VTEC engine

VTEC (Variable Valve Timing and Lift Electronic Control) is a valvetrain system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles. This was the first system of its kind. Different types of variable valve timing and lift control systems have also been produced by other manufacturers (MIVEC from Mitsubishi, VVTL-i from Toyota, VarioCam Plus from Porsche, VVL from Nissan, etc). It was invented by Honda R&D engineer Ikuo Kajitani.It can be said that VTEC, the original Honda variable valve control system, originated from REV (Revolution-modulated valve control) introduced on the CBR400 in 1983 known as HYPER VTEC.In the regular four-stroke automobile engine, the intake and exhaust valves are actuated by lobes on a camshaft. The shape of the lobes determines the timing, lift and duration of each valve. Timing refers to an angle measurement of when a valve is opened or closed with respect to the piston position (TDC or BDC). Lift refers to how much the valve is opened. Duration refers to how long the valve is kept open. Due to the behavior of the working fluid (air and fuel mixture) before and after combustion, which have physical limitations on their flow, as well as their interaction with the ignition spark, the optimal valve timing, lift and duration settings under low RPM engine operations are very different from those under high RPM. Optimal low RPM valve timing, lift and duration settings would result in insufficient filling of the cylinder with fuel and air at high RPM, thus greatly limiting engine power output. Conversely, optimal high RPM valve timing, lift and duration settings would result in very rough low RPM operation and difficult idling. The ideal engine would have fully variable valve timing, lift and duration, in which the valves would always open at exactly the right point, lift high enough and stay open just the right amount of time for the engine speed in use.
VTEC was initially designed to increase the power output of an engine to 100 ps/liter or more while maintaining practicality for use in mass production vehicles. Some later variations of the system were designed solely to provide improvements in fuel efficiency, or increased power output as well as improved fuel efficiency.
In practice, a fully variable valve timing engine is difficult to design and implement.
The opposite approach to variable timing is to produce a camshaft which is better suited to high RPM operation. This approach means that the vehicle will run very poorly at low RPM (where most automobiles spend much of their time) and much better at high RPM. VTEC is the result of an effort to marry high RPM performance with low RPM stability.
Additionally, Japan has a tax on engine displacement, requiring Japanese auto manufacturers to make higher-performing engines with lower displacement. In cars such as the Toyota Supra and Nissan 300ZX, this was accomplished with a turbocharger. In the case of the Mazda RX-7 and RX-8, a rotary engine was used. VTEC serves as yet another method to derive very high specific output from lower displacement motors.Honda's VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of one cam lobe actuating each valve, there are two: one optimized for low-RPM stability & fuel efficiency; the other designed to maximize high-RPM power output. Switching between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low rpm ones. From this point on, the poppet valve opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load; the switch back from high to low rpm cams is set to occur at a lower engine speed than the up-switch, to avoid surging if the engine is asked to operate continuously at or around the switch-over point. The DOHC VTEC system has high and low lift cam lobe profiles on both the intake and exhaust valve camshafts.
