VoLTE technology in JIO; What is VoLTE?

In recent days JIO has generated lot of buzz which offers free calling for lifetime and free internet up to December. There is also new technology associated with JIO is VoLTE. Mobile phone manufacturers are selling phones with VoLTE enabled technology. Now there is curiosity what is VoLTE? and how it is different?

In this below article we will learn what is VoLTE technology all about?:-

VoLTE:-

There is new technology in field of data services. VoLTE is known as Voice over Long-Term Evolution. It is used for providing a uniform format of voice traffic on LTE and other systems including CSFB (Circuit Switched Fall Back) and SV-LTE(Simultaneous Voice Long term evolution). This technology is used for better voice call quality. VoLTE uses 4G technology and it is based on packet switching on the other hand 2G and 3G networks uses circuit based switch.

Now when we make a call using 2G and 3G then there is bandwidth assigned to that call this will not allow to terminate until call ends. On the other hand in VoLTE voice calls are divided into packets and are sent on whole data pipeline which will then get reconstructed at receiving end. As calling is done over whole data pipeline which means better calling using VoLTE technology.

VoLTE is designed for standardizing the system for transferring Voice traffic over Long term evolution.

LTE was basically an IP cellular system used for carrying data. Operators would be able to carry voice either by reverting to 2G / 3G Systems. Operators can use VoIP in one form or another.

LTE will lead disintegration and mismatch not allowing all phones to communicate with each other which will reduce the voice traffic. SMS services are still widely used, often proving a means of set-up for other applications.

Even though revenue from voice calls and SMS is falling, a format for voice over LTE and messaging, it was as necessary to have a viable and standardized scheme to provide the voice and SMS services to protect this revenue.

LTE Voice Options:-

There are following options for Long term Evolution voicing:-

(i)             CSFB known as Circuit switched Fall back

(ii)            SV-LTE Known as Simultaneous Voice LTE

(iii)           VoLGA known as Voice over LTE via GAN

(iv)          One Voice / later called Voice over LTE, VoLTE

Let’s discuss about these:-

(i)             CSFB:- This service has been standardized under 3GPP Specifications. CSFB uses different types of processes and network elements to enable the circuit to fall back to 2G/3G connection before a circuit switched call is initiated. The description also allows for SMS to be carried as this is important for very many set-up procedures for cellular telecommunications. To achieve this handset uses an interface known as SGs which allows messages to be sent over an LTE channel.

(ii)            SV-LTE:   This service allows packet switched LTE services to run concurrently with a circuit switched voice service. This facility provides the facilities of CSFB at the same time as running a packet switched data service. There is a disadvantage associated with this service is that, it requires two radios to run at the same time within the handset which has a serious impact on battery life.

(iii)           VoLGA:- This service was based on the current 3GPP Generic Access Network (GAN) standard, and the aim was to allow LTE users to obtain a steady set of voice, SMS services as they shift between GSM, UMTS and LTE access networks. For mobile operators, the aim of VoLGA was to provide a low-cost and low-risk approach for bringing their primary revenue generating services onto the new LTE network deployments.

(iv)          VoLTE:   This scheme for providing voice over an LTE system develops IMS The IP Multimedia Subsystem,  IMS is a framework for delivering Internet Protocol. It enables a variety of services to be run flawlessly rather than having several different applications operating simultaneously), which enables it to become part of a rich media solution. It was the option chosen by the GSMA for use on LTE and is the standardized method for providing SMS and voice over LTE.

Voice over LTE

When concept of SMS and voice System over LTE using IMS was introduced than it was opposed by many telecom operators as it was complex system involving IMS. It was observed that it is not only complex but also it is far too expensive and burdensome to introduce and maintain the same.

One Voice profile for Voice over LTE was developed by association between over 40 operators. In 2010 GSMA declared that they were supporting the One Voice solution to provide Voice over LTE. To achieve a workable system, a cut down variant of IMS was used. It was felt that this would be acceptable to operators while still providing the functionality required.

The VoLTE system is based on the IMS MMTel concepts that were previously in existence. It has been specified in the GSMA profile IR 92.

VoLTE IP versions

After update from IPv4 to IPv6 version ,VoLTE devices are needed to operate in dual mode which will cater both IPv4 and IPv6.

