CrazyEngineers Forum

Concepts of enthalpy and internal energy
Voltage comparator with variable voltage input. How?!
Turbine Supervisory Instruments
Bridge engineering books
Bridge Design Books
Hi active brainzz...!!!
Technovision'11
SolidWorks - From Dream to Design
SEA's Virtual Internship Program, February 7 – April 29, 2011
First Day At College : Share Your Story
guide needed for fina year project-IT
DC linear solenoid
Facebook Connection Enabled : Help Us Test It
iPad 2 Coming In Feb First Week- Kevin Rose
Micromax EG333 Tata Photon+ Phone Review | Price In India

Concepts of enthalpy and internal energy

Posted: 08 Jan 2011 01:10 PM PST

Hi I m a mechanical engineer and I was going through my books of thermodynamics n stucked with concepts related to enthalpy n internal energy..
my Q is why internal energy is function of V,T & enthalpy function of P,T
plz someone help me

Voltage comparator with variable voltage input. How?!

Posted: 08 Jan 2011 12:49 PM PST

Hullo,
I think that the subject I chose is not the most appropriate but I couldn't find a better one.
Anyway, I am designing my first "serious" circuit. I will use it to manage the power from a bicycle dynamo (permanent magnet generator?). I want it to switch from the dynamo to a backup battery when the output of the dynamo is not sufficient to drive a high power led.
First of all, I will use a full wave bridge to get a DC output.
Then, I was thinking of using a relay followed by a comparator with a fixed voltage reference.
To help you help me,
At 8km/h no load the output voltage is 15V.
At 8km/h with load the output voltage is 8V.
At 12km/h no load the output voltage is 17V.
At 12km/h with load the output voltage is 10V.

Let's say I set the threshold level of the comparator to 10V.
Under 10V, the battery is employed.

The problem:

The bicycle is still (0km/h)
[The comparator sees 0V from the dynamo and switches to the battery.
No problem here.]

The bicycle accelerates to e.g 8km/h and maintains this speed
[The dynamo has no load and its voltage is 15V, the comparator+relay switches to the dynamo. Now the dynamo is under load and its voltage drops to 8V, the comparator+relay now switches to the battery. The dynamo has no load and its voltage rises to 15V, the comparator+relay switches to the dynamo.
That is the problem I am facing. If my logic is correct, this oscillation will keep happening as long as my speed is below 12km/h.]

The bicycle accelerates to e.g 15km/h and maintains this speed
[The dynamo's output is above the threshold level, the comparator+relay switches to the dynamo. The dynamo's output WITH load is still above the threshold level.
No problem here.]

The bicycle decelerates to 8km/h and maintains this speed
[Like before, the same problem with the oscillation occurs.]

The bicycle decelerates to 0km/h and stays still
[The comparator sees 0V from the dynamo and switches to the battery.
No problem here.]

In conclusion, the problem is when the bicycle's speed is 0km/h<U<12km/h.
What can I do to overcome this?
I hope that my question is clear because english is not my native language.
If something is not clear or wrong please point it out.

Turbine Supervisory Instruments

Posted: 08 Jan 2011 12:38 PM PST

Turbine Supervisory Instruments

The following supervisory instruments are furnished with the unit and are to be observed during start-up, operation and shutdown. We will explain the following instruments in detail as follows.

1- Casing Expansion
As a unit is taken from its cold condition to its hot and loaded state, the thermal changes in the casings will cause it to expand.
The Casing expansion scale measures the movement of the force pedestal relative to a fixed point (the foundation). It indicates expansion and contraction of the casings during starting and stopping period, and for changes in load, steam temperatures.
Should it fail to indicate during these transient conditions, the situation should be investigated? The relative position of the fore pedestal should be essentially the same for similar conditions of load, steam conditions, vacuum, etc.

2- Rotor Position
Rotor Position instrument measures the relative axial position of the turbine rotor thrust collar with respect to the first bearing support. The thrust collar exerts a pressure against the thrust shoes, which are located on both sides of the thrust collar. Wear on the thrust shoes results in an axial movement of the rotor and is indicated on these instruments.
This instrument is equipped with an alarm relay which activates if the rotor moves beyond a predetermined distance. Continued movement beyond a second predetermined distance activates rotor position trip relay which trip the turbine via the emergency trip system.