The VTEC system was originally introduced as a DOHC system in the 1989 Honda Integra and Civic CRX SiR models sold in Japan and Europe, which used a 160 bhp (119 kW) variant of the B16A engine. The US market saw the first VTEC system with the introduction of the 1990 Acura NSX, which used a DOHC VTEC V6 with 270 hp. DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17 1.7 liter engine). And later in the 1994 Honda Prelude VTEC (H22 2.2 liter engine) and Honda Del Sol VTEC (B16 1.6 liter engine).
Honda has also continued to develop other varieties and today offers several varieties of VTEC: iVTEC, iVTEC Hybrid and VTEC in the NSX and some Japanese domestic market cars.i-VTEC (intelligent-VTEC) introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines. The technology first appeared on Honda's K-series four cylinder engine family in 2001 (2002 in the U.S.). Valve lift and duration are still limited to distinct low- and high-RPM profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. Phase changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to maximum advance at full throttle and low rpm. The effect is further optimization of torque output, especially at low and midrange RPM.
For the K-Series motors there are two different types of i-VTEC systems implemented. The first is for the performance motors like in the RSX Type S or the TSX and the other is for economy motors found in the CR-V or Accord. The performance i-VTEC system is basically the same as the DOHC VTEC system of the B16A's, both intake and exhaust have 3 cam lobes per cylinder. However the valvetrain has the added benefit of roller rockers and continuously variable intake cam timing. The economy i-VTEC is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. The two types of motor are easily distinguishable by the factory rated power output: the performance motors make around 200 hp or more in stock form and the economy motors do not make much more than 160 hp from the factory.
In 2004, Honda introduced an i-VTEC V6 (an update of the venerable J-series), but in this case, i-VTEC had nothing to do with cam phasing. Instead, i-VTEC referred to Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 mph) operation. The technology was originally introduced to the US on the Honda Odyssey Mini Van, and can now be found on the Honda Accord Hybrid and the 2006 Honda Pilot.
An additional version of i-VTEC was introduced on the 2006 Honda Civic's R-series four cylinder SOHC engines. This implementation uses the so-called "economy cams" on one of the two intake valves of each cylinder. The "economy cams" are designed to delay the closure of the intake valve they act upon, and are activated at low rpms and under light loads. When the "economy cams" are activated, one of the two intake valves in each cylinder closes well after the piston has started moving upwards in the compression stroke. That way, a part of the mixture that has entered the combustion chamber is forced out again, into the intake manifold. That way, the engine "emulates" a lower displacement than its actual one (its operation is also similar to an Atkinson cycle engine, with uneven compression and combustion strokes), which reduces fuel consumption and increases its efficiency. During the operation with the "economy cams", the (by-wire) throttle butterfly is kept fully open, in order to reduce pumping losses. According to Honda, this measure alone can reduce pumping losses by 16%. In higher rpms and under heavier loads, the engine switches back into its "normal cams", and it operates like a regular 4 stroke Otto cycle engine. This implementation of i-VTEC was initially introduced in the R18A1 engine found under the bonnet of the 8th generation Civic, with a displacement of 1,8lt and an output of 140Ps. Recently, another variant was released, the 2-litre R20A2 with an output of 150Ps, which powers the EUDM version of the all-new CRV
With the continued introduction of vastly different i-VTEC systems, one may assume that the term is now a catch-all for creative valve control technologies from Honda.

