We have written this Appium tutorial to give a complete picture of Appium mobile automation. We will discuss all the major topics here.
Introduction
It is an open-source tool. It supports Android, iOS, windows OS. We can execute same code in different os versions like Android, iOS.It reduces redundant code and helps to increase code reusability. It has implemented the Selenium webDriver, which connects through Apple’s XCUITest(iOS 9.3 and above) or UIAutomation(iOS 9.3 and lower) or UiAutomator/UiAutomator2 (Android) or WinAppDriver(Windows) dependent on the type of devices.
We will cover the below topics in this Appiumtutorial:
Advantages of Appium
Disadvantages of Appium
Types of Mobile applications
There are three types of applications supported :
Native Application
Native applications are written using Windows, Android, iOS SDKs.
Hybrid Application
Hybrid applications are a mix of web and native applications. Here native applications have control, and it interacts with mobile web applications.
Mobile Application
Mobile web applications are web-based applications. These are accessible using chrome(Android), Safari(iOS) browser. We can develop this type of application by HTML, CSS, JavaScript, AngularJS.
Appium Architecture :
How It works on the iOS platform
How It works on the Android platform
Prerequisite for setup
Appium tutorial for installing Appium Desktop on Windows
Please go to http://appium.io/, and you will see the below screen. Please click on the below-highlighted button.
Please click on the download button
Once you have clicked the above button, you will see the below page. Please click on the highlighted .exe file or .zip file to get it downloaded in your system.
Please Download the .zip or exe file
Here We have taken the .zip file to install it. Please unzip the file. After that, you will see the image below. Please click on Appium.exe.
Unzip the file
Now you can see the image below, and you are ready to start your server.
Please start the server
Now you can see the image below, and your server is ready.
Server has started
Appium tutorial for installing Appium Desktop on Mac
Please go to http://appium.io/, and you will see the below screen. Please click on the highlighted button shown below.
Please click on download button
Once you have clicked the above button, you will see the below page. Please click on the highlighted dmg file to get it downloaded in your system.
Please download the dmg file
Please click on the dmg file, which got downloaded recently, and you will see the below screen. Please the instruction mentioned in the below image.
Please drag to Application folder
It will start copying in the Application folder.
Copying started
Suppose you have already installed another version in your system. You will get below pop up. It is your choice to keep both or replace the older one.
You cab keep both or replace one
Once it is installed in your system, you can go to the launchpad and search with Appium, and you will get below icon and click on the icon. Alternatively, you can go to the Application folder and click on the icon.
Please search for the icon
Many times after launching it, you can get below error messages. No need to worry; we can solve this issue.
Security error
To solve the above issue, you have to go to system preference from the apple icon shown on the top left corner and then click on Security and privacy. You will see the screen below. Please click on “Open Anyway.”
Please go to privacy settings, and click on Open Anyway
Now click on the icon once again and this time, choose to open it. Please follow the below image.
Please Click on Open
Now you can see the image below, and you are ready to start your server.
Please start the server
Please click on the start server to start the server. Your screen will look like below.
Server Started
conclusion
Till now We have covered the basics of Appium mobile testing in this Appium Tutorial. In the next topic, We will write about top 20 most used methods to automate native application. For more details on this topic, please refer to this link.
Nonlinear optics is a field of study that explores the interaction between light and matter, leading to phenomena such as frequency conversion, wave mixing, and self-phase modulation. This field is crucial for applications in optical telecommunications, imaging, and spectroscopy. In this comprehensive guide, we will delve into the detailed analysis of nonlinear optics, covering various aspects of this fascinating subject.
Measurement and Interpretation of Nonlinear Optical Effects
One key aspect of nonlinear optics is the measurement and interpretation of nonlinear optical effects. The review by Vincenti et al. discusses recent developments in experimental methodologies for the quantitative measurement and interpretation of optical second harmonic generation (SHG) from molecular interfaces. SHG is a second-order nonlinear optical process that generates light at twice the frequency of the incident light.
The review focuses on the use of SHG for quantitative analysis of the nonlinear optical properties of materials, including the determination of molecular orientation and conformation at interfaces. The authors present a detailed analysis of the theoretical framework for SHG, which involves the calculation of the second-order nonlinear susceptibility tensor. They also discuss the experimental techniques used to measure SHG, such as angle-resolved SHG and polarization-dependent SHG.
Furthermore, the review highlights the importance of properly accounting for the local field effects and the influence of the substrate on the measured SHG signal. The authors provide guidelines for the interpretation of SHG data, including the extraction of molecular orientation and conformation information from the experimental results.
Analysis of the Underlying Physics of Nonlinear Effects
Another important aspect of nonlinear optics is the analysis of the underlying physics of nonlinear effects. The method proposed by El-Desouky et al. provides a more accurate understanding of the physics of entangled nonlinear optics effects in spectral broadening through solid media of femtosecond pulses.
The method uses a neural network to quantify and analyze the nonlinear effects, leading to a faster and more convenient approach compared to traditional methods. The authors present a detailed mathematical formulation of the problem, which involves the solution of the nonlinear Schrödinger equation (NLSE) governing the propagation of ultrashort pulses in nonlinear media.
The neural network is trained to learn the mapping between the input pulse parameters (such as pulse duration, peak power, and wavelength) and the output spectral characteristics (such as bandwidth and spectral shape). The authors demonstrate the accuracy and efficiency of their method through numerical simulations and experimental validation.
Nonlinear Optical Response in Low-Index Media
The paper by Fryett et al. shows that standard approximations in nonlinear optics are violated for situations involving a small value of the linear refractive index. This means that the conventional equation for the intensity-dependent refractive index becomes inapplicable in epsilon-near-zero (ENZ) and low-index media, even in the presence of only third-order effects.
