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October 01, 2018
Because most of the pumps on board ship are centrifugal pumps, we will examine the symptoms and common causes of centrifugal pump problems here.
Centrifugal pumps work, as the name suggests, on the centrifugal forces acting on the liquid being pumped. 

The centrifugal force is imparted to the liquid through the high-speed rotation of a specially shaped impeller.
Whenever we find a centrifugal pump not performing well, the causes can usually be traced back to 3 common reasons:
●      Suction related problem
●      System related problem
●      Mechanical related problem
Now you can easily pinpoint the trouble. Download free DiagnoPump, the pump troubleshooter software.


Suction Related Problem
The liquid inside the impeller must behave like a solid column in order for the centrifugal pump to work. More liquid must replace whatever liquid forced out by centrifugal force. If the solid column of liquid is broken, by the presence of air, the pumping effect is reduced or broken, and the pump does not perform properly. Some of the common suction related faults are:
●      Pump not primed
●      Pump suction pipe not completely filled with liquid
●      Suction lift too high
●      Insufficient margin between suction pressure and vapor pressure
●      Excessive amount of air or gas in the liquid
●      Air pockets in the suction line
●      Air leaks into the suction line
●      Air leaks into the pump through the stuffing box or gland
●      Foot valve too small
●      Foot valve partially clogged
●      Inlet of suction pipe insufficiently submerged
●      Water seal pipe plugged
●      Seal cage improperly located in stuffing box, preventing sealing fluid entering space to form a seal
System Related Problem
Most of the system related problems occur because of design flaw. For example, the designer may have chosen the wrong pump whose characteristic does not match the system requirement. For the Marine Engineer working on board ship, these problems are rare. Perhaps sometimes, when replacing motors, and starting up. Below are some of the common reasons:
●      Speed too low
●      Speed too high
●      Wrong direction of rotation
●      The total head of system higher than design pump head
●      The total head of system lower than design pump head
●      Specific gravity of liquid different from design
●      Viscosity of liquid differs from that for which the pump was designed
●      Operation at very low capacity
●      Parallel operation of pumps unsuitable for such operation
Mechanical Related Problem
This group of problems is most often encountered on board ship. The effects of mechanical related problems could manifest themselves as suction related problems, like air leaks in the system, worn out impellers, and mouth rings, but the most common occurrence is the presence of vibration and abnormal noise in the equipment.
All equipment on board ship, including centrifugal pumps will encounter mechanical related problems. The practice of good maintenance, and vigilant watchkeeping will lessen the damage to the equipment. Some of the common mechanical related problems are:
●      Foreign matter in the impeller
●      Misalignment
●      Foundations not rigid
●      Shaft bent
●      Rotating part rubbing on stationary part
●      Bearing worn
●      Wearing rings worn
●      Impeller damaged
●      Casing gasket defective, permitting internal leakage
●      Shaft or shaft sleeves worn or scored at the packing
●      Packing improperly installed
●      Incorrect type of packing for operating conditions
●      Shaft running off-center because of worn bearings or misalignment
●      Rotor out of balance, resulting in vibration
●      Gland too tight, resulting in no flow of liquid to lubricate the packing
●      Failure to provide cooling liquid to water-cooled stuffing boxes
●      Excessive clearance at bottom of stuffing box between shaft and casing, causing packing to be forced into pump interior
●      Dirt or grit in sealing liquid, leading to scoring of shaft or shaft sleeve
●      Excessive thrust caused by a mechanical failure inside the pump or by the failure of the hydraulic balancing device, if any.
●      Excessive grease or oil in anti-friction bearing housing or lack of cooling, causing excessive bearing temperature
●      Lack of lubrication
●      Improper installation of anti-friction bearings
●      Dirt getting into bearings
●      Rusting of bearings due to water getting into housing
●      Excessive cooling of water cooled bearing, resulting in condensation of moisture from the atmosphere in the bearing housing




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October 01, 2018
I have collected a few interesting project topics in Digital Signal Processing with abstracts for you. Read it and do your project.

1.TRACKING AND COUNTING PEOPLE IN VISUAL SURVEILLANCE SYSTEMS [IEEE 2011]

ABSTRACT The greatest challenge on monitoring characters from a monocular video scene is to track targets under occlusion conditions. In this work, we present a scheme to automatically track and count people in a surveillance system. First, a dynamic background subtraction module is employed to model light variation and then to determine pedestrian objects from a static scene. To identify foreground objects as characters, positions and sizes of foreground regions are treated as decision features. Moreover, the performance to track individuals is improved by using the modified overlap tracker, which investigates the centroid distance between neighboring objects to help on target tracking in occlusion states of merging and splitting. On the experiments of tracking and counting people in three video sequences, the results exhibit that the proposed scheme can improve the averaged detection ratio about 10% as compared to the conventional work.