One of the issues with voice over IP type calls is the overhead resulting from the IP header. To overcome this issue VoLTE requires that IP header compression is used along with RoHC (Robust Header Compression) protocol for voice data packet headers.

Methods for reducing Harmonics in System

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Methods for Reducing Harmonics in Electrical Systems

Harmonics are one of the biggest challenges in modern electrical systems, especially with the growing use of non-linear loads such as Variable Frequency Drives (VFDs), rectifiers, and electronic devices. Excessive harmonics can lead to equipment overheating, reduced efficiency, nuisance tripping, and overall poor power quality.

Fortunately, several methods exist to reduce harmonics and improve system reliability. Let’s explore the most effective solutions.

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1. DC Choke

• Application: Commonly used in VFDs (a major source of harmonics).
• Working Principle: A DC choke is an inductor in series with the DC link of the semiconductor bridge circuit.
• Effect:
• Reduces 5th and 7th order harmonics
• Improves current waveform smoothness
• Comparable to AC-side line reactors (though THD reduction is slightly less).

✅ Key Point: DC chokes are simple, cost-effective, and widely used in drives.

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2. Reducing Harmonics at Loads and Source

Since VFDs and non-linear equipment are major harmonic sources, minimizing harmonics directly at the load/source is often the most effective strategy.

Example – Transformer Phase Shifting

• Installing a Delta-Star Transformer in parallel with a Delta-Delta Transformer allows conversion of two synchronized 6-pulse VFDs into a 12-pulse VFD application.
• Why effective?
• Phase shift changes from 60° (6-pulse) to 30° (12-pulse).
• Reduces 5th and 7th harmonics.
• Delta connection blocks zero-sequence harmonics → eliminating triple harmonics.

✅ Key Point: Transformer configuration plays a big role in harmonic mitigation.

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3. Using Filters

Filters are one of the most common methods to control harmonics. They are broadly divided into passive and active filters.

(a) Passive Filters

• Made of inductors, capacitors, and transformers.
• Work by blocking or diverting harmonics to ground.
• Designed for specific harmonic orders.

Advantages:

• Simple and cost-effective.
• Widely used in AC drives (line reactors, transformers).

Limitations:

• Effectiveness reduces when harmonic spectrum changes with load variation.
• Can cause resonance issues if not designed properly.

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(b) Active Filters

• Also called power line conditioners.
• Work by sensing harmonic currents and injecting a counter waveform to cancel them out.
• Installed in parallel with the load.

How They Work:

1. Current Transducers measure the load current.
2. Fundamental frequency component is removed.
3. The remaining harmonic waveform is inverted and injected back via IGBTs (PWM switching).
4. Harmonics are cancelled → improving both power factor and voltage waveform.

Key Components:

• Power semiconductors (IGBTs, PWM control)
• DC link capacitors & bus bars
• Internal filters & protective fuses

Scalability: If harmonic levels exceed one filter’s rating, multiple active filters can be installed in parallel.

✅ Key Point: Active filters are more flexible and effective than passive filters, especially for varying load conditions.

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Quick Comparison

Method	Best For	Harmonic Orders Reduced	Cost & Complexity
DC Choke	VFDs	5th, 7th	Low
Transformer Shift	Industrial plants (multi-VFDs)	5th, 7th, triple	Medium
Passive Filter	Fixed load harmonics	Specific orders	Low–Medium
Active Filter	Variable loads, precise mitigation	Wide range (dynamic)	Higher

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Conclusion

Harmonics cannot be eliminated entirely, but they can be controlled and minimized with the right mix of DC chokes, transformer configurations, and filters. For most industrial setups, a combination approach works best:

• DC chokes for VFDs
• Transformer phase-shifting for multiple drives
• Filters (passive or active) for overall system compliance with IEEE/IEC harmonic limits.

By applying these solutions, power quality improves, equipment life extends, and energy efficiency increases.

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Harmonics and its effects on electrical systems

Harmonics in Electrical Systems: Causes, Effects, and Impact on Equipment

What Are Harmonics?

Harmonics are unwanted voltages and currents in electrical systems that distort the fundamental waveform (50 Hz in India). They arise due to non-linear loads that draw current in abrupt pulses rather than smooth sinusoidal waves.

In simple terms, harmonics are like pollution in electricity—they degrade power quality without necessarily affecting power availability.