The authors provide a detailed analysis of the nonlinear optical response in these media, which cannot be interpreted as a perturbation. They derive a new expression for the nonlinear refractive index that takes into account the strong field enhancement and the breakdown of the perturbative description.
The paper focuses on the particular case of indium tin oxide (ITO), a material with a low linear refractive index near the ENZ wavelength. The authors demonstrate that the nonlinear response of ITO cannot be described by the standard Kerr effect and requires a non-perturbative treatment.
Practical Considerations and DIY Aspects
When it comes to the practical application of nonlinear optics, practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information. This is because nonlinear optics involves complex interactions between light and matter that require a deep understanding of the underlying physics and experimental techniques.
For instance, the choice of nonlinear optical materials, the design of the experimental setup, and the interpretation of the results all require a thorough understanding of the subject. Researchers must be familiar with the various nonlinear optical processes, their mathematical descriptions, and the associated physical phenomena.
Additionally, the implementation of nonlinear optical devices, such as frequency converters, optical parametric oscillators, and self-phase modulators, requires a detailed knowledge of the specific device characteristics, optimization techniques, and practical limitations.
Conclusion
In summary, this comprehensive guide has provided a detailed analysis of various aspects of nonlinear optics, including the measurement and interpretation of nonlinear optical effects, the analysis of the underlying physics, and the practical considerations for the application of this knowledge.
By understanding the theoretical foundations, experimental methodologies, and practical challenges in nonlinear optics, researchers and practitioners can effectively navigate this field and contribute to the advancement of optical technologies.
Taylor K. Fryett, Alan Zhan, and Arka Majumdar, “Beyond the perturbative description of the nonlinear optical response in epsilon-near-zero media,” Optics Express, vol. 42, no. 16, pp. 3225-3233, 2017, https://opg.optica.org/ol/abstract.cfm?uri=ol-42-16-3225
Integer quis nisl at orci feugiat lobortis quis a odio. Etiam efficitur metus ultricies nisl lacinia malesuada. Mauris ante eros, convallis vitae eros ut, congue placerat ante. Etiam metus massa, volutpat sit amet sapien ut, condimentum ultricies dui. In mauris metus, semper eu consequat eget, porttitor sed dui. Nam eu hendrerit nibh. Mauris vulputate lectus … Read more
UiPath is the agent for the main computerized method for automation technology. It helps in building the product is ready to deliver , which will assist in a union like computerize job.
2. Discuss a few reliable RPA tools?
There are primarily three admired RPA tools which are mentioned below:
Blue Prism:
Blue Prism tool recommended business performance to be agile and low cost by automating rule-based, monotonous back-office process.
Automation Anywhere:
Automation Anywhere provides robust and user-friendly RPA tools to automate jobs of any difficulty.
UiPath:
UiPath is a Windows desktop tool applicable for automation for many types of web and desktop-based applications.
3. Tell me the activities which you have used in Pdf Automation?
Primarily used activities are Read pdf text, Read pdf with OCR & Get text.
4.Tell me the process of filtering the mail using Uipath?
There are two process for filtering the E-mails.
It can be strained using “if condition” in “for each” loop.
Users can provide filter conditions in the get Outlook filter choice.
5. Provide the steps to install Google Chrome Extension for UiPath Studio?
Below are the steps to install Google Chrome Extension for UiPath Studio:
Go to Setup ribbon tab, from the “Setup Extensions” menu, Choose Chrome. The Chrome Web Store is initiated in Google Chrome.
Setup Extension1
Click the “Add to Chrome” A verification dialogue box will have appeared.
Select the “Add extension” The extension will be installed.
Setup Extension2
Remark: Usually by default extension is kept off.
6. What do you understand by PDF Automation?
Pdf Automation is a special type of automation where the user can retrieve all the information from a pdf file.
7. What are the different type of navigation of Orchestrator?
There are more than eight types of navigation in Orchestrator alike Robot, Schedule, asset, Queue, Machine and process.
8. Tell me the method to schedule a process through Orchestrator?
There is a scheduler choice in Orchestrator options using that user can schedule the process.
9. What is Reframe work?
Reframe work is solely based on state machine and Entirely flow is State Machine. There are three states & one final states.
There are subprocess, sub modules& mini processes.
User can divide the process into different smaller projects.
10. What is the process for deploying UiPath tool?
1. Finish the installation of UiPath Studio on the desired system on which user want to automate processes.
2. Publish the scheme, except if user needs to use the existing procedure.
3. Build an Environment.
4. Create a release of the rule on the same environment.
5. Start the job
11. Tell me the process to activate UiPath Studio license?
To activate the UiPath Studio license, the user must keep the system Online. Steps are mentioned below.
Click the “Activate License”, the license window will appear.
Please provide an email id and continue to next step.
Provide the license key.
Select “Automatic activation.”
Select the “Activate”, UiPath license is now activated in the user’s system, and the user can begin building automation workflows.
License Activation
12. What is the invoking process of a UiPath workflow?
Workflows are short pieces of standard automation that are recyclable and applicable in many synopses. They are used to automate similar methods. Users can also merge two workflows to make combined automation.
13. How would you deploy UiPath?
Install UiPath Studio on the computer on which the user wants to automate processes.
Publish the process, omitting if user simply wants to make use of their existing process.
Develop an Environment.
On that Environment, make a release process.
Start job.
14. Discuss all the different status of a Robot.
Available: The Robot is not running a process and is available to be used.
Busy: The Robot is executing a process.
Disconnected: Communication has been lost or disconnected for more than 2 minutes between the Robot and Orchestrator.
