About liver

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1. Introduction:

Liver is the largest organ in the human body which weighs 2% of it [1]. Liver is the main key organ of the human body, characterized in reddish brown color. It is located on the right side of the abdominal cavity underneath the diaphragm [2]. Liver is protected by costal cartilage of the ribs. It is strategically placed to receive venous blood from the portal vein, before passing it back to the heart [3]. It is the first organ which exposed to absorb nutrients, drugs, metals, environmental toxicants and metabolic by products of bacteria present in the gastrointestinal tract [4]. It performs more than 400 functions everyday to keep body healthy [5]. It has two major sources which supplies blood to the liver; first one is Oxygenated blood flows in from the hepatic artery, and the second is Nutrient-rich blood flows in from the portal vein [6]. Liver holds the 13% of the body's blood supply at any given moment.

Liver has two large sections, right lobe and left lobes, which are made up of thousands of lobules. Left lobe is smaller than right lobe which is further divided in to caudate and quadrate lobes. Its undersurface is so irregular because this visceral surface is in contact with the lower esophagus, the stomach, the right kidney and the adrenal gland. It has a gallbladder which sits underneath the liver, along with parts of the pancreas and intestines [7].

2.1. Structure of the liver:

By looking the structure of liver we can say what comes in and what goes out:

Dr. Manoj Kumar Sharma MD,DM and Dr. Praveen Sharma MD, DM, The Institute of Liver and Biliary Sciences, New Delhi, India

In:

  • Portal vein
  • Hepatic artery

Out:

  • Hepatic vein
  • Bile duct
  • Lymph

2.1.1. Portal vein:

Portal vein is also called as Hepatic portal vein. It is located in the abdominal cavity which drains blood from the spleen and gastrointestinal tract.

2.1.2. Hepatic artery:

In human anatomy, the hepatic artery is a short blood vessel which supplies oxygenated blood to the liver, pylorus, a part of small intestine and pancreas.

2.1.3. Bile Duct:

Bile duct is also called as Common Bile duct. It looks like a tube anatomic structure in a human gastrointestinal tract. Bile is required to digest the food, and is excreted by the liver into the passage, it carries the bile toward the hepatic duct, and it joins with cystic duct to form the common bile duct.

2.1.4. Hepatic vein:

Here the blood vessels that drains the deoxygenated blood from the liver, and cleaning the blood from small intestine and colon in to the inferior vena cava.

The internal structure of the liver is fully based on the arrangements of liver cells in to a lobule. The lobule is composed of liver cells, as well as liver sinusoids lined with endothelial bile passageways and, at the lobule's periphery, blood vessels. The liver has two incoming vessels, portal vein and hepatic artery. It forms as a branched network to deliver blood to the primary functional unit (the liver lobule).The gateway veins, hepatic arteries and fury ducts run beside each other, until they reach the lobule where they connect to the sinusoids. The structure at this point is the portal tract. Each portal tract has a portal vein delivering venous blood and a hepatic artery delivering oxygenated blood [8]. All these combined to flow the fine blood vessels (sinusoids). The centre of the lobule has a hepatic venule draining the sinusoids into the hepatic veins and finally to the inferior vena cava. [9]

2.2. Gallbladder:

A structure which looks like a pear lies on the under or visceral surface of the liver. It is called the gallbladder and it is composed of three portions, they are neck, the body, and the fundus. The inner lining of the gallbladder resembles somewhat that of the stomach with its rugae and is composed of mucous membranes. It concentrates stores and evacuates bile. It has a mucosa in large folds separated by crypts which may extend to the deepest muscular layers;the gallbladder has a capacity of approximately 50 ml of bile. This structure receives its arterial supply from the cystic artery while the cystic vein drains the gallbladder directly into the portal vein. It should be remembered that the cystic artery is a branch of the right hepatic artery. The gallbladder receives its nerve supply via the celiac plexus. [10]

2.3. Functions of the liver:

Liver is the only organ which uses the food to make all nutrients for essential functions of the human body [11]. Bile is formed by the liver cells, and excreted into tiny bile canaliculi located between the cells. This helps to emulsification of fat and preparing them to digestion and absorption. Blood circulates from the stomach and intestines' passes through the liver; here liver processes that blood and stores the nutrients in the liver and releases whenever it is needed [12]. Liver has some more functions, they are [13]:

  • Producing the bile, it helps to carry away waste and break down fats in the small intestine during digestion.
  • Blend of plasma proteins.
  • Production of cholesterol and special proteins to help carry away fats through the body.
  • Conversion of glucose into glycogen for storage (This glycogen can later be converted back to glucose for energy).
  • Maintenance of blood levels of amino acids, which form the building blocks of proteins.
  • Dispensation of hemoglobin in order to use the iron content in it.
  • Exchange of toxic ammonia to urea (Urea is one of the ending goods of protein metabolism that is excreted in the urine.)
  • Clearing the blood of drugs and other poisonous substances
  • Production of clotting factors.
  • Resisting infections by adopting protected factors and removing microorganisms from the bloodstream.
  • Variable hormone stability.
  • Storing of nutrients for various processes.