2. DESIGN AND OPTIMIZATION OF THE MOVING OBJECT DETECTING SYSTEM BASED ON BLACKFIN DSP [IEEE 2010]

Abstract – Based on Blackfin DSP, we design and implement a compact moving object detecting and video recording system. The background subtraction algorithm is applied to the system to detect the moving objects. And when there is any object being detected, the frames containing the moving objects will be recorded automatically. In order to improve the accuracy of the detecting results, in this paper, instead of using the median filter, we design the block filtering algorithm to filter the noise with the simply connected block region, since the block filtering algorithm needs far less amount of computation than the median filtering algorithm. Further, in order to improve the detecting speed, based on the memory configuration of the system, a new block based parallel data processing mechanism is proposed, in which the external memory data to be processed is moved into the internal memory space in advance that greatly reduces the external memory access requests of the DSP core, thus good parallel data processing and transmission is achieved. The results of the experiments demonstrate that the block filtering algorithm is more suitable for a real time system than the median filter, because the block filtering algorithm improves the filtering efficiency greatly by reducing the amount of filtering computation and also works with satisfying statistical accuracy. In addition, the results of the experiments also show that the block based parallel data processing mechanism is highly effective in improving detecting speed and contributes to a more efficient parallel detecting system.

3. AN IMPROVED MEDIAN FILTERING ALGORITHM COMBINED WITH AVERAGE FILTERING [IEEE 2011]

Abstract—To solve the contradiction between the noise reducing effect and the time complexity of the standard median filter algorithm, the paper proposed an improved median filter algorithm combined with average filtering. According to the correlation of the image, the algorithm adaptively resizes the filter mask according to noise levels of the mask. According to the sorting results of the selected pixel values in the neighborhood, the algorithm uses the median to replace the original pixel. Experimental results show that the improved algorithm can effectively reduce time complexity and has better noise-reducing effect than the standard median filter algorithm. It has a good application prospect in image processing.

4. RESEARCH AND IMPLEMENTATION OF INFORMATION HIDING BASED ON RSA AND HVS [IEEE 2011]

Abstract: To better protect the security of information, this paper proposed an information transmission scheme which combined the cryptosystem and information hiding. The scheme pretreated the information firstly by making use of the RSA arithmetic which belongs to the public key cryptosystem, and then took advantage of the improved LSB which based on the Human Visual System to make the cryptograph hid in the 24 bits BMP image and transmitted it. The embedding and extracting process of secret information in the scheme were discussed in detail. Also, the result of information hiding achieved by this scheme was given. The principle of the scheme is simple, and it is easy to implement. The experimental result suggests that the scheme is efficient and has good practical value.

5. PERFORMANCE ANALYSIS OF INTEGER WAVELET TRANSFORM FOR IMAGE COMPRESSION [IEEE 2011]

Abstract— For image compression, it is very necessary that the selection of transform should reduce the size of the resultant data as compared to the original data set .In this paper, a new lossless image compression method is proposed. For continuous and discrete time cases, wavelet transform and wavelet packet transform has emerged as popular techniques. While integer wavelet using the lifting scheme significantly reduces the computation time, we propose a completely new approach for further speeding up the computation. First, wavelet packet transform (WPT) and lifting scheme (LS) are described. Then an application of the LS to WPT is presented which leads to the generation of integer wavelet packet transform (IWPT). The proposed method, Integer Wavelet Packet Transform (IWPT) yields a representation which can be lossless, as it maps an integer valued sequence onto the integer valued coefficients. The idea of Wavelet Packet Tree is used to transform the still and color images. IWPT tree can be built by iterating the single wavelet decomposition step on both the low-pass and high-pass branches, with rounding off in order to achieve the integer transforms. Thus, the proposed method provides good compression ratio.

6. DESIGN OF A COLOR IMAGE FUSION SYSTEM BASED ON DSP AND FPGA [IEEE 2010]

Abstract—In this paper, a color image fusion system based on DSP and FPGA is introduced .In the system, TMS320DM642 is used as the kernel processor to finish the images fusion arithmetic, storage and display. FPGA, which has the ability to control the logic of image capturing, is used as the assistive processor. The experiment shows that this technology can obtain color fusion image.