4. Unresponsive: The UiPath Robot service is not working.
15. Tell me the process to allocate the load between different bots?
If you are engaging with reframe job queue functionality & if you desire to share the pressure among different workflow, then you can build two frameworks, first one is dispatcher which object is to upload data on Queue and the second one is a performer for receive the data from Queue.
16. Give a brief of UiPath tool components?
Components of UiPath tool mentioned below
UiPath studio: It is a tool; the user can create and develop their own Project using the diagrams and visually.
UiPath Robot: Usually named as a bot, using the bot user can run Project in various computers.
UiPath Orchestrator: Its an application, using this application user can deploy their Projects and use it in any place.
It’s used for Project optimization; the user can deploy, schedule, monitor the execution and extract report and update respective Team.
17. What do you mean by an argument in UiPath tool?
An argument is required to pass the data into one project to another.
18. Tell me project creation steps and the execution process.
Steps for creating the Project creation steps mentioned below:
Launch the UiPath Studio and start.
Create a new Project using below steps:
New
Simple process.
Agent Process Implementation.
Follow the ordered sequence for Transaction.
Use a new tab, Provide the name and required path and also mentioned details after creating the project.
Depends on the project design window will open.
Drag and drop the schemas into the design window
Now you can execute the project clicking the RUN button else you can press F5 button from your keyboard.
19. Clarify these two terms “Delay Before” and “Delay after”
Delay Before:
Before the operation executes it wait for the designated time and then it will perform.
Delay After:
Once the operation is executed, it waits for the designated time and performs the next process.
The delay Time should be only on milliseconds like 5000.
20. Discuss the different types of Workflows in the UiPath tool?
Sequences: The sequence is really the small type of projects which are acceptable primarily for linear methods & will permit the user to swap from one activity to another without any trouble. It works as a single activity block. Users can reuse them several times.
Flowchart: It helps in enormous jobs as well as in short projects, and the user can also use them in various projects. Flowcharts assists in several dispencing dividing of logical operators assist in developing composite business and for attaching the ventures in multiple ways.
State Machine: while a machine is using a specific number of states for automation throughout the execution process, it is also familiar as the state machine. It will only shift from one state to another if any activity is triggered.
21. Why do we need “branching” in the UiPath tool?
When we want to connect the activities, we need the branching in the Flowchart.
22. Cloud you, please explain the “Partial Selectors”?
The selector information described in attach window or in the connected browser is the partial selectors.
23. Tell me some Wildcards in the UiPath tool?
There are two wildcards.
Asterisk (*): Replaces zero or more characters.
Question mark (?): Replaces a single character.
24. What are the dissimilarities between the Attended and Unattended bot in UiPath tool?
1. Attended Robot: Attended Robot is triggered by user events, and serves beside a human, on the same workstation. AttendedRobots are practiced with Orchestrator for a centralized method deployment and logging medium.
2. UnattendedRobot: UnattendedRobot Runs abandoned in virtual environments and can automate an uncountable number of processes. Apart from that, unattended Robot is capable of job scheduling remote execution, monitoring and providing support for work queues.
25. Describe Automatic Recording in UiPath tool?
Automatic recording is very helpful and efficient as it can supply the users with a framework for business processes and can be efficiently customized and parameterized.
26. What is the use of the output panel in the UiPath Tool?
The output panel helps the programmer to view the execution results.
27. What is the different process to create variables in UiPath?
User can create a variable in two ways:
From a variable window, using ctrl+k in the property window.
Click on the Variable Pane in the toolbar.
28. Tell me the use of an outline panel in UiPath?
The Outline panel displays variables, all nodes, and the project hierarchy.
29. What are the sections available in the UiPath tool?
There are six sections are available in UiPath
1) Projects Panel.
2) Activity Panel.
3) Workflow Designer/ Main Panel.
4) Property Panel.
5) Output Panel
6) Outline Panel
UiPath Panel
30. What is the responsibility of an Orchestration job?
The primary authority is to organize the implementation of different jobs.
31. what are the processed to filter mail using the UiPath tool?
Two methods are used to filter the emails:
Emails can be filtered using if condition in for each loop.
Users can also filter email by implementing a filter condition in the “Get outlook” filter selection.
32. What do you understand by “credential manager” in the UiPath tool?
The credential manager assists developers in automating the methods. It is used for designing, making, as well as deleting the
credential using committed tasks.
33. Discuss “sequence activities” in the UiPath tool?
The sequence is a kind of project which are acceptable mainly for linear methods and will permit users to traverse from one activity to another without any hassle. It basically works as a single activity block. Users can reuse them many times.
34. How to automate excel macro using the UiPath tool?
Automating the excel macro using UiPath is achieved by executing macro activity installed from the manage package window.
35. What are the properties in UiPath?
There are different activities applied to automate applications or web-applications, and the user can discover them in the Activities Panel, inside the UI Automation section.
All of these activities have various properties in common:
Delay after: Adds a pause after the action, in milliseconds.
Delay before: Adds a pause before the action in milliseconds.
TimeoutMS: Defines the measure of time (in milliseconds) to wait for a particular element to be found before any error is thrown. The default value is 30000 milliseconds.
WaitForReady: Before executing the actions, wait for the target to become ready.
36. Describe the process of publishing a project in the UiPath tool?
When a developer or Tester wishes to publish an automation project, that implies document the workflow and all the other packages to be transferred to Robots. After configuring the Robot with the required infrastructure, the project can be executed.
Publishing projects locally needs the user to provide a path on the local machine, different from where the scripting packages are published. There, the user can later manually send the packages to the Robots to be executed.
37. Tell me the process of storing credentials in the window and utilize by UiPath tool?
Users will take secure credential activity and fetch that user-id and Password in two variables and pass into a web application or automate whatever process.