2.4. Dimensions of the Liver:

Here by looking a systematic review of liver histology in a series of normal adult human liver biopsy samples to generate a database for statistical analysis. Particular attention was paid to the overall length of the biopsy and the numbers and dimensions of portal tract structures.

The average aggregate length of the liver tissue was 1.8 ± 0.8 cm (area of 16.4 ± 10.7 mm2), representing 7 ± 3 tissue fragments. [14]

The average minimum external diameter of interlobular

Bile ducts was 13 ± 4 µm,

Of hepatic arteries 12 ± 5 µm,

Normal portal vein size [15][16]:

Age < 10 yrs diameter is 8.5 ± 2.7

Age >10 yrs diameter is 10±2

3. PRO/ENGINEER:

Product design firms and manufacturing companies are under constant pressure to develop more products in less time, without sacrificing innovation or quality. As a solution for the above, PTC (Parametric Technology Corporation) which was founded by Samuel Peisakhovich Geisberg, launched Pro/ENGINEER in 1988. Since 1985, PTC has provided superior clients, acquired key companies, and formed industry-leading goods to fetch you the top in invention expansion software. Parametric Technology Corporation (PTC) delivers the broadest range of powerful product development packages - industry's fastest, most comprehensive tools: easy to use, competitively priced, and always upgradeable - to seamlessly meet the varied demands of your business.

PTC became the first to release a pure Internet architecture solution for product data management and collaboration with Wind chill. Today, PTC positions their six core product families (Pro/ENGINEER, Wind chill, Arbor text, MathCAD, Product View, and Co Create) into one suite that they call the Product Development System. Pro/ENGINEER is an integral part of a broader product development system developed by PTC. It seamlessly connects to PTC's other solutions including Wind chill, Product View, MathCAD and Arbor text.

Pro/ENGINEER is a parametric, integrated 3D CAD/CAM/CAE solution to allow you to design faster than ever, while maximizing innovation and quality to ultimately create exceptional products. It was the primary victorious, parametric, feature-based, associative solid modeling software on the market. The application runs on Microsoft Windows and UNIX platforms, and provides Solid Modeling, Assembly Modeling, Drafting, Surfacing, Rendering, Data Interoperability, Routed Systems Design, Simulation, Finite Element Analysis, Tolerance Analysis, and NC and Tooling Design functionality. The parametric modeling approach uses parameters, dimensions, features, and relationships to capture intended product behavior and create a recipe which enables design automation and the optimization of design and product development processes. This powerful and rich design approach is used by companies whose product strategy is family-based or platform-driven, where a prescriptive design strategy is critical to the success of the design process by embedding engineering constraints and relationships to quickly optimize the design, or where the resulting geometry may be complex or based upon equations. Pro/ENGINEER provides a complete set of design, analysis and manufacturing capabilities on one, integral, scalable platform.

Companies use Pro/ENGINEER to create a complete 3D digital model of their products. The models consist of 2D and 3D solid model data which can also be used downstream in finite element analysis, rapid prototyping, tooling design, and CNC manufacturing. All data is associative and interchangeable between the CAD, CAE and CAM modules without conversion. A product and its entire bill of materials (BOM) can be modeled accurately with fully associative engineering drawings, and revision control information. The associatively in Pro/ENGINEER enables users to make changes in the design at any time during the product development process and automatically update downstream deliverables. This capability enables concurrent engineering — design, analysis and manufacturing engineers working in parallel — and streamlines product development processes.

3.1. Features & Benefits of Pro/ENGINEER:

  • Powerful, parametric design capabilities allow superior product differentiation and manufacturability.
  • Completely included applications permit you to expand the whole thing from idea to manufacturing within one purpose.
  • Regular circulation of drawing changes to all downstream deliverables allows you to plan with assurance.
  • Absolute effective recreation capabilities allow you to get better product concert and surpass product superiority goals.
  • Computerized creation of associative tooling plan and developed deliverables.