3- Differential Expansion
When steam is admitted to a turbine, both the rotating parts and the casings will expand. Because of its smaller mass, the rotor will heat faster and therefore expand faster than the casings.
Axial clearances between the rotating and the stationary parts are provided to allow for differential expansion in the turbine, but contact between the rotating and stationary parts may occur if the allowable differential expansion limits are exceeded. The purpose of the differential expansion meter is to chart the relative motion of the rotating and stationary parts. It gives a continuous indication of the axial clearance while the turbine is in operation.
The instrument is equipped with alarm relay which activates if the value reaches the alarm point. As the rotating and stationary parts become equally heated after a transient condition, the deferential expansion will decrease.

4- Rotor Eccentricity
When a turbine has been shut down, the rotor will tend to bow due to uneven cooling if the upper half of the casing enclosing the rotor is at a higher temperature than the lower half. By rotating the rotor slowly on turning gear, the rotor will be subjected to more uniform temperature, thereby minimizing bowing.
This bowing of the rotor is recorded continuously as eccentricity from turning gear speed to approximately 600 rpm. The eccentricity instrument is equipped with an alarm signal which activates when the eccentricity reaches the alarm point.

5-Vibration
The vibration instrument is used to measure and record vibration of a turbine rotor at speeds above 600rpm. Below this speed, the rotor bowing is recorded as eccentricity.
The vibrations are measured on the rotor near the main bearings. Excessive vibrations serve as a warning for abnormal and possible hazardous conditions in the turbine. Each vibration instrument is equipped with alarm and trip relays which activates when excessive vibrations are measured at any one of the bearings.

Bridge engineering books

Posted: 08 Jan 2011 10:26 AM PST

Bridge Design Books

Posted: 08 Jan 2011 10:22 AM PST

Hi active brainzz...!!!

Posted: 08 Jan 2011 09:17 AM PST

Am Siva.v.Girish @ Anish.;-);-);-)
I used to feel very much better when others call me as shiva or chimp which is my nick name. I love thinking about logics and creating new logics too. very fond of making friends. And am doing my final year BE ECE in MEPCO SCHLENK ENGINEERING COLLEGE.

My most lovable hobby is to think about something related with science. and i think i have got a right place for my appetite too...

Technovision'11

Posted: 08 Jan 2011 06:22 AM PST

TECHNOVISION'11 is the technical paper presentation event of TROIKA, the annual technical fest of IEEE student branch of Delhi Technological University (formerly Delhi College of Engineering), Delhi organized in the month of February, 2011.
Over the years, Technovision has witnessed an exceptionally enthusiastic participation from students from across the country. Not just the students, but companies like Nokia, Schneider Electric and STMicroelectronics have been involved with it.
Papers are invited pertaining to the following streams of science and technology:
1. Electrical and Electronics Engineering
2. Computer Science and Information Technology
3. Bio-Technology
4. Renewable Energy and Sustainable Technology

A softcopy of the paper has to be sent at: technovision@dcetech.com and 3 hardcopies are to be sent at the postal address as mentioned in the Rulebook by 3rd Feb 2011. Rulebook can be downloaded from TROIKA'10 Delhi Technological University .

For further details contact:

Vipul Gupta vipul.gupta2012@gmail.com
Sakshi Arora sakshiarora1310@gmail.com
Twinkle Gupta tg2081990@gmail.com

SolidWorks - From Dream to Design

Posted: 08 Jan 2011 03:29 AM PST

I found this video by SolidWorks simply awesome.

Watch this:

SEA's Virtual Internship Program, February 7 – April 29, 2011

Posted: 08 Jan 2011 03:08 AM PST

SEA i.e. Scientists and Engineers for America has been offering a virtual internship program for more than last 2 years.

Our interns spend eight to ten hours each week researching specific science policy issues such as obesity, bioethics, climate change, biofuels and water security. Led by one of SEA's Fellows – a post-doctoral scholars with science outreach or leadership experience, teams of interns discuss weekly readings over a conference call and/or chat room format. Weekly reading assignments are often supplemented with writing assignments such as opinion pieces, letters to the editor, or policy briefs.

For the Spring 2011 Virtual Intern Application, see the information below.

To apply, please copy and paste this information into a Word document.

VIRTUAL SCIENCE POLICY INTERNSHIP PROGRAM
Spring 2011 Application
Final Application Due Date: January 10, 2010.