what is CDMA

Code division multiple access (CDMA) describes a communication channel access principle that employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code). In communications technology, there are only three domains that can allow multiplexing to be implemented for more efficient use of the available channel bandwidth and these domains are known as time, frequency and space. CDMA divides the access in signal space. By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency. CDMA is a form of "spread-spectrum" signaling, since the modulated coded signal has a much higher bandwidth than the data being communicated.
An analogy to the problem of multiple access is a room (channel) in which people wish to communicate with each other. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would speak different languages. People speaking the same language can understand each other, but not other people. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can understand each other.
CDMA is also the current name for the cellular technology originally known as IS-95. Developed by Qualcomm and enhanced by Ericsson, CDMA is characterized by high capacity and small cell radius.
CDMA also refers to digital cellular telephony systems that use this multiple access scheme, as pioneered by QUALCOMM, and W-CDMA by the International Telecommunication Union (ITU), which is used in GSM’s UMTS.
CDMA has been used in many communications and navigation systems, including the Global Positioning System and the OmniTRACS satellite system for transportation logistics.
Use in mobile telephony
The terms are used to refer to CDMA implementations. The original US standard defined by QUALCOMM was known as IS-95, where IS refers to an Interim Standard of the US Telecommunications Industry Association. IS-95 is often referred to as the second generation (2G) cellular, or as cdmaOne (the QUALCOMM brand name). CDMA has been submitted for approval as a mobile air interface standard to the International Telecommunication Union (ITU).
Whereas Global System for Mobile Communications (GSM) is a specification of an entire network infrastructure, CDMA relates only to the air interface — the radio portion of the technology. For example, GSM specifies an infrastructure based on internationally approved standard, while CDMA allows each operator to provide network features it finds suitable. On the air interface, the signalling suite (GSM: ISDN SS7) work has been progressing to harmonise these features.
After some revisions, IS-95 was superseded by the IS-2000 standard (CDMA2000). This standard was introduced to meet some of the criteria laid out in the IMT-2000 specification for third generation (3G) cellular. It is also called 1xRTT which means "1 times Radio Transmission Technology" because IS-2000 uses the same 1.25 MHz carrier shared channel as the original IS-95 standard. A related scheme, called 3xRTT, uses three 1.25 MHz carriers for a 3.75 MHz bandwidth that would allow higher data burst rates for an individual user, but the 3xRTT scheme has not been commercially deployed. More recently, QUALCOMM has led the creation of a new CDMA-based technology called Evolution-Data Optimized (1xEV-DO, or IS-856), which provides the higher packet data transmission rates required by IMT-2000 and desired by wireless network operators.
This CDMA system is frequently confused with a similar but incompatible technology called Wideband Code Division Multiple Access (W-CDMA) which is the basis of the W-CDMA air interface. The W-CDMA air interface is used in the global 3G standard UMTS and the Japanese 3G standard FOMA, by NTT DoCoMo and Vodafone; however, the CDMA family of US national standards (including cdmaOne and CDMA2000) are not compatible with the W-CDMA family of ITU standards.
Another important application of code division multiplexing — predating and distinct from CDMA — is the Global Positioning System (GPS).
The QUALCOMM CDMA system includes very accurate time signals (usually referenced to a GPS receiver in the cell base station), so cell phone CDMA-based clocks are an increasingly popular type of radio clock for use in computer networks. The main advantage of using CDMA cell phone signals for reference clock purposes is that they work better inside buildings, thus often eliminating the need to mount a GPS antenna outside a building