Furthermore, Pro/ENGINEER is easier to use and improves personal productivity by letting users create designs faster using a modern, familiar, consistent user interface. As evidenced through CMMI certification and more stringent QA criteria, PTC's continued commitment to quality ensures that customers get the highest quality release. Pro/ENGINEER is the only CAD software from a major vendor that has achieved a CMMI rating (Level II).

3.2. Pro/ENGINEER Wildfire 4.0:

Pro/ENGINEER Wildfire 4.0 was released in the year 2008. It showcases PTC's continued focus on usability and quality. It offers enhancements that optimize global design processes including electromechanical design. They further improve personal and process productivity. With increased performance and new product design capabilities, Pro/ENGINEER Wildfire 4.0 will take your productivity to a higher level. The following list highlights some of the benefits and new features in Optimize Global Design:

  1. Faster Design: Accelerate your design process with Auto Round. ™Streamline repetitive tasks and reduce the time to create round features on your model. Pro/ENGINEER analyzes the selected edges and then creates an optimal sequence of round features. For a rounding exercise that would take an intermediate user 90 minutes or an expert user 20 minutes to accomplish, Auto Round can complete the entire task in 40 seconds!
  2. Smarter Large Assembly Management: Leverage Automatic Memory Management for fast, on-demand retrieval of the large assemblies and automated selection of required levels of detail for assembly models. You will see up to 40% less memory consumption! The usability of simplified representation preview is also improved with a new Reference Viewer, clearer indication of active components, and the part/ assembly replacement of any component.
  3. Faster Surface Editing: You can now edit surfaces faster and easier by simply picking points on the surface and manipulating the contour and geometry with a drag of the mouse. The surface control point editing allows multi-resolution editing (lightweight editing on dense surfaces), surface smoothing and variable connection transitions, and preservation of surface edits after subsequent boundary edits.
  4. New and Improved Imported Data Utility: Increase reuse of legacy or other CAD data with updated PDF and multiple CAD version updates, including the new Pro/ENGINEER Interface for JT. The Import Data Doctor™ (IDD) enables faster repair of imported geometry and provides visual feedback of the repair process. With the new Feature Recognition Toolkit you can automatically convert imported geometries into parametric features such as holes, protrusions, rounds, chamfers and patterns.
  5. Stunning Visualization: Give “life” to part and assembly models using advanced rendering capabilities to showcase models with spectacular photo-like quality. The improvements in image-based lighting (HDRI-supported), sky lighting, reflections, room snapping, regional rendering, and dynamic texture placement let you highlight the essence of the model in a variety of visual environments.
  6. Smarter 3D Drawings: Increase design information reuse and deliver production ready drawings with the automated display of dimensions in 3D drawings. Organizing the drawing content is also made easier through layer status control in the View Manager, editorial control of multiple annotation types, and tabulation of restricted parameters. You can also publish and access saved 3D drawing views in Product View™.
  7. More CAM Power: Enhancements in NC and tooling design simplify and automate the transformation of engineering designs into manufacturing processes. An easy to use, powerful process manager tool for toolpath definition optimizes toolpath creation and tool selection for maximum product quality and fabrication speed. Annotation features and other new capabilities help you get from art-to-part faster and easier.
  8. Better CAD Data Protection: The Pro/ENGINEER Rights Management Extension can help you protect your valuable intellectual property with market leading digital rights management capabilities. Powered by Adobe® LiveCycle® Rights Management ES, Pro/ENGINEER gives you persistent and dynamic access control of your CAD data, even after it has been removed from a secure vault and distributed to others. Share your design information with confidence and improve your design and manufacturing outsourcing processes.
  9. Faster Electromechanical Design and Collaboration: Ribbon cables can now be automatically created with a few clicks of the mouse. You can also reduce the common errors between electrical designers and mechanical designers when making design changes. The new Pro/ENGINEER ECAD-MCAD Collaboration Extension provides the industry's most advanced collaboration capabilities. You can easily see incremental changes to ECAD and MCAD designs, as well as propose, accept, and reject changes.
  10. Faster Model Analysis: The new Pro/ENGINEER Tolerance Analysis Extension powered by CETOL™ Technology lets you easily analyze geometric variations and tolerance stack-ups-directly in your design environment. Pro/ENGINEER Mechanica makes sophisticated simulation easily accessible to design engineers. Analyze results faster with improved reports and easy results-compare capabilities. Pro/ENGINEER Advanced Mechanica also includes new support for friction-added assemblies and nonlinear, hyper-elastic materials.