38. Discuss the “Automatic Recording” feature in the UiPath tool?
Users should use row below command: (“ColumnName”).ToString.Equals(String.Empty). This command returns a Boolean value, which authenticates empty columns in Excel.
39. Difference between sequence and flow chart in UiPath?
Sequence:
The sequence is a kind of project which are acceptable mainly for linear methods and will permit users to traverse from one activity to another without any hassle. It basically works as a single activity block. Users can reuse them many times.
Flowchart:
The flowchart is normally used for general configuration purpose in UiPath. User can use these flow charts for different types of projects for all complexity and length. Flowcharts assists the functions in creating and isolating the logical operations, in creating the complex business models, and merge various sequences.
40. Brief us the dis-similarities between RPA and the chatbot?
There are many dis-similarities between RPA and the chatbot few are mentioned below .
RPA (Robotic process automation): RPA is a broader supposition and chatbot is a very small or sub-group of RPA topic. RPA is used to automate the cumbersome processes but chatbot cannot automate the same complex process.
Chatbot: A bot is a pre-organized tool which works like a human. These chatbots assist the guests to operate some planned actions. The good thing about chatbots is that bots educate themselves from previous experiences and act as per the situation.
41. Discuss the assets configure process in Orchestrator?
Step1: Login to Orchestrator.
Step2: Select the assets option from left menu panel.
Step3: Add asset.
Step4: Provide asset name and Select type of asset.
Step5: Please keep in mind, you must have to disable the Global Value.
Step6: Add Robot name (Select the robot name if it is already existing in your dropdown list). Step7: Provide the password and click on create.
UiPath interview questions and answers: asset creation
42. Describe thick client and thin client in UiPath?
A Thin client is an application where the user cannot get all assets that he/she required while using the RPA tool. Basically, a thin client is an automation involvement done on the browser. Example: Citrix.
Thick client: Thick client is an application where the user will obtain all the attributes that are needed for the RPA tool. Basically, Thick client involved in Desktop application automation. Example: SAP GUI.
43. What are the changes required while publishing a new package for Bot?
Step1: After publishing a new package, user need to update with latest package in Orchestrator package section.
Step2: Next user need to download the package in “UiPath Robot agent”
Step3: Finally, user need to download the latest package in version management.
Integer quis nisl at orci feugiat lobortis quis a odio. Etiam efficitur metus ultricies nisl lacinia malesuada. Mauris ante eros, convallis vitae eros ut, congue placerat ante. Etiam metus massa, volutpat sit amet sapien ut, condimentum ultricies dui. In mauris metus, semper eu consequat eget, porttitor sed dui. Nam eu hendrerit nibh. Mauris vulputate lectus … Read more
Integer quis nisl at orci feugiat lobortis quis a odio. Etiam efficitur metus ultricies nisl lacinia malesuada. Mauris ante eros, convallis vitae eros ut, congue placerat ante. Etiam metus massa, volutpat sit amet sapien ut, condimentum ultricies dui. In mauris metus, semper eu consequat eget, porttitor sed dui. Nam eu hendrerit nibh. Mauris vulputate lectus … Read more
In this article we will study about the Schmitt trigger Comparator and Oscillator circuitry with different related parameters in detail. As we have seen till now that an op-amp is used in various fields of applications and being such a versatile device its importance as a part of analog circuits is immense. One of the most convenient applications of the op-amp is as a multivibrator circuit. We will be studying in detail about types and working of multivibrator circuit constructed using op-amps (op-amp multivibrators) and other passive devices such as capacitors, diodes, resistors etc.
Contents
Introduction of Multivibrators
Positive feedback usage in multivibrator
What is Schmitt trigger ?
Schmitt trigger comparator closed-loop circuit or bistable multivibrator
Voltage transfer characteristics of Bistable multivibrator
Astable multivibrator or Schmitt trigger oscillator
Oscillator’s duty cycle
Introduction of Multivibrator and Schmitt trigger Circuitry
Multivibrator circuits are sequential logic circuits and are of many types depending on how they are created. Some multivibrators can be made using transistors and logic gates, whereas there are even dedicated chips available as multivibrators such as NE555 timer. The op-amp multivibrator circuit has a few advantages over other multivibrator circuits as they require much fewer components for their working, less biasing, and produces better symmetrical rectangular wave signals using comparatively fewer components.
Types of Multivibrators
There are mainly three types of multivibrator circuits present:
Astable multivibrator,
Monostable multivibrator
Bistable multivibrator.
The monostable multivibrator has single stable state, whereas the number of stable-states a bistable multivibrator has- is 2.
As we have learnt in the previous section about op-amp as a comparator, in the open-loop configuration the comparator can switch in an out of control manner between the positive saturation supply rail voltage and negative saturation supply rail voltage when an input voltage near to that of the reference voltage is applied. Hence, to have control on this uncontrollable switching between the two states, the op-amp is used in a feedback configuration (closed-loop circuit) which is particularly known as closed-loop Schmitt trigger circuit or bistable multivibrator.
Positive feedback usage in multivibrator and hysteresis effect
Till now, we have learnt about the negative feedback configuration in op-amps in the previous sections. There is also another type of feedback configuration known as positive feedback, which is also used for specific applications. In positive feedback configuration, the output voltage is fed back (connected) to the non-inverting (positive) input terminal unlike the negative feedback, where the output voltage was connected to the inverting (negative) input terminal.
An op-amp operated in a positive feedback configuration tends to stay in that particular output state in which it is present, i.e. either the saturated positive or saturated negative state. Technically, this latching behaviour in one of the two states is known as hysteresis.