7. THE PORTABLE WIRELESS AERIAL IMAGE TRANSMISSION SYSTEM BASED ON DSP [IEEE 2010]

Abstract-The paper provides portable digital aerial image system based on Blackfin DSP. The system includes the aeromodelling carrier part and the ground control part. The image transmission between the two parts realized with Nordic Semiconductors RF transceiver nRF24L01. The aeromodelling-carrier part takes pictures using CMOS image sensor and compresses data by ADSPBF531, then sends them to ground part wirelessly. The ground control center based on ADSP-BF533 supervises images real time and samples data. After relevant subsequent image processing and compressing, the final image is saved locally. In controllable range, the system can take pictures anyplace and any angle, can lock object neatly. This system features double DSP architecture so it can transmit and process image very fast. It is small, light, low power consumption and low cost. It is easy for single taking and operation, so has good application prospect in field reconnaissance, traffic surveillance, city layout and the situation of bad weather or a disaster and so on.

8.DETECTING BACKGROUND SETTING FOR DYNAMIC SCENE [IEEE 2011]

Abstract – Processing Real-Time image sequence is now possible because of advancement of technological developments in digital signal processing, wide-band communication, and high-performance VLSI. With the developments in video technology, the surveillance system can be built with some low cost gadget such as the web-camera. In this modern life with increasing number of crime rate, people in society need for security and safety; video surveillance has become important reason to oppose threats of crime and terrorism. The most fundamental part of surveillance is foreground detection, which is retrieval of an object of interest. The object of interest can remodel by common background subtraction technique. There is some problem arises by using this technique, where because of variation of light source, the background constantly changes. The intensity of pixel changes throughout the object detection takes place. Intensity of pixel value changes leads to improper foreground detection, the background detected as foreground object. This paper proposes a method to model and update the background of the scene by intersection solving method.

9.A VIEW ON LATEST AUDIO STEGANOGRAPHY TECHNIQUES [IEEE 2011]

Abstract—Steganography has been proposed as a new alternative technique to enforce data security. Lately, novel and versatile audio steganographic methods have been proposed. A perfect audio Steganographic technique aim at embedding data in an imperceptible, robust and secure way and then extracting it by authorized people. Hence, up to date the main challenge in digital audio steganography is to obtain robust high capacity steganographic systems. Leaning towards designing a system that ensures high capacity or robustness and security of embedded data has led to great diversity in the existing steganographic techniques. In this paper, we present a current state of art literature in digital audio steganographic techniques. We explore their potentials and limitations to ensure secure communication. A comparison and an evaluation for the reviewed techniques is also presented in this paper.

10.A REAL-TIME VISION SYSTEM FOR NIGHTTIME VEHICLE DETECTION AND TRAFFIC SURVEILLANCE(IEEE MAY 2011)

Abstract—This paper presents an effective traffic surveillance system for detecting and tracking moving vehicles in nighttime traffic scenes. The proposed method identifies vehicles by detecting and locating vehicle headlights and taillights using image segmentation and pattern analysis techniques. First, a fast bright-object segmentation process based on automatic multilevel histogram thresholding is applied to effectively extract bright objects of interest. This automatic multilevel thresholding approach provides a robust and adaptable detection system that operates well under various nighttime illumination conditions. The extracted bright objects are then processed by a spatial clustering and tracking procedure that locates and analyzes the spatial and temporal features of vehicle light patterns, and identifies and classifies moving cars and motorbikes in traffic scenes. The proposed real-time vision system has also been implemented and evaluated on a TI DM642 DSP-based embedded platform. The system is set up on elevated platforms to perform traffic surveillance on real highways and urban roads. Experimental results demonstrate that the proposed traffic surveillance approach is feasible and effective for vehicle detection and identification in various nighttime environments.