3.3 Modules of Pro/ENGINEER Wildfire 4.0:

Six new modules have been introduced with Pro/ENGINEER Wildfire 4.0 and are:

  1. Pro/ENGINEER Tolerance Analysis Extension powered by CETOL Technology — Gives you the power to analyze geometric tolerance stack-ups and gaps. You can quickly analyze and document geometric tolerances directly on the CAD model. With Pro/ENGINEER you can improve your ability to design for manufacturing and easily streamline your detailed design and verification and validation processes.
  2. Pro/ENGINEER Rights Management Extension — Protect your valuable intellectual property with the new, market leading digital rights management capabilities in Pro/ENGINEER. Powered by Adobe Live Cycle Rights Management ES, Pro/ENGINEER lets you secure access to your CAD data to help you improve your design and manufacturing outsourcing processes.
  3. Pro/ENGINEER ECAD-MCAD Collaboration Extension — helps you improve design collaboration between electrical and mechanical designers. Now you can quickly identify changes, cross-highlight changes between MCAD and ECAD applications, and propose/accept/reject changes. Leveraging Pro/ENGINEER and Product View, you can improve your electromechanical detailed design processes, reduce collaboration errors, and get products to market faster.
  4. Pro/ENGINEER Interface for JT — enables you to easily import and export JT parts and assemblies to support multi-CAD design. Pro/ENGINEER Interface for JT translates structure, geometry and visualization information contained within JT files. Whether you need to leverage legacy data or 3rd party CAD data, this new Pro/ENGINEER module helps optimize your detailed design process.
  5. Pro/ENGINEER Manikin Extension — provides a comprehensive digital human modeling solution that will help optimize your product for human-product interactions. You can insert, customize and manipulate manikins inside your product model to gain a better understanding of how the products will be manufactured, used and serviced. Vision cones, reach envelopes and the ability to see the product from the user's perspective the will also give you additional insight into your design.
  6. Pro/ENGINEER Manikin Analysis Extension — Simulate, communicate and optimize manual handling tasks by validating them against published standards and guidelines. This add-on module includes standard algorithms for analyzing workplace tasks including lifting and lowering (NIOSH 81/91), pulling and pushing (Snook), energy expenditure (GARG), and posture (RULA). You can ensure conformance with health and safety guidelines and ergonomic standards.

3.4. Basics in pro-engineer:

The approach of creating three-dimensional features using two-dimensional sketches is an effective way to construct solid models. Many designs are in fact the same shape in one direction. Computer input and output devices we use today are largely two dimensional in nature, which makes this modeling technique quite practical. This method also conforms to the design process that helps the designer with conceptual design along with the capability to capture the design intent. Most engineers and designers can relate to the experience of making rough sketches on restaurant napkins to convey conceptual design ideas. Note that Pro/ENGINEER provides many powerful modeling and design tools, and there are many different approaches to accomplish modeling tasks. The basic principle of feature-based modeling is to build models by adding simple features one at a time.

3.5.Starting the Pro/ENGINEER Software:

How to start Pro/ENGINEER depends on the type of workstation and the particular software configuration you are using. With most Windows and UNIX systems, you may select Pro/ENGINEER on the Start menu or select the Pro/ENGINEER icon on the desktop.

  • Select the Pro/ENGINEER option on the Start menu or select the Pro/ENGINEER icon on the desktop to start Pro/ENGINEER. The Pro/ENGINEER main window will appear on the screen.
  • Click on the new icon, located in the Standard toolbar.
  • In the New dialog box, confirm the model's Type is set to Part (Solid Subtype).
  • Enter Adjuster as the part
  • Turn off the Use default template option.
  • Click on the OK button to accept the settings.
  • In the New File Options dialog box, select EMPTY in the option list to not use any template file.
  • Click on the OK button to accept the settings and enter the Pro/ENGINEER Part Modeling mode.

3.6. General Steps to Create a Part:

In Pro/ENGINEER, the parametric part modeling process involves the following steps:

  • Determine the type of the base feature, the first solid feature, of the design. Note that Extrude, Revolve, or Sweep operations are the most common types of base features.
  • Create a rough two-dimensional sketch of the basic shape of the base feature of the design.
  • Apply/modify constraints and dimensions to the two-dimensional sketch.
  • Transform the two-dimensional parametric sketch into a 3D feature.
  • Add additional parametric features by identifying feature relations and complete the design.
  • Perform analyses/simulations, such as finite element analysis (FEA) or cutter path generation (CNC), on the computer model and refine the design as needed.
  • Document the design by creating the desired 2D/3D drawings.