If the input applied signal in the comparator consists of some additional harmonics or spikes (noise), then the output of the comparator might switch to the two saturated states unexpectedly and uncontrollably. In this case, we won’t get a regular symmetrical square wave output of the applied input sinusoidal waveform.
But if we add some positive feedback to the comparator input signal, i.e. use the comparator in a positive feedback configuration; we will be introducing a latching behaviour in the states, what we technically call as hysteresis into the output. Until and unless there is a major change in the magnitude of the input AC (sinusoidal) voltage signal, the hysteresis effect will continue to make the output of the circuit remain in its current state.
What is Schmitt trigger ?
The Schmitt trigger or bi-stable multi-vibrator operates in positive feedback configuration with a loop-gain greater than unity to perform as a bi-stable mode. Voltage V+ can be.
Schmitt trigger comparator or bistable multivibrator
The Voltage transfer characteristics of Schmitt trigger Comparator
The above figure represents the output voltage versus the input voltage curve (which is also known as the voltage transfer characteristics), particularly showing the hysteresis effect. The transfer characteristic curve has two specific regions, the curve as the input voltage increases and the part of the curve in which the input voltage decreases. The voltage V+ does not have a constant value, but instead, it is a function of the output voltage V0.
Voltage transfer characteristics
In the voltage transfer characteristics, Vo = VH, or in high state. Then,
Higher Cross-over voltage VTH
If signal is less than that of V+, the output stays at its high state. The cross-over voltage VTH occurs when Vi = V+ and expressed as follows:
When Vi > VTH, the voltage at the inverting terminal is more than at the non-inverting terminal. Voltage V+ then turn out to be
Lower Cross-over voltage VTL
Since VL < VH the input voltage Vi is still more than V+, and the output rests in its low state as Vi carry on to increase; If Vi decreases, as long as the input voltage Vi is larger than V+, the output remains at saturation state. The cross-over voltage here and now occurs when Vi = V+ and this VTL expressed as
As Vi continues to decrease, it remains less than V+; therefore, V0 remains in its high state. We can observe this transfer characteristic in the above figure. A hysteresis effect is shown in the net transfer characteristic diagram.
What is Schmitt trigger oscillator ?
Astable multivibrator or Schmitt trigger oscillator
Astable multivibrator accomplished by fixing an RC network to the Schmitt trigger circuit in –ve feedback. As we will advance through the section, we will see that the circuit has no stable states and therefore, it also known as the astable multivibrator circuit.
Astable Multivibrator circuit or Schmitt trigger Oscillator
As noticed in the figure, an RC network is set in the negative feedback path, and the inverting input terminal is connected to the ground through the capacitor while the non-inverting terminal is connected to the junction between the resistors R1 and R2 as shown in the figure.
At first, R1 and R2 is to be equal to R, and assume the output switches symmetrically about zero volts, with the high saturated output represented by VH = VP and low saturated output indicated by VL = -VP. If V0 is low, or V0 = -VP, then V+ = -(1/2)VP.
When Vx drops just slightly below V+, the output switches to high so that V0 = +VP and V+ = +(1/2)VP. The equation for the voltage across the capacitor in an RC network can be expressed as:
Where τx is the time constant which can be defined asτx= RxCx. The voltage Vx increases towards a final voltage VP in an exponential manner with respect to time. However, when Vx turn out to be slightly greater than V+ = +(1/2)VP, the output shifts to its low state of V0 = -VP and Vx = -(1/2)VP. The RxCx network gets triggered by a negative sharp transition of the voltages, and hence, the capacitor Cx start discharging, and the voltage Vx decreasing towards value of –VP. We can therefore express Vx as
Where t1 refers to the time instant when the output of the circuit switches to its low state. The capacitor discharge exponentially V+ = -(1/2)VP, the output again shifts to high. The process repeats itself continuously over time, which means a square-wave output signal is produced by the oscillations of this positive feedback circuit. The figure below shows the output voltage V0 and the capacitor voltage Vx with respect to time.
The Schmitt Trigger Oscillator: Plot of Output voltage and Capacitor Voltage with respect to time
Time t1 can be found by substituting t=t1 and Vx = VP/2 in the general equation for the voltage across the capacitor.
From the above equation when we solve for t1, we get
For time t2 (as observed in the above figure), we approach in a similar way, and, from a similar analysis using the above equation, it is evident that the difference between t2 and t1 is also 1.1RxCx. From this, we can infer that the time period of oscillation T can be defined as T = 2.2 RxCx
And the frequency thus can be expressed as
Duty cycle of Oscillator
The percentage of time the output voltage (V0) of the multi-vibrator is in its high state is particularly termed as the duty cycle of the oscillator.
The oscillator’s duty cycle is
As observed in the figure, depicting output voltage and capacitor voltage versus time, the duty cycle is 50%.
The mesosphere is the third layer of the Earth’s atmosphere, located above the stratosphere and below the thermosphere. It extends from approximately 50 to 90 kilometers above the Earth’s surface, playing a crucial role in various atmospheric phenomena and processes.
Characteristics of the Mesosphere
Temperature Profile
In the mesosphere, temperature decreases with increasing altitude, reaching a minimum of about -90°C at the “mesopause,” which is the boundary between the mesosphere and the thermosphere.
This temperature decrease is due to the absorption of solar radiation by ozone (O₃) in the stratosphere, which heats the lower atmosphere, and the lack of significant heat sources in the mesosphere.
Composition and Structure
The mesosphere is primarily composed of nitrogen (N₂) and oxygen (O₂), with trace amounts of other gases such as carbon dioxide (CO₂), water vapor (H₂O), and methane (CH₄).
The density of the atmosphere decreases exponentially with altitude, with the mesosphere being much less dense than the lower atmosphere.