the Investment

Investment or investing is a term with several closely-related meanings in business management, finance and economics, related to saving or deferring consumption. An asset is usually purchased, or equivalently a deposit is made in a bank, in hopes of getting a future return or interest from it. The word originates in the Latin "vestis", meaning garment, and refers to the act of putting things (money or other claims to resources) into others' pockets.The term "investment" is used differently in economics and in finance. Economists refer to a real investment (such as a machine or a house), while financial economists refer to a financial asset, such as money that is put into a bank or the market, which may then be used to buy a real asset.
The investment decision (also known as capital budgeting) is one of the fundamental decisions of business management: managers determine the assets that the business enterprise obtains. These assets may be physical (such as buildings or machinery), intangible (such as patents, software, goodwill), or financial (see below). The manager must assess whether the net present value of the investment to the enterprise is positive; the net present value is calculated using the enterprise's marginal cost of capital.
A business might invest with the goal of making profit. These are called marketable securities or passive investment. It might also invest with the goal of controlling or influencing the operation of the second company, the investee. These are called intercorporate, long-term and strategic investments. Hence, a company can have none, some or total control over the investee 's strategic, operating, investing and financing decisions. One can control a company by owning over 50% ownership, or have the ability to elect a majority of the Board of Directors.In economics, investment is the production per unit time of goods which are not consumed but are to be used for future production. Examples include tangibles (such as building a railroad or factory) and intangibles (such as a year of schooling or on-the-job training). In measures of national income and output, gross investment I is also a component of Gross domestic product (GDP), given in the formula GDP = C + I + G + NX. I is divided into non-residential investment (such as factories) and residential investment (new houses). "Net" investment deducts depreciation from gross investment. It is the value of the net increase in the capital stock per year.
Investment, as production over a period of time ("per year"), is not capital. The time dimension of investment makes it a flow. By contrast, capital is a stock, that is, an accumulation measurable at a point in time (say December 31st).
Investment is often modeled as a function of income and interest rates, given by the relation I = f(Y, r). An increase in income encourages higher investment, whereas a higher interest rate may discourage investment as it becomes more costly to borrow money. Even if a firm chooses to use its own funds in an investment, the interest rate represents an opportunity cost of investing those funds rather than loaning them out for interest.In finance, investment is buying securities or other monetary or paper (financial) assets in the money markets or capital markets, or in fairly liquid real assets, such as gold, real estate, or collectibles. Valuation is the method for assessing whether a potential investment is worth its price.
Types of financial investments include shares, other equity investment, and bonds (including bonds denominated in foreign currencies). These financial assets are then expected to provide income or positive future cash flows, and may increase or decrease in value giving the investor capital gains or losses.
Trades in contingent claims or derivative securities do not necessarily have future positive expected cash flows, and so are not considered assets, or strictly speaking, securities or investments. Nevertheless, since their cash flows are closely related to (or derived from) those of specific securities, they are often studied as or treated as investments.
Investments are often made indirectly through intermediaries, such as banks, mutual funds, pension funds, insurance companies, collective investment schemes, and investment clubs. Though their legal and procedural details differ, an intermediary generally makes an investment using money from many individuals, each of whom receives a claim on the intermediary.Commercial real estate is the owning of a small building or large warehouse a company rents from so that it can conduct its business. Due to the higher risk of Commercial real estate, lending rates of banks and other lenders are lower and often fall in the range of 50-70%.The most common form of real estate investment as it includes the property purchased as peoples houses. In many cases the Buyer does not have the full purchase price for a property and must engage a lender such as a Bank, Finance company or Private Lender. Different countries have their individual normal lending levels, but usually they will fall into the range of 70-90% of the purchase price. Against other types of real estate, residential real estate is the least risky.In real estate, investment is money used to purchase property for the sole purpose of holding or leasing for income and where there is an element of capital risk. Unlike other economic or financial investment, real estate is purchased. The seller is also called a Vendor and normally the purchaser is called a Buyer.Within personal finance, money used to purchase shares, put in a collective investment scheme or used to buy any asset where there is an element of capital risk is deemed an investment. Saving within personal finance refers to money put aside, normally on a regular basis. This distinction is important, as investment risk can cause a capital loss when an investment is realized, unlike saving where the more limited risk is cash devaluing due to inflation.
In many instances the terms saving and investment are used interchangeably, which confuses this distinction. For example many deposit accounts are labeled as investment accounts by banks for marketing purposes. Whether an asset is a saving(s) or an investment depends on where the money is invested: if it is cash then it is savings, if its value can fluctuate then it is investment.