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October 01, 2018

Introduction Definitions and Basics

●      Aggregate Supply, at Answers.com
●      The total supply of goods and services produced within an economy at a given overall price level in a given time period. It is represented by the aggregate-supply curve, which describes the relationship between price levels and the quantity of output that firms are willing to provide. Normally, there is a positive relationship between aggregate supply and the price level. Rising prices are usually signals for businesses to expand production to meet a higher level of aggregate demand.
●      New Classical Macroeconomics, from the Concise Encyclopedia of Economics
●      Shocks to aggregate supply are typically changes in productivity that may result, for example, from transient changes to technology, prices of raw materials, or the organization of production. Ideally, firms would choose to produce more and to pay their workers more when the economy has been hit by favorable shocks and less when hit by unfavorable shocks. Similarly, workers would be willing to work more when productivity and wage rates are higher and to take more leisure when their rewards are lower. For both, the rule is "make hay while the sun shines."...
●      National Income Accounts, from the Concise Encyclopedia of Economics
●      The broadest and most widely used measure of national income is gross domestic product (GDP), the value of expenditures on final goods and services at market prices produced by domestic factors of production (labor, capital, materials) during the year. It is also the market value of these domestic-based factors (adjusted for indirect business taxes and subsidies) entering into production of final goods and services. "Gross" implies that no deduction for the reduction in the stock of plant and equipment due to wear and tear has been applied to the measurements and survey-based estimates. "Domestic" means that the GDP includes only production by factors located in the country--whether home or foreign owned. GDP includes the production and income of foreigners and foreign-owned property in the home country and excludes the production and incomes of the country's own citizens or their property located abroad....

In the News and Examples

●      OPEC, from the Concise Encyclopedia of Economics
●      Despite what many noneconomists believe, the 1973-1974 price increase was not caused by the oil "embargo" (refusal to sell) that the Arab members of OPEC directed at the United States and the Netherlands. Instead, OPEC reduced its production of crude oil, raising world market prices sharply. The embargo against the United States and the Netherlands had no effect whatsoever: people in both nations were able to obtain oil at the same prices as people in all other nations. This failure of the embargo was predictable, in that oil is a "fungible" commodity that can be resold among buyers....
●      Inflation, from the Concise Encyclopedia of Economics
●      Some economists call the above analysis a "demand-pull" explanation (monetary expansion fuels spending that pulls prices up), while proposing a "cost-push" alternative. For particular episodes of inflation, they have variously blamed monopolies, labor unions, OPEC, and even the failure of the anchovy harvest off Peru for pushing up prices. The equation of exchange warns us that for a "supply shock" to account for a large rise in the general price level (not just a relative rise in some prices, such as the price of oil), the economy's output must shrink by a large percentage. In practice, "supply shock" cases are seldom large enough to account for much inflation and are typically short-lived....

A Little History: Primary Sources and References

●      Jean-Baptiste Say, biography from the Concise Encyclopedia of Economics
●      Say's Law has various interpretations. The long-run version is that there cannot be overproduction of goods in general for a very long time because those who produce the goods, by their act of producing, produce the purchasing power to buy other goods. Say wrote: "How could it be possible that there should now be bought and sold in France five or six times as many commodities as in the miserable reign of Charles VI?" With this statement Say had the long run in mind. Certainly the long-run version is correct. Given enough time, supply does create its own demand. There can be no long-run glut of goods.
●      But Say also had a short-run version, that even in the short run there could be no overproduction of goods relative to demand. It was this version that Malthus attacked in the nineteenth century and that Keynes attacked in the twentieth century. They were right to attack it....




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October 01, 2018
Plastic is an organic material prepared out of resin. It may or may not contain fillers, plasticisers and solvents. Plastic may be defined as a natural or synthetic organic material which are having the property of being plastic at some stage of their manufacture when they can be moulded to required size and shape.
Shellac and bitumen are the natural resins used as plastic for a long time. In 1907, Blackland produced synthetic resin from the reaction of phenol and formaldehyde. The resin was hardened under pressure and heat to produce useful plastic articles.
Types of Plastics
Primarily there are two types of plastics:
1. Thermosetting and
2. Thermoplastic.
1. Thermosetting Plastics: It needs momentary heated condition and great pressure during shaping. When heated cross linkage is established between the molecules and chemical reaction takes place. During this stage shape can be changed with pressure. This change is not reversible. The scrap of such plastic is not reusable. Bakelite is an example of such plastic.