Classification of Harmonics

Harmonics are integer multiples of the fundamental frequency (50 Hz):

• 2nd harmonic (100 Hz)

• 3rd harmonic (150 Hz)

• 4th harmonic (200 Hz)

• … up to the 11th harmonic (550 Hz) and beyond.

Depending on their order:

• Negative Sequence Currents: 2nd, 5th, 8th, 11th

• Zero Sequence Currents: 3rd, 6th, 9th

• Positive Sequence Currents: 4th, 7th, 10th

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Why Are Harmonics Increasing?

The rise in harmonics is directly linked to the increasing use of electronic and power conversion devices.

Major Sources of Harmonics

1. Non-linear loads such as Variable Frequency Drives (VFDs), UPS, SMPS, rectifiers, and inverters.

2. Arcing devices (arc furnaces, welding machines).

3. Ferromagnetic devices (transformers operating near saturation).

4. Electronic switching power converters.

5. Household and commercial appliances with embedded power electronics.

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Effects of Harmonics on Electrical Systems

General System Effects

• Overheating of electrical equipment.

• Reduction in equipment life.

• Malfunctioning and premature failure of devices.

• Higher system losses and reduced efficiency.

• Interference in communication systems.

• Nuisance tripping of circuit breakers and fuses.

• Motor vibrations and noise.

• Computer screen flickering and data errors.

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Harmonics and Power Factor

Traditionally, power factor (PF) is:

$$PF = \frac{\text{Real Power (kW)}}{\text{Apparent Power (kVA)}}$$

However, with harmonics, we must consider Distortion Power Factor (DPF):

$$DPF = \frac{1}{\sqrt{1 + THDi^2 + THDv^2}}$$

Where:

• THDi = Total Harmonic Distortion in Current

• THDv = Total Harmonic Distortion in Voltage

Thus, the Total Power Factor = Displacement PF × Distortion PF, which means PF will never be unity in the presence of harmonics, even with capacitor banks.

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Effects of Harmonics on Different Equipment

1. Transformers

• Increased eddy current losses.

• Additional heating in windings.

• Higher skin effect losses.

• Premature insulation failure.

2. Motors

• Increased hysteresis losses (∝ frequency).

• Eddy current losses (∝ frequency²).

• High rotor & stator losses.

• Tooth pulsations leading to vibration.

• Overheating and shortened lifespan.

3. Cables

• Higher proximity and skin effects.

• Increased resistance and power losses.

• Overheating leading to insulation degradation.

• Derating of cable capacity.

• Higher neutral currents causing imbalance.

4. Capacitor Banks

• Resonance with 7th harmonic (risk of overvoltage).

• Reduced capacitive reactance.

• Premature failure due to overheating.

• Increased KVA demand and electricity bills.

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Why Should We Care About Harmonics?

• Reduced efficiency → Higher operating costs.

• Premature equipment failure → Expensive replacements.

• Poor power factor → Higher utility penalties.

• System instability → Risk of downtime.

When harmonics are present in a system, they increase KVA demand and ultimately raise electricity bills. Here’s why:

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1. Relationship Between kW, kVA, and Power Factor

• kW (kilowatt) = Useful (real) power that does actual work.

• kVA (kilovolt-ampere) = Total apparent power supplied.

• Power Factor (PF) = kW ÷ kVA.

When harmonics distort the waveform, they:

• Increase the RMS current in the system.

• Cause a drop in power factor (due to distortion PF).

• This means: For the same useful power (kW), the required kVA (apparent power) increases.

👉 Utilities often charge based on maximum kVA demand (not just kW). So, higher kVA = higher demand charges.

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2. How Harmonics Increase System Losses

• Harmonics introduce extra current components (2nd, 3rd, 5th, etc.) that do not contribute to useful power.

• These harmonic currents cause:

  • I²R losses in cables and transformers.

  • Higher eddy current and hysteresis losses in transformers/motors.

  • Extra heating and derating of equipment.

👉 This wasted energy still flows through the meter, showing up as increased kWh consumption.

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3. Capacitor Bank Issue

Many plants use capacitor banks to improve PF. But with harmonics:

• Capacitors may resonate at certain harmonic frequencies (e.g., 5th, 7th).

• This amplifies harmonic currents instead of compensating them.

• The plant ends up drawing more reactive power from the grid, worsening kVA demand.

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4. Direct Impact on Electricity Bill

1. Higher kVA demand charges

   • Utilities charge based on peak demand (kVA).