The mesopause, the boundary between the mesosphere and the thermosphere, is characterized by a sharp temperature inversion, where the temperature begins to increase again.
Atmospheric Phenomena
Meteor Burning: The mesosphere is the layer where most meteors burn up upon entering the Earth’s atmosphere. This is due to the high-speed collisions between meteoroids and the molecules in the mesosphere, which cause the meteoroids to heat up and disintegrate.
Noctilucent Clouds: These thin, wispy clouds form in the mesosphere during the summer months and are visible at night. They are composed of ice crystals and are the highest clouds in the Earth’s atmosphere.
Polar Mesospheric Summer Echoes (PMSEs): These phenomena occur when radio waves bounce off the charged particles in the mesosphere, which are created by the interaction between solar radiation and the atmosphere.
Atmospheric Gravity Waves: These waves are generated in the troposphere and propagate upward into the mesosphere, where they can interact with the background wind and temperature structure, leading to the formation of various atmospheric phenomena.
Importance of the Mesosphere
Climate and Weather Studies: The mesosphere is an important region for studying the Earth’s climate and weather patterns, as it is the layer where many atmospheric phenomena occur.
Magnetic Field and Charged Particles: The mesosphere is where the Earth’s magnetic field lines converge, trapping charged particles and creating the Van Allen “radiation” belts. This makes the mesosphere an important region for studying the Earth’s magnetic field and the behavior of charged particles in the atmosphere.
Atmospheric Dynamics: The mesosphere is a crucial layer for understanding the dynamics of the Earth’s atmosphere, as it is the region where various atmospheric processes, such as the propagation of gravity waves and the formation of noctilucent clouds, take place.
Studying the Mesosphere
Challenges
The mesosphere is a challenging layer to study due to its high altitude and the harsh conditions that exist there, such as extremely low temperatures and low atmospheric density.
Direct in-situ measurements in the mesosphere are difficult to obtain, as the region is beyond the reach of most conventional aircraft and balloons.
Measurement Techniques
Rockets: Sounding rockets are used to launch instruments into the mesosphere, allowing for direct measurements of various parameters, such as temperature, pressure, and chemical composition.
Balloons: High-altitude balloons can reach the lower regions of the mesosphere, providing valuable data on atmospheric conditions.
Lidars (Light Detection and Ranging): These remote sensing instruments use laser beams to measure various atmospheric properties, such as temperature, wind, and the presence of aerosols and clouds, in the mesosphere.
Satellite Observations: Satellites equipped with specialized instruments can provide global-scale measurements of the mesosphere, including temperature, composition, and the occurrence of atmospheric phenomena.
Ground-based Observations: Ground-based instruments, such as radars and spectrometers, can be used to study the mesosphere by detecting and analyzing various atmospheric signals, such as PMSEs and noctilucent clouds.
Numerical Modeling
Sophisticated computer models, such as general circulation models (GCMs) and chemistry-climate models, are used to simulate the complex processes and interactions within the mesosphere, allowing for a better understanding of its role in the Earth’s atmospheric system.
These models incorporate various physical, chemical, and dynamical processes to provide insights into the mesosphere’s behavior and its interactions with other atmospheric layers.
Advances in Mesospheric Research
Improved Measurement Techniques
Advancements in rocket, balloon, and lidar technologies have enabled more accurate and detailed measurements of the mesosphere, leading to a better understanding of its physical and chemical properties.
Satellite-based observations have provided a global perspective on mesospheric phenomena, allowing for the study of large-scale patterns and trends.
Numerical Modeling Improvements
Continuous advancements in computational power and the incorporation of more detailed physical and chemical processes have led to the development of increasingly sophisticated numerical models of the mesosphere.
These models have improved our ability to simulate and predict the behavior of the mesosphere, including its response to various natural and anthropogenic forcings.
Interdisciplinary Collaboration
The study of the mesosphere requires the integration of knowledge from various scientific disciplines, such as atmospheric physics, chemistry, and meteorology.
Collaborative efforts among researchers from different fields have led to a more comprehensive understanding of the mesosphere and its role in the Earth’s atmospheric system.
Conclusion
The mesosphere, the third layer of the Earth’s atmosphere, is a crucial region for understanding the Earth’s climate, weather patterns, magnetic field, and the behavior of charged particles in the atmosphere. Despite the challenges associated with studying this high-altitude layer, scientists have developed various tools and techniques to measure and analyze its properties, leading to significant advancements in our understanding of the mesosphere and its role in the Earth’s atmospheric system.
The stratosphere and troposphere are two distinct layers of the Earth’s atmosphere, each with its own unique characteristics and importance in the overall climate system. The stratosphere extends approximately 40 km above the tropopause and contains about 20% of the atmosphere’s mass, while the troposphere is the lowest layer of the atmosphere, extending from the surface up to the tropopause.
Understanding the Stratosphere
The stratosphere is a crucial component of the Earth’s climate system, playing an active role in various atmospheric processes. One of the notable features of the stratosphere is the presence of the ozone layer, which absorbs harmful ultraviolet radiation from the Sun, protecting life on Earth.
Temperature Inversions in the Stratosphere
The stratosphere is characterized by a temperature inversion, where temperature increases with altitude. This is in contrast to the troposphere, where temperature decreases with altitude. The temperature inversion in the stratosphere is caused by the absorption of solar radiation by ozone, which heats the upper layers of the stratosphere.
The temperature inversion in the stratosphere has several important implications:
Atmospheric Stability: The temperature inversion creates a stable layer of air, which inhibits vertical mixing and the formation of convective clouds. This stability can have a significant impact on weather patterns and the distribution of atmospheric constituents.