2. Thermoplastic: In this variety, the linkage between the molecules is very loose. They can be softened by heating repeatedly. This property helps for reuse of waste plastic. These plastic need time to cool down and harden. These plastics are to be kept in moulds till cooling takes place completely. Bitumen, cellulose and shellac are the examples of this variety of plastics.
Properties of Plastics
1. Colour: Some plastics are completely transparent. Using pigments plastics of any attractive colour can be produced.
2. Dimensional Stability: It is dimensionally stable to a great extent.
3. Durability: Plastic offers great resistance to moisture and chemicals and hence more durable.
4. Electrical Insulation: The plastics possess excellent electrical insulating property.
5. Fire Resistance: The phenol-formaldehyde and urea-formaldehyde plastics resist fire to a great extent and hence they are used as fire proofing materials.
6. Strength: The plastics are reasonably strong. Their strength may be increased by reinforcing with various fibrous materials. Attempts are being made to produce structurally sound plastics.
7. Specific Gravity: The specific gravity of plastics is very low and hence convenient to handle.
8. Ductility: The plastics are not ductile and hence they fail without giving warning.
9. Fixing: Plastics can be bolted, drilled, glued, clamped or simply push fitted in position.
10. Maintenance: There is no maintenance cost for plastic articles i.e., they do not need painting and polishing.


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October 01, 2018
The radiation sensitivity of silver halides ends for all practical purposes at about 525 mm . In Figure 3 Curve A illustrates the spectral sensitivity of a typical silver bromo-iodide emulsion and B illustrates the average human visual response curve. As the curves show, the maximum response of the eye is in the yellow-green near 550 mm which lies beyond the sensitivity range of the emulsion, which is much more sensitive to the violet and blue than the eye.
Figure 3: Curves Approximating the
Light Sensitivity of Typical Silver
Halide Crystals (blue) and
                                                                                 the Human Eye (yellow)                 
The sensitivity of the silver halides may be extended to radiation of longer wavelengths by the addition of dyes or "color sensitizers." Although referred to as dyes, color sensitizers are not ordinary dyes in that they are not used to colorcloth or other materials.
Emulsion sensitizing results from the absorption of radiant energy by the dye at a wavelength that would not affect the silver halide, and the transfer of that "exposure" energy to the silver halide to form a latent image and make the affected grain developable. If a dye is a sensitizer, then its action depends upon the absorption characteristics of the silver halide-adsorbed color sensitizer complex, which may be quite different from the absorption of the dye itself. Since the sensitivity of such dyes varies greatly, it is often necessary to use a combination of materials to obtain a specific result. Some combinations, however, do not work well together, so that the system balance must be carefully studied before the final emulsion composition is determined. There are substances that may or may not be sensitizers themselves but greatly increase the sensitizing action of other dyes. These are known as super-sensitizers and are of considerable importance in facilitating the use of conventional sensitizing dyes. Whatever the dye used, the quantity required is always quite small.



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October 01, 2018
Gear teeth are designed so that the number of teeth on a gear is proportional to the radius of its pitch circle, and so that the pitch circles of meshing gears roll on each other without slipping. The speed ratio for a pair of meshing gears can be computed from ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear..

Two meshing gears transmit rotational motion.
The velocity v of the point of contact on the pitch circles is the same on both gears, and is given by
Where input gear A has radius rA and meshes with output gear B of radius rB, therefore,
Where NA is the number of teeth on the input gear and NB is the number of teeth on the output gear.
The mechanical advantage of a pair of meshing gears for which the input gear has NA teeth and the output gear has NBteeth is given by
This shows that if the output gear GB has more teeth than the input gear GA, then the gear train amplifies the input torque. And, if the output gear has fewer teeth than the input gear, then the gear train reduces the input torque.
If the output gear of a gear train rotates more slowly than the input gear, then the gear train is called a speed reducer. In this case, because the output gear must have more teeth than the input gear, the speed reducer will amplify the input torque.





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October 01, 2018
Understanding how things fly begins by learning about the Four Forces of Flight.
When an airplane flies, the wing is designed to provide enough Lift to overcome the airplane’s Weight, while the engine provides enough Thrust to overcome Drag and move the airplane forward. And the Thrust of a rocket engine overcomes the Weight of the object to move the rocket forward.
Increasing the weight of an aircraft affects the amount of lift needed. In turn, a larger wing would provide more lift, but that would increase the amount of drag and therefore increase the amount of thrust needed. The forces of flight are interconnected, and a change in one affects the others.
Discovery lands at NASA's Kennedy Space Center. The Space Shuttle flies in two very different environments: Earth's atmosphere and low Earth orbit. But the forces of flight act on it no matter where it is. The four forces of flight affect the Shuttle only when it’s in Earth’s atmosphere. When it’s in low Earth orbit, only weight and thrust act on it.
Credit: NASA

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