   • Harmonics inflate apparent power → demand charges increase.

2. Higher energy (kWh) consumption

   • Extra losses caused by harmonics (heating, eddy currents, neutral currents) are billed as real energy consumed.

3. Penalty for low power factor

• Some utilities impose penalties if PF drops below a threshold (say 0.9).

• Harmonics reduce PF even if displacement PF is corrected.

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✅ Example:

• A factory needs 500 kW of real power.

• Without harmonics: PF ≈ 0.95 → kVA = 526.

• With harmonics: PF drops to 0.8 → kVA = 625.

That’s nearly 100 kVA extra demand for the same work → more demand charges + higher losses.

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⚡ In short:
Harmonics → Higher RMS currents → Higher apparent power (kVA) → Higher demand charges + more losses → Bigger electricity bills.

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✅ Next Step: For practical methods to mitigate harmonics, check out Methods for Reducing Harmonics in System.

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⚡ Final Note: Harmonics are unavoidable in modern power systems, but their impact can be minimized through proper design, filtering, and load management.

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Electricity from Pototes and Other Fruits and vegetables

Electricity from Potatoes and Fruits: Science Behind the Experiment

Generating electricity from simple household items like potatoes, lemons, or apples may sound like a classroom trick, but the concept is deeply rooted in electrochemistry. The principle is the same as that used in early batteries: when two dissimilar metals are placed in an electrolytic medium, an electron flow (electric current) is created.

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Basic Principle

When metals such as zinc and copper are inserted into an electrolyte (like potato juice or lemon juice), a chemical reaction occurs. The electrolyte enables ions to move between the electrodes. The difference in reactivity of the two metals creates a potential difference, which drives electron flow through an external circuit.

• Zinc electrode → acts as the anode (oxidation occurs).

• Copper electrode → acts as the cathode (reduction occurs).

• Electrolyte (potato/fruit juice) → provides the ionic medium.

This setup is essentially a Galvanic Cell—a miniature battery.

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Potato Power Experiment

Materials Required

• 8 medium-sized raw potatoes

• Zinc electrode (galvanized nails)

• Copper electrode (coins or wires)

• Connecting wires

• 1 LED light

Steps

1. Insert one zinc and one copper electrode into each potato.

2. Connect the potatoes in series (zinc of one potato to copper of the next).

3. After connecting all 8 potatoes, attach free ends of the circuit to an LED.

4. The LED will glow, powered by DC voltage generated from potatoes.

👉 Each potato generates around 1.2 volts. Since a red LED typically requires ~2V, multiple potatoes are connected in series to achieve sufficient voltage.

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Why Lemons and Other Fruits Work Better

Lemons, oranges, and apples can also be used because their juices are more acidic than potato starch. The stronger acidity accelerates the electrochemical reaction, giving slightly higher voltage and current output compared to potatoes.

• Lemon: ~0.9–1.0 V per fruit

• Potato: ~1.2 V per potato

Thus, you may need fewer lemons to light up the same LED.

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Electricity from Boiled Potatoes

Recent studies have shown that boiled potatoes produce nearly 10 times more electricity than raw ones. Why?

• Boiling reduces the internal resistance of the potato.

• The softened tissue allows ions to move more freely, enhancing conductivity.

• Cutting potatoes into smaller pieces further increases surface area, boosting efficiency.

In fact, boiled potatoes have been demonstrated to power small bulbs or devices for weeks under optimized conditions.

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Applications and Limitations

Applications

• Useful for educational demonstrations of electrochemistry.

• Can power low-energy devices like LEDs or small digital clocks.

• Promotes awareness of renewable and alternative energy sources.

Limitations

• Voltage and current levels are very low (not practical for large-scale use).

• Electrodes corrode over time, reducing efficiency.

• Potatoes and fruits decay, limiting lifespan of the "battery."

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Fun Facts

• The Potato Clock is a popular science project for schoolchildren worldwide.

• Similar principles are used in bio-batteries, which use organic material for power generation.

• Researchers are exploring food-based bio-electrochemical cells for emergency power in remote areas.

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Conclusion

The potato battery experiment is more than just a classroom trick. It’s a simplified model of electrochemical energy conversion, demonstrating how ordinary food items can act as electrolytes to generate electricity. While not practical for powering homes, it remains a fascinating example of science in everyday life.