3.6.1. Units and Basic Datum Geometry Setups

When starting a new model, the first thing we should do is to choose the set of units we want to use:

  • Use the left-mouse-button and select Edit in the pull-down menu area.
  • Use the left-mouse-button and select Setup in the pull-down list. Note that the Pro/ENGINEER menu system is context-sensitive, which means that the menu items and icons of the non-applicable options are grayed out (temporarily disabled).
  • Select the Units option in the Menu Manager window that appeared to the right of the Pro/ENGINEER main window.
  • In the Units Manager - System of Units form, the Pro/ENGINEER default setting Inch lbm Second is displayed. The set of units is stored with the model file when you save.
  • Pick Inch Pound Second (IPS) by clicking in the list window.
  • Click on the Set button to accept the selection.
  • In the Changing Model Units dialog box, click on the OK button to accept the change of the units. Note that Pro/ENGINEER allows us to change model units even after the model has been constructed.
  • Click on the Close button to exit the Units Manager dialog box.
  • Pick done to exit the PART SETUP submenu. Note that the submenu appeared and disappeared as different options were selected, this is known as the tree structure menu system.

3.6.2. Choosing the Datum Plane:

When you start a new part, three datum planes and a coordinate system are added for you. The datum planes are automatically named Front, Top, and Right. The coordinate system indicates the x-, y-, and z-axes. The positive z-axis is perpendicular to the front datum plane. If you orient the datum so the Front plane is flat to the screen, the z-axis is perpendicular to the screen. Datum is points of reference in space that Pro/E uses to calculate distances. Datum can be actual points, planes, or curves, but they have no value for thickness. You will create and place them frequently for a variety of uses in both Part and Assembly modes. Then select the datum plane for sketching.

Pro/ENGINEER provides many powerful tools for model creation. The reference planes can be used as location references in feature constructions.

Move the cursor toward the right side of the main window and click on the Datum Plane Tool icon, then we will get as shown below.

Toolbar buttons for creating DATUMS

Datum planes are infinite planes and they are perpendicular to each other. We can consider three planes as XY, YZ, and ZX planes of a Cartesian coordinate system.

3.6.3.Creating 2D Rough Sketches

Shape Before Size - Creating Rough Sketches

Quite often during the early design stage, the shape of a design may not have any precise dimensions. Most conventional CAD systems require the user to input the precise lengths and location dimensions of all geometric entities defining the design, and some of the values may not be available during the early design stage. With parametric modeling, we can use the computer to elaborate and formulate the design idea further during the initial design stage. With Pro/ENGINEER, we can use the computer as an electronic sketchpad to help us concentrate on the formulation of forms and shapes for the design. This approach is the main advantage of parametric modeling over conventional solid modeling techniques.

As the name implies, rough sketches are not precise at all. When sketching, we simply sketch the geometry so it closely resembles the desired shape. Precise scale or dimensions are not needed. Pro/ENGINEER provides us with many tools to assist in finalizing sketches, known as sections. For example, geometric entities such as horizontal and vertical lines are set automatically. However, if the rough sketches are poor, much more work will be required to generate the desired parametric sketches. Here are some general guidelines for creating sketches in Pro/ENGINEER:

  • Create a sketch that is proportional to the desired shape. Concentrate on the shapes and forms of the design.
  • Keep the sketches simple. Leave out small geometry features such as fillets, rounds, and chamfers. They can easily be placed using the Fillet and Chamfer commands after the parametric sketches have been established.
  • Exaggerate the geometric features of the desired shape. For example, if the desired angle is 85 degrees, create an angle that is 50 or 60 degrees. Otherwise, Pro/ENGINEER might assume the intended angle to be a 90-degree angle.
  • Draw the geometry so that it does not overlap. The sketched geometry should eventually form a closed region. Self-intersecting geometric shapes are not allowed.
  • The sketched geometric entities should form a closed region. To create a solid feature, such as an extruded solid, a closed region section is required so that the extruded solid forms a 3D volume.

