform against environmental wave loading. IWA can be appropriate substitute to current pushover practice. The IWA can estimate the collapse-prevention limit state of jacket platforms properly. In addition, an appropriate parameter for ultimate capacity of offshore platforms is introduced which is called Collapse Wave Height (CWH). The CWH can be utilized as a substitute to RSR parameter in the design and assessment of jacket platforms. In this paper, IWA is explained. IWA curves, collapse-prevention limit state and CWH for case study platform is calculated. Effect of deck mass and its distribution on CWH is examined.
مهندسی دریا
sajad sadr; Mohamad Hosein Khanzade
Abstract
According to recent advances in military science and electrical engineering on the one hand and on the other hand, subject of replacing diesel engines with electro motors (due to higher efficiency, less maintenance, better performance, better dynamics, etc.), this paper discuss about electric ships and ...
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According to recent advances in military science and electrical engineering on the one hand and on the other hand, subject of replacing diesel engines with electro motors (due to higher efficiency, less maintenance, better performance, better dynamics, etc.), this paper discuss about electric ships and simulation of the boat drives with electric motors. Since the construction of electro motors up to 1970th (which is the start point of Power Electronic that result in speed control of AC motors), the propulsion system hadn’t been use system uses electric motors. But after that, due to the high response rate, quick start, high efficiency, good reliability, easy maintenance and low cost ... Day by day the use of AC motors became more significant. Since Modeling and Simulation of vector control of AC motor for boat propulsion (with Load model) hasn’t been written as an detailed article, so the purpose of this paper is analyze of vector control performance of induction motor as vessels motor. The Contents of this article is this respect; after Introduction, various components of the propulsion system are discussed that with Load model will give propulsion system of vessel. In this paper after describe of vessel propulsion system, the vessel with electric propulsion motors has been discussed and finally an electric propulsion system for typical vessel is designed. The result of modeling and simulation of this project in conclusion part is discussed.