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Disclaimer

The information provided in this article is intended for educational purposes only. Potato and fruit batteries produce very low voltages and currents, suitable only for demonstrations and experiments. They are not viable for household or industrial power generation. Readers are advised to exercise caution while handling electrodes and wires during experiments.

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Synchronous Generators Prime movers; Steam turbine; Hydraulic turbine & diesel engines

Synchronous machines construction depends upon type of prime mover used in machines. There are following types of prime movers used in power generation:-

1.       Steam turbines

2.       Hydraulic Turbines

3.       Diesel Engines

Let’s discuss them :-

1.     Steam turbine:-

These types of synchronous machines have high speed.  Generators driven by steam turbine are also called Turbogenerators. Maximum speed of Turbogenerators is 3000 RPM as per formula

Frequency= PN/ 120;

Where P is no. of poles

N is no. of revolutions

In 2 Pole machine at 50 HZ frequency Speed of Turbogenerator comes out to be= 50X120/ 2= 3000 RPM

With Such high speed lower value of armature diameter is to be designed. Lower diameter is selected to limit the centrifugal forces which have very much influence on the generator design.

Peripheral Speed of a Machine is given by formula as below:-

Peripheral Speed(V)= πDn  m/Sec

Where D is diameter of rotor in meters

n=speed of rotor in revolutions per second

As we have seen from above formula that Peripheral Speed increases with increase in diameter as both are directly proportion to each other, With increase in diameter centrifugal forces increases. So diameter should be kept low.

Due to this high speed diameter of 2 pole machine is limited to 1.2 meter which will give peripheral speed of about 175 m/s.

Also for turbogenerators cylindrical rotor construction is to be used instead of salient pole as in Salient pole construction is impractical in turbogenerators due to high mechanical forces.

In these alternators efficiency is very high. Turbo-generators are available upto rating of 1000 MW.

2.     Hydraulic Turbines:-

Power plants using hydraulic turbines are Hydro Power plants these power plants uses Synchronous generators driven by Hydraulic turbines. Hydraulic turbines are driven by water heads. There are 3 types of hydraulic turbines due to different levels of water head availability.

Types of Hydraulic turbine used according to head height are as below:-

(i)                  For Water heads of 400 Meter and above- Pelton Wheel design to be used

(ii)                For water heads upto 380 meter – Francis turbine design to be used

(iii)               For water heads upto 50 meter- Kaplan turbine design to be used

As water heads not so much high so speed of turbine is low varies from 50 to 500 rpm. So get such low rpm salient pole alternators are used for the same. No. of poles in these generators are 12 onwards.

Also further Pelton type turbine design can be Horizontal or vertical shaft type. Usually Horizontal Shaft design is more commonly used.  For high power low speed synchronous generators are usually installed for low water heads power plants are generally built with vertical shaft.

There are following fundamental types for vertical shaft Hydro generators:-

(i)                 Suspended Type:-

In this type thrust bearing is at upper bracket above alternator rotor

(ii)               Umbrella Type:-

In this type bearing is mounted on lower bracket on the turbine cover, Mostly umbrella type construction is used to reduce generator weight and height of power plant. As in suspended type where bearing is used on upper bracket it has to be bigger in size as it has to withstand both generator and turbine load, also it has to withstand water reaction. This will leads to higher generator weight and height of power plant.

These type of generators have rating upto 750 MW.

3.       Diesel Engines:-

These are most widely used in small commercial and industrial establishments also known as Diesel generators. They are usually of small rating. These are horizontal type,  Since these are slow speed machines so salient pole construction is used for the same. Torque generated during its operation is non-uniform so it makes the synchronous generator sensitive to torque variations.

Why Power isn't generated at Higher Frequency i.e. greater than 50/ 60 HZ??

There is more often a question arises while you are dealing with electrical systems.
As you know that for alternators (Synchronous generators)
Frequency=  No. of Pole X Speed of Machine

                               120
So increasing the frequency of power generation you have to either increase the no. of poles or increase the speed of alternator.
Now if you increase no. of poles than diameter of machine will increase considerably to accommodate increased no. of poles. Also if machine diameter is increased to accommodate no. of poles then you can't rotate the machine at higher speed as centrifugal forces and vibration forces will be very high. Mechanical strength requirements of machines will also be very high.