The Account

In accountancy, an account is a label used for recording and reporting a quantity of almost anything. Most often it is a record of an amount of money owned or owed by or to a particular person or entity, or allocated to a particular purpose. It may represent amounts of money that have actually changed hands, or it may represent an estimate of the values of assets.Types of Accounts.

1. Asset : represent the different types of economic resources owned by a business, common examples of Asset accounts are cash, cash in bank, building, inventory, prepaid rent, goodwill, accounts receivable.
2. Liability : represent the different types of economic obligations by a business, such as accounts payable, bank loan, bonds payable, accrued interest.
3. Equity: represent the residual equity of a business (after deducting from Assets all the liabilities) including Retained Earnings and Appropriations.
4. Revenue or Income : represent the company's gross earnings and common examples include Sales, Service revenue and Interest Income.
5. Expense: represent the company's expenditures to enable itself to operate. Common examples are electricity and water, rentals, depreciation, doubtful accounts, interest, insurance.
6. Contra-accounts: from the term contra, meaning to deduct, the value of which are opposite the 5 above mentioned types of accounts. For instance, a contra-asset account is Accumulated depreciation. This label represent deductions to a relatively permanent asset like Building.

Circuit breaker

A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.






Operation






Magnetic circuit breakers are implemented using a solenoid (electromagnet) whose pulling force increases with the current. The circuit breaker's contacts are held closed by a latch and, as the current in the solenoid increases beyond the rating of the circuit breaker, the solenoid's pull releases the latch which then allows the contacts to open by spring action. Some types of magnetic breakers incorporate a hydraulic time delay feature wherein the solenoid core is located in a tube containing a viscous fluid. The core is restrained by a spring until the current exceeds the breaker rating. During an overload, the solenoid pulls the core through the fluid to close the magnetic circuit, which then provides sufficient force to release the latch. The delay permits brief current surges beyond normal running current for motor starting, energizing equipment, etc. Short circuit currents provide sufficient solenoid force to release the latch regardless of core position thus bypassing the delay feature. Ambient temperature affects the time delay but does not affect the current rating of a magnetic breaker.
Thermal breakers use a bimetallic strip, which heats and bends with increased current, and is similarly arranged to release the latch. This type is commonly used with motor control circuits. Thermal breakers often have a compensation element to reduce the effect of ambient temperature on the device rating.
Thermomagnetic circuit breakers, which are the type found in most distribution boards, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term overcurrent conditions.
Circuit breakers for larger currents are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism.
Under short-circuit conditions, a current many times greater than normal can flow (see maximum prospective short circuit current). When electrical contacts open to interrupt a large current, there is a tendency for an arc to form between the opened contacts, which would allow the flow of current to continue. Therefore, circuit breakers must incorporate various features to divide and extinguish the arc. In air-insulated and miniature breakers an arc chute structure consisting (often) of metal plates or ceramic ridges cools the arc, and blowout coils deflect the arc into the arc chute. Larger circuit breakers such as those used in electrical power distribution may use vacuum, an inert gas such as sulfur hexafluoride or have contacts immersed in oil to suppress the arc.
The maximum short-circuit current that a breaker can interrupt is determined by testing. Application of a breaker in a circuit with a prospective short-circuit current higher than the breaker's interrupting capacity rating may result in failure of the breaker to safely interrupt a fault. In a worst-case scenario the breaker may successfully interrupt the fault, only to explode when reset, injuring the technician.
Small circuit breakers are either installed directly in equipment, or are arranged in a breaker panel. Power circuit breakers are built into switchgear cabinets. High-voltage breakers may be free-standing outdoor equipment or a component of a gas-insulated switchgear line-up.


Domestic circuit breakers

The 10 ampere DIN rail mounted thermal-magnetic miniature circuit breaker is the most common style in modern domestic consumer units and commercial electrical distribution boards throughout Europe. The design includes the following components:
1:Actuator lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the on position. This is sometimes referred to as "free trip" or "positive trip" operation.
2:Actuator mechanism - forces the contacts together or apart.
3:Contacts - Allow current to flow when touching and break the flow of current when moved apart.
4:Terminals
5:Bimetallic strip
6:Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.
7:Solenoid
8:Arc divider / extinguisher

Turbine

A turbine is a rotary engine that extracts energy from a fluid flow. Claude Burdin (1788-1873) coined the term from the Latin turbo, or vortex during an 1828 engineering competition. Benoit Fourneyron (1802-1867), a student of Claude Burdin, built the first practical water turbine.

The simplest turbines have one moving part, a rotor assembly, which is a shaft with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they rotate and impart energy to the rotor. Early turbine examples are windmills and water wheels.

Gas, steam, and water turbines usually have a casing around the blades that focuses and controls the fluid. The casing and blades may have variable geometry that allows efficient operation for a range of fluid-flow conditions.

A device similar to a turbine but operating in reverse is a compressor or pump. The axial compressor in many gas turbine engines is a common example.

Electric motor

An electric motor converts electrical energy into mechanical energy. The reverse process, that of converting mechanical energy into electrical energy, is accomplished by a generator or dynamo. Traction motors used on locomotives often perform both tasks if the locomotive is equipped with dynamic brakes. Electric motors are found in household appliances such as fans, refrigerators, washing machines, pool pumps, floor vacuums, and fan-forced ovens.
Most electric motors work by electromagnetism, but motors based on other electromechanical phenomena, such as electrostatic forces and the piezoelectric effect, also exist. The fundamental principle upon which electromagnetic motors are based is that there is a mechanical force on any current-carrying wire contained within a magnetic field. The force is described by the Lorentz force law and is perpendicular to both the wire and the magnetic field. Most magnetic motors are rotary, but linear motors also exist. In a rotary motor, the rotating part (usually on the inside) is called the rotor, and the stationary part is called the stator. The rotor rotates because the wires and magnetic field are arranged so that a torque is developed about the rotor's axis. The motor contains electromagnets that are wound on a frame. Though this frame is often called the armature, that term is often erroneously applied. Correctly, the armature is that part of the motor across which the input voltage is supplied. Depending upon the design of the machine, either the rotor or the stator can serve as the armature.