Internship Start and End Dates: February 7 – April 29, 2011.
Mission: As a nonprofit organization, SEA promotes evidence-based decision making at all levels of government. We pursue this mission by encouraging members of the scientific community to become engaged in US politics and the policy-making process.
Internship details:
SEA invites undergraduate and graduate students to take part in this Virtual Science Policy Internship Program. During this twelve-week course, interns dedicate eight to ten hours each week to studying specific areas of science policy, science communication and the various and often unknown ways that members of the US science communities positively influence public policy.
Interns collaborate in groups to analyze weekly readings, write policy briefs, and develop substantial and persuasive talking points. Intern research teams are led by Science Policy Fellows – postdoctoral scholars and science communicators. Science Policy Fellows help interns to develop confidence within a given research area, encouraging creative problem-solving through lively weekly conference calls, and offering advice to young scientists, engineers and health professionals who are still working to solidify their future goals.
Specific internship requirements (per week):
4 hours: Independent research and analysis.
2 hours: Research team conference calls, preparation and participation.
2 hours: Independent writing assignments.

Required Information
Name:
Email address:
Home phone/cell phone:
Mailing Address (Street & Apt #, City, State, ZIP):
Permanent Address:
Languages (Check all that apply): ___ Spanish
___ Chinese
___ Other: __________________
Education Information
Current School:
Check one of the following: ___ College
___ Trade School
___ Graduate School
Graduation Year:
Academic Concentration(s):
Extracurricular Activities:

For more information Visit : Scientists & Engineers for America

First Day At College : Share Your Story

Posted: 08 Jan 2011 02:57 AM PST

First day at the College (especially when you are an engineering student) is always a memorable one.

Some start their engineering life with pranks/mischief , some with new friends (that stick to you till the last day), some with being ragged (by seniors), some with punishments, some with excitement.

Share your memory of the first day at your college. :cean:

guide needed for fina year project-IT

Posted: 08 Jan 2011 02:18 AM PST

hi friends,i am doing a project in detecting the pose of object/human in a video.any regarding how to start or go about the project is highly appreciated.any links or books or any other source of information from u would be of great help......plz post the info however little u know.....

DC linear solenoid

Posted: 08 Jan 2011 01:01 AM PST

I am using a DC push-type solenoid as the mechanism for shooting in my robotics project. I have to use 12V DC supply and have to shoot TT balls for distances upto 3-7 feet. The solenoid specifications suggest that it requires 60 amp current. How do i generate this??
Thanks in advance

Facebook Connection Enabled : Help Us Test It

Posted: 08 Jan 2011 12:53 AM PST

CEans,

We've integrated Facebook Login on CrazyEngineers. We'll also start supporting registration with Facebook ID.

If you have a facebook account, simply hit the F-Connect button above and connect your facebook account to your CrazyEngineers account :D

Let us know if you face any problems, issues in this thread. Also tell us if you do it successfully :D

iPad 2 Coming In Feb First Week- Kevin Rose

Posted: 07 Jan 2011 10:58 PM PST

iPad2 will be launched in the first week of February 2011. It will have iPhone's Retina Display and also front and back end cameras.

If you are looking to buy an iPad, why not hold on for a few days for iPad2?

Micromax EG333 Tata Photon+ Phone Review | Price In India

Posted: 07 Jan 2011 10:36 PM PST

EG333 By Micromax boasts High Speed Internet Access Provided By Tata Photon+ service. Micromax is known for Dual SIM phones and this phone supports Photon (CDMA) + (GSM) networks [ CDMA 800MHz, GSM900MHz / 1800MHz ].

A 2MP camera is bit disappointing, but do not expect great images with it. The phone has 7.62cm Full Touch Screen and with with a big screen, the phone only weighs just 130gms. The phone supports Internet tethering and you can use this phone as your computer modem. Of course you will have to install the dialer software bundled with the package.

Attachment 32

The USP of this phone is high speed internet access provided by Tata Photon+. With a 3.1 mbps connection the phone allows you to watch over 70 TV channels.

The phone has 1Gb Nand Flash + 512Mb SDRAM which is at part with the competition. The phone supports upto 4 GB of external memory via MicroSD card, but I'd have loved to see it upto 16 GB at least. Apart from these features, the phone has 2000+ entry phonebook, bluetooth, Java, GPRS. The battery is 1500 mAh+ which would last up to 7 days on regular usage (no heavy gaming, bluetooth, video usage).

In the Android days, I wonder how many will really want to buy this phone. The official price of the phone is yet to be released. So if you get any updates about this phone, please share them in this thread.

Attached Images

micromax-eg333.jpg (37.7 KB)

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