Now for increasing speed of alternator you have to provide higher input which will leads to very high maintenance as deterioration happens at such a higher input. So alternator should be mechanically very strong .

Why Armature is place on Stator in Synchronous machines

Why Armature Winding is Placed on Stator and Field Winding on Rotor in Synchronous Machines?

In synchronous machines—both synchronous generators (alternators) and synchronous motors—the armature winding is always placed on the stator while the field winding is mounted on the rotor. This construction is not accidental; it offers clear technical and economic advantages.

Let us analyze these reasons step by step with practical examples.

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1. Better Economy of Construction

If the armature winding were placed on the rotor, slip rings would need to carry very high currents at high voltages, making the system bulky, costly, and inefficient.

Example:
Consider a 3-phase, star-connected, 500 MVA, 11 kV synchronous generator:

• Line current,

  $$I = \frac{500 \times 10^6}{\sqrt{3} \times 11 \times 10^3} = 26,244 \text{ A}$$

If this huge current were carried through slip rings, we would require 3 slip rings rated for 26.2 kA each, insulated for a line voltage of 6.35 kV. Additionally, a fourth slip ring would be needed to connect the star point to ground through a neutral resistance.

On the other hand, if the field winding is placed on the rotor, it only handles the DC excitation current at relatively low voltage (usually 100–500 V). Even for large machines, this current rarely exceeds a few thousand amperes. For instance:

• For a 2 MW field winding at 500 V,

  $$I_f = \frac{2000}{0.5} = 4000 \text{ A}$$

Here, only two slip rings are needed, insulated for 500 V only, which is far more economical and practical.

👉 Conclusion: Placing the field winding on the rotor reduces cost, complexity, and insulation requirements.

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2. Lower Insulation Requirements

When the armature winding is on the stator, its terminals are directly connected to the external power system without passing through slip rings.

• Slip rings now carry only low-voltage DC excitation instead of high-voltage AC armature current.

• This makes insulation simpler and allows construction of large synchronous machines up to 33 kV and beyond.

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3. Reduced Brush and Slip Ring Losses

If the armature were on the rotor, four large brushes would be needed to carry massive AC currents. This would increase:

• Contact losses

• Maintenance costs

• Heat generation

By placing the field winding on the rotor, only two brushes are required for the excitation system, handling far smaller currents. This results in lower losses and longer service life.

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4. Higher Output Power Capability

Since the rotor carries only the field winding, it is lighter and experiences less centrifugal stress. This enables:

• Higher operating speeds (higher RPM)

• More compact design

• Higher output power for the same machine size

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5. Mechanical and Thermal Advantages

• Armature winding on stator allows use of larger conductors and heavier insulation, since the stator is stationary.

• Cooling systems such as water jackets or hydrogen cooling can be installed more effectively on the stator than on a rotating rotor.

• This ensures better heat dissipation and higher reliability.

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6. Stronger Armature Tooth Strength

In high-current machines, slots must accommodate large amounts of copper. Cutting deep slots in a rotor weakens rotor teeth, making them prone to mechanical stress and vibration.

By placing the armature on the stator:

• Stator teeth can be made deeper and stronger,

• Resulting in reduced vibration, lower noise, and better mechanical stability.

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7. Lower Rotor Weight and Lighter Bearings

Since the rotor carries only the field winding (low copper content and simple insulation):

• The rotor becomes lighter,

• Bearings carry less load,

• Leading to cheaper construction and longer bearing life due to reduced wear and tear.

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Final Summary

Aspect	Armature on Rotor	Armature on Stator
Slip Ring Current	Very High (AC)	Low (DC excitation only)
Slip Ring Insulation	High (kV range)	Low (few hundred volts)
Losses	High (brush + slip ring losses)	Low
Rotor Weight	Very Heavy	Lighter
Cooling	Difficult	Easier
Mechanical Stress	High	Low
Output Capability	Limited	Higher

👉 Therefore, for technical, economic, and operational reasons, the armature winding is always placed on the stator, and the field winding is placed on the rotor in synchronous machines.

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Disclaimer

This article is intended for educational purposes and provides a general technical explanation of synchronous machine design. Practical design considerations may vary depending on machine size, application, and manufacturer-specific standards. Readers should consult standard references (e.g., IEEE, IEC) and manufacturer guidelines for detailed engineering applications.

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