Ozone Layer Dynamics: The temperature inversion plays a crucial role in the dynamics of the ozone layer. The stable conditions in the stratosphere allow for the formation and maintenance of the ozone layer, which is essential for protecting life on Earth from harmful UV radiation.
Atmospheric Circulation: The temperature inversion in the stratosphere can influence the overall atmospheric circulation patterns, such as the formation of the polar vortex and the propagation of planetary waves.
Stratospheric Water Vapor
The stratosphere typically contains much less water vapor than the troposphere. However, the amount of water vapor in the stratosphere can have significant impacts on the Earth’s climate. An increase in stratospheric water vapor can enhance the greenhouse effect and contribute to global warming.
Using data from the SAGE III instrument on the International Space Station, scientists have been able to study the year-to-year variability of water vapor (H2O) during the boreal summer monsoon season. By analyzing multiple years of data, they can understand how much water vapor is transported into the stratosphere through the summer monsoon circulation.
Relative Humidity in the Stratosphere and Troposphere
Relative humidity (RH) is an important factor in studying the stratosphere and troposphere. RH tells us how much water vapor is in the air, relative to how much water vapor the air could hold at a given temperature. As air temperatures rise, warmer air can hold more water vapor, increasing the saturation point. Conversely, cold air can hold less water vapor.
The RH-temperature relationships captured by the SAGE III instrument agree with the near-tropopause data derived from high-resolution Upper Troposphere/Lower Stratosphere (UTLS) aircraft measurements. This enhances the scientific community’s confidence in the quality and reliability of the SAGE III data set.
Understanding the Troposphere
The troposphere is the lowest layer of the Earth’s atmosphere, extending from the surface up to the tropopause. It is the layer where we live and where most weather phenomena occur.
Temperature Lapse Rate in the Troposphere
The troposphere is characterized by a decrease in temperature with altitude, with an average lapse rate of about 6.5°C per kilometer. This temperature decrease is caused by the adiabatic cooling of air as it rises and expands.
The temperature lapse rate in the troposphere is an important factor in the formation and behavior of weather systems. It influences the stability of the atmosphere, the development of convective clouds, and the distribution of atmospheric constituents.
Atmospheric Composition in the Troposphere
The troposphere is the layer of the atmosphere where most of the Earth’s weather phenomena occur. It is characterized by a well-mixed composition, with the following major constituents:
Nitrogen (N2): Approximately 78% by volume
Oxygen (O2): Approximately 21% by volume
Argon (Ar): Approximately 0.93% by volume
Carbon dioxide (CO2): Approximately 0.04% by volume
Water vapor (H2O): Highly variable, typically ranging from 0.01% to 4% by volume
The variable distribution of water vapor in the troposphere is a key driver of weather patterns and the formation of clouds, precipitation, and other atmospheric phenomena.
Studying Tropospheric Temperature Changes
Both the stratosphere and troposphere have been studied using satellite measurements of microwave radiation emitted by oxygen molecules in the atmosphere. The intensity and frequency of the microwave radiation detected by the satellite are related to the temperature and the altitude of the oxygen molecules.
By measuring the intensity at different frequencies, the microwave measurements can be used to work out how temperature changed at different altitudes in the atmosphere. This technique has been employed to study long-term changes in atmospheric temperatures, although there are several challenges and limitations that must be addressed.
Challenges in Assessing Long-Term Atmospheric Temperature Changes
Accurately assessing long-term changes in atmospheric temperatures is a complex task that involves addressing several challenges:
Influence of Surface Temperatures: The measurements of the lower troposphere can be influenced by the surface temperatures, which can complicate the interpretation of long-term trends.
Effects of Stratospheric Cooling: The cooling of the stratosphere can have effects on the measurements of the lower troposphere, requiring careful consideration and adjustments.
Instrument Calibration and Transition: Accurately transferring measurements between different satellite instruments over time can be challenging, as it requires careful calibration and accounting for any changes in instrument characteristics.
Spatial and Temporal Variability: Atmospheric temperatures can exhibit significant spatial and temporal variability, which can make it difficult to extrapolate local or regional measurements to global trends.
Addressing these challenges is crucial for improving our understanding of long-term changes in atmospheric temperatures and their implications for the Earth’s climate system.
References
NASA. (n.d.). Studying Earth’s Stratospheric Water Vapor. Retrieved from https://www.nasa.gov/centers-and-facilities/langley/studying-earths-stratospheric-water-vapor/
ScienceDirect. (n.d.). Stratosphere. Retrieved from https://www.sciencedirect.com/topics/earth-and-planetary-sciences/stratosphere
Met Office. (n.d.). Upper Air. Retrieved from https://climate.metoffice.cloud/upper_air.html
Tsunamis are one of the most destructive natural disasters, capable of causing widespread devastation and loss of life. These massive waves, triggered by events such as underwater earthquakes, volcanic eruptions, or landslides, can travel at high speeds across the ocean and inundate coastal regions with tremendous force. In this comprehensive guide, we will delve into the science behind tsunamis, explore some of the most devastating events in history, and discuss the efforts to mitigate the risks associated with this natural phenomenon.
The Science of Tsunamis
Tsunamis are generated by the displacement of a large volume of water, typically in an ocean or a large lake. This displacement can be caused by a variety of factors, including:
Underwater Earthquakes: The sudden movement of tectonic plates beneath the ocean floor can displace a massive amount of water, triggering a tsunami. The 2004 Indian Ocean tsunami and the 2011 Tohoku tsunami in Japan were both caused by powerful undersea earthquakes.
Volcanic Eruptions: Volcanic activity, such as the eruption of an underwater volcano or the collapse of a volcanic island, can also generate a tsunami. The 1883 eruption of Krakatoa in Indonesia is a prime example of this.