Note: The concepts and principles involved in parametric modeling are very different, and sometimes they are totally opposite, to those of the conventional computer aided drafting systems. In order to understand and fully utilize Pro/ENGINEER's functionality, it will be helpful to take a Zen approach to learning the topics presented in this text: Temporarily forget your knowledge and experiences using conventional computer aided drafting systems.

3.6.4. Apply/Modify constraints and dimensions

As the sketch is made, Pro/ENGINEER automatically applies geometric constraints (such as horizontal, vertical and equal length) and dimensions to the sketched geometry. We can continue to modify the geometry, apply additional constraints and/or dimensions, or define/modify the size and location of the existing geometry. It is more than likely that some of the automatically applied dimensions may not match with the design intent we have in mind. For example, we might want to have dimensions identifying the overall-height, overall-width, and the width of the inside cut of the design.

  • Click on the Dimension icon in the Sketcher toolbar as shown. This command allows us to create defining dimensions.
  • Select the inside horizontal line by left-clicking once on the line.
  • Move the graphics cursor below the selected line and click once with the middle mouse- button to place the dimension. (Note that the value displayed on your
  • Screen might be different than what is shown in the above figure.)
  • Select the right vertical line.
  • Place the dimension, by clicking once with the middle-mouse-button at a location toward the right of the sketch.
  • The Dimension command will create a length dimension if a single line is selected.

[Notice the overall-height dimension applied automatically by the Intent Manager is removed as the new dimension is defined.]

[Note that the dimensions that created are displayed with a different color than those that are applied automatically. The dimensions created by the Intent Manager are called weak dimensions, which can be replaced/ deleted as we create specific defining dimensions to satisfy our design intent.]

  • Select the top horizontal line.
  • Select the inside horizontal line.
  • Place the dimension, by clicking once with the middle-mouse-button, at a location in between the selected lines.
  • When two parallel lines are selected, the Dimension command will create a dimension measuring the distance in between.
  • Examine the established dimensions and constraints in the sketch that you have created, is the sketch fully described? Or should we add additional dimensions

3.6.5. Modifying the dimensions of the sketch

  • Click on the Select icon in the Sketcher toolbar. The Select command allows us to perform several modification operations on the sketched geometry and dimensions.
  • Select the overall height dimension of the sketch by double-clicking with the left mouse-button on the dimension text.
  • In the dimension value box, the current length of the line is displayed. Enter new value for the dimension.
  • Press the ENTER key once to accept the entered value.

Pro/ENGINEER will update the sketch using the entered dimension value. Since the other dimensions are much larger, the sketch becomes greatly distorted. We will take a different approach to modify the geometry.

  • Click on the Undo icon in the Standard toolbar to undo the Modify Dimension performed.
  • Notice that the Redo icon is also available in the Standard toolbar.
  • In the pull-down menu area, click on Edit to display the option list and select the following option items:
  • Edit àSelectà All (Note that Crtl+Alt+A can also activate this option.)
  • In the Sketcher toolbar, click on the Modify icon.

With the pre-selection option, all dimensions are selected and listed in the Modify Dimensions dialog box.

  • Turn off the Regenerate option by left-clicking once on the option.
  • On your own, adjust the dimensions. Note that the dimension selected in the Modify Dimensions dialog box is identified with an enclosed box in the display area.
  • Inside the Modify Dimensions dialog box, click on the Accept button to regenerate the sketched geometry and exit the Modify Dimensions command.

Repositioning Dimensions

Confirm the Select icon, in the Sketcher toolbar, is activated.

Press and hold down the left-mouse-button on any dimension text, then drag the dimension to a new location in the display area. (Note the cursor is changed to a moving arrow icon during the operation.)

3.6.6. Geometric Constraint Symbols:

Pro/ENGINEER displays different visual clues, or symbols, to show you alignments, perpendicularities, tangencies, etc. These constraints are used to capture the design intent by creating constraints where they are recognized. Pro/ENGINEER displays the governing geometric rules as models are built.

V Vertical indicates a segment is vertical

H Horizontal indicates a segment is horizontal

L Equal Length indicates two segments are of equal length

R Equal Radii indicates two curves are of equal radii

T Tangent indicates two entities are tangent to each other

≈ Parallel indicates a segment is parallel to other entities

┴ Perpendicular indicates a segment is perpendicular to other entities

è ß Symmetry indicates two points are symmetrical

0 Point on Entity indicates the point is on another entity

After completing the sketch, we should check the diagram is fully constrained.