Landslides: Massive underwater landslides, often triggered by earthquakes or volcanic activity, can displace a large volume of water and create a tsunami.
The physics behind tsunami propagation can be described by the following equations:
Wave Speed: The speed of a tsunami wave is determined by the depth of the water, as described by the equation: $c = \sqrt{gh}$, where $c$ is the wave speed, $g$ is the acceleration due to gravity, and $h$ is the water depth.
Wave Height: The height of a tsunami wave is influenced by the magnitude of the initial displacement and the bathymetry (underwater topography) of the seafloor. The wave height can be estimated using the equation: $H = \frac{A}{d}$, where $H$ is the wave height, $A$ is the initial displacement, and $d$ is the water depth.
Wave Energy: The energy of a tsunami wave is proportional to the square of the wave height, as described by the equation: $E = \frac{1}{2}\rho gH^2$, where $E$ is the wave energy, $\rho$ is the density of water, and $H$ is the wave height.
These equations and principles help scientists understand the complex dynamics of tsunami propagation and the factors that contribute to their devastating impact.
Devastating Tsunami Events in History
Throughout history, there have been numerous instances of tsunamis causing catastrophic damage and loss of life. Here are some of the most devastating events:
2004 Indian Ocean Tsunami: This tsunami, triggered by a magnitude 9.1 earthquake off the coast of Sumatra, Indonesia, resulted in the deaths of over 227,898 people across 14 countries. The total estimated material losses in the Indian Ocean region were $10 billion, and the insured losses were $2 billion.
1960 Valdivia Earthquake and Tsunami: The 1960 Valdivia earthquake in Chile, with a magnitude of 9.5, is the largest earthquake ever instrumentally recorded. It generated a tsunami that was destructive not only along the coast of Chile but also across the Pacific in Hawaii, Japan, and the Philippines. The earthquake caused an estimated 490-5,700 fatalities, and the tsunami resulted in 61 deaths in Hawaii, 139 deaths in Japan, and at least 21 deaths in the Philippines.
2011 Tohoku Earthquake and Tsunami: The 2011 Tohoku earthquake, with a magnitude of 9.0, triggered a tsunami that reached approximately 6 miles inland and 133 feet above sea level. The tsunami resulted in the deaths of over 16,000 people and caused billions of dollars in damage to infrastructure, including major damage to the Fukushima nuclear power plant.
1896 Meiji-Sanriku Tsunami: This tsunami, triggered by a magnitude 8.5 earthquake off the coast of Japan, resulted in the deaths of over 22,000 people. The wave heights reached up to 125 feet (38 meters) in some areas, making it one of the deadliest tsunamis in Japanese history.
1883 Krakatoa Eruption and Tsunami: The eruption of the Krakatoa volcano in Indonesia in 1883 generated a series of tsunamis that caused widespread destruction and the deaths of over 36,000 people. The tsunamis were caused by the collapse of the volcanic island and the resulting displacement of a large volume of water.
These events highlight the immense power and devastating impact of tsunamis, underscoring the importance of understanding their underlying mechanisms and developing effective mitigation strategies.
Mitigating the Risks of Tsunamis
In order to reduce the devastating effects of tsunamis, various efforts have been made to improve our understanding of these natural disasters and develop effective early warning systems.
Tsunami Monitoring and Forecasting: Agencies such as the National Oceanic and Atmospheric Administration (NOAA) and the Intergovernmental Oceanographic Commission (IOC) operate global tsunami monitoring and forecasting systems. These systems use a network of seismic and sea-level sensors to detect and track the propagation of tsunami waves, allowing for timely warnings to be issued.
Tsunami Early Warning Systems: Many countries have implemented tsunami early warning systems, which use a combination of seismic and sea-level data to detect the occurrence of a tsunami and issue alerts to coastal communities. These systems aim to provide sufficient time for evacuation and preparedness measures.
Coastal Infrastructure and Mitigation Measures: Coastal communities have implemented various infrastructure and mitigation measures to reduce the impact of tsunamis. These include the construction of seawalls, breakwaters, and tsunami shelters, as well as the development of evacuation plans and public awareness campaigns.
NASA’s Role in Tsunami Research and Mitigation: NASA’s expertise and access to Earth-observing data are valuable tools in understanding the mechanisms behind tsunamis and supporting research to improve local tsunami forecasting and early warning systems. NASA’s Applied Sciences program collaborates with various agencies to develop innovative solutions for disaster management, including the mitigation of tsunami risks.
Numerical Modeling and Simulation: Advances in computational power and numerical modeling techniques have enabled scientists to develop sophisticated simulations of tsunami propagation and inundation. These models help researchers and policymakers better understand the potential impacts of tsunamis and inform the development of effective mitigation strategies.
Tsunami Preparedness and Education: Educating coastal communities about tsunami risks, evacuation procedures, and emergency response plans is crucial for saving lives. Public awareness campaigns, disaster drills, and community-based preparedness programs play a vital role in enhancing resilience to these natural disasters.
By leveraging scientific knowledge, technological advancements, and collaborative efforts, the global community is working to mitigate the devastating impacts of tsunamis and save lives in the face of this formidable natural calamity.
Conclusion
Tsunamis are among the most destructive natural disasters, capable of causing widespread devastation and loss of life. Understanding the science behind their formation, propagation, and impact is crucial for developing effective mitigation strategies. Through advancements in monitoring, forecasting, early warning systems, and coastal infrastructure, the global community is working to reduce the devastating effects of these powerful waves. By combining scientific knowledge, technological innovations, and community-based preparedness, we can strive to build a more resilient and safer world in the face of this formidable natural calamity.