3.6.7. Completing the Base Solid Feature

Now that the 2D sketch is completed, we will proceed to the next step that is creating a 3D part from the 2D section. Extruding a 2D section is one of the common methods that can be used to create 3D parts. We can extrude planar faces along a path. In Pro/ENGINEER, the default extrusion direction is perpendicular to the sketching plane, DTM2.

Sketched Features (extrusions, revolves, sweeps, blends,) these features require the definition of a two-dimensional cross section which is then manipulated into the third dimension. Although they usually use existing geometry for references, they do not specifically require this. These features will involve the use of an important tool called Sketcher.

The final group of buttons is used for editing and modifying existing features.

  • In the Sketcher toolbar, click Accept to exit the Pro/ENGINEER 2D Sketcher. The 2D sketch is the first element of the Extrude feature definition.
  • In the Feature Option Dashboard, confirm the Depth Value option. This option sets the extrusion of the section by Extrude from sketch plane by a specific depth value.
  • In the depth value box, enter the extrusion depth.
  • In the message area, click Accept to proceed with the creation of the solid feature.
  • Note that all dimensions disappeared from the screen. All parametric definitions are stored in the Pro/ENGINEER database, and any of the parametric definitions can be displayed and edited at any time.

3.7. Pro/ENGINEER Files:

When modeling a part in Pro/ENGINEER, it creates several files. Part files have an extension “.prt.X” where X represents the revision number. Each time a user saves a part, Pro/ENGINEER creates a new file. For instance, a part, say bearing, is saved for the first time; Pro/ENGINEER creates the file - bearing.prt.1. Subsequent saves, it creates “bearing.prt.2”, “bearing.prt.3”, “bearing.prt.4”, and so on. A user can roll back to any previous version of the part by renaming that particular revision file and opening it. For most purposes, the last and latest version is sufficient. The previous versions can be deleted to optimize the disk space by selecting the following list of commands:

FILE à DELETE à OLDER VERSIONS

3.8 Basic Definitions:

  1. Sketching plane - The sketching plane is a reference location where two-dimensional sketches are created. The sketching plane can be any planar part surface or datum plane.
  2. Orientation of the Sketching Plane -To define the orientation of the sketching plane, selects the facing direction of the reference plane with respect to the computer screen. (Although we have selected the sketching plane, Pro/ENGINEER still needs additional information to define the orientation of the sketch plane. Pro/ENGINEER expects us to choose a reference plane (any plane that is perpendicular to the selected sketch plane) and the orientation of the reference plane is relative to the computer screen).
  3. Spline - any one of a series of narrow keys (external splines) formed longitudinally around the circumference of a shaft that fit into corresponding grooves (internal splines) in a mating part: used to prevent movement between two parts, esp in transmitting torque
  4. Extrude - The process of making a shaped object, such as a rod or tube, by forcing a material into a mold
  5. Protrusion - extension beyond the usual limits, or above a plane surface.
  6. Swept blend - Benefits of sweep as well as blend is combined at swept blend feature. Suppose you have multiple sections at different distance of your model and at the same time these multiple section follows a centre curve, then you can think of using swept blend option.
  7. Origin Trajectory - It is used for defining the central trajectory (curve), this can be created in swept blend itself or could be used any earlier created curve.

4. Steps to design the liver:

There are 6 main parts in this liver. They are Liver, Gallbladder, Bile duct, Portal vein, Hepatic artery and Hepatic vein. I have created all these parts separately and assembled them together.

4.1. Steps to create Liver:

Dimensions:

Length = 200 mm (Normal length of liver is between 180 - 220 mm)

Height = 148 mm

  • Start Pro/E Wildfire.
  • * Select à Fileà Newà partà solidà and name the new part [liver].
  • Select Insertà SweepàProtrusion from the menu bar.
  • Select Sketch Traj from the Menu Manager. This will allow you to sketch the trajectory of the sweep.
  • Select the plane labeled FRONT, and select Okay from the DIRECTION menu in the Menu Manager.
  • Select Default from SKET VIEW. Pro/E will switch to Sketcher Mode.
  • Select SketchàIntent Manager from the menu bar.
  • Draw the path using spline
  • Select Spline à Draw 1st profile on the work area à Right click and select toggle
  • Section to draw 2nd profile
  • Select Spline à Draw 2nd profile on the work area à Right click and select toggle
  • Section to draw 3rd one
  • Select Spline à Draw 3rd profile on the work à Right click and select toggle
  • Section to draw 4th one
  • o Select Spline à Draw 4th profile on the work à Right click and select toggle
  • Section to draw 5th one
  • Select spline à Draw 5th profile on the workà Right click and select toggle
  • Click on the right click button (which will be in Pro-Engineer sketcher window)
  • Select the regenerate from the sketcher menu.
  • Modify the dimensions of the liver.
  • Here we need to check it is constrained or not.
  • Select [Done] from the SKETCHER menu.
  • Select the Extrude Tool icon from the tool bar at the right of the screen
  • Select the plane labeled FRONT. This will allow you to sketch in the xy plane and extrude in the z direction. There we need to enter the depth as required. And click ok. Then you will be getting final sketch of the liver.

4.2. Steps to create Gall bladder

Dimensions:

Length = 100 mm

Diameter = 40 mm

  • Start Pro/E Wildfire.
  • * Select à Fileà Newà partà solidà and name the new part [Gall Bladder].
  • Select the Revolve Tool icon from the tool bar at the right of the screen.
  • Select the Sketcher icon from the revolve tool bar on the dashboard.
  • Select the planes labeled FRONT and select the Sketch button in the Section menu.
  • * Select Sketchà Intent Manager from the menu bar.
  • Zoom in so that you see the coordinates.
  • Select Spline from the GEOMETRY menu.
  • Draw it on the work plane with the above dimensions.
  • Choose [Done] from Menu Manager.
  • Select [Regenerate]. All of the dimensions should scale.
  • Click the check button in the revolve tool bar.
  • Rotate the part to examine the modifications.
  • Trim the edges.
  • Select the Extrude Tool icon from the tool bar at the right of the screen

Select the plane labeled FRONT. This will allow you to sketch in the xy plane and extrude in the z direction. Then we will be getting the final sketch of the gall bladder.

4. 3.Steps to create Portal vein

Dimensions:

Diameter for Age < 10 years = 8.5 ± 2.7

> 10 years = 10 ± 2

Start Pro/E Wildfire.

  • Select à Fileà Newà partà solidà and name the new part [Portal Vein].
  • Select Insertà SweepàProtrusion from the menu bar.
  • Select Sketch Traj from the Menu Manager. This will allow you to sketch the trajectory of the sweep.
  • Select the plane labeled FRONT, and select Okay from the DIRECTION menu in the Menu Manager.
  • Select Default from SKETCH VIEW. Pro/E will switch to Sketcher Mode.
  • Select SketchàIntent Manager from the menu bar.
  • Draw the path using spline
  • Select Spline à Draw 1st profile on the work area à Right click and select toggle
  • Section to draw 2nd profile
  • Select Spline à Draw 2nd profile on the work area à Right click and select toggle
  • Click Insert à Swept Blend à Surface to start the Swept Blend Surface tool.
  • In the Swept Blend Options menu manager, choose Select Section, Normal to Origin Trajectory and Done. The Surface: Swept Blend Dialog box should appear.
  • Pick Select Trajectory and then Curve Chain in the following menu manager.
  • After that, select section 1 and choose the location where you want to place the section. Click the start point (on trajectory) to make selection.
  • Next, the sketch button will be activated. Hit the sketch button. You should now enter the sketch mode. Sketch the 1st section for your swept blend.
  • After the Section 1 is defined, the Insert button will be activated now. Hit the Insert button, select the location of section 2 on your trajectory and sketch section 2.
  • Repeat the swept blend option for sketch 2, after that check the tick mark in the dashboard to conform.
  • After completing this we will get the final shape of the portal vein.

4.4. Steps to create Bile duct

Dimensions:

Diameter =13 ± 4 µm

Start Pro/E Wildfire.

Select à Fileà Newà partà solidà and name the new part [Bile Duct].

Repeat the same steps of portal vein to draw the bile duct.(figure 5.4)

4.5. Steps to create Hepatic artery and Hepatic vein

Dimensions:

Diameter of Hepatic artery = 12 ± 5 µm,

Diameter of Hepatic vein = 2.1 mm

Start Pro/E Wildfire.

Select à Fileà Newà partà solidà and name the new part [Hepatic artery and hepatic vein].

Repeat the same steps of portal vein to draw the Hepatic artery and hepatic vein.

4.6. Steps to assemble all the above parts

  1. Start Pro/E Wildfire.
  2. Select Fileà New and choose Assembly under the Type category. Name the assembly [final liver assembly].
  3. You will now begin to add parts to the assembly. Select the Add Component icon from the tool bar at the right of the screen, as shown in Figure 1.
  4. Select the liver part you made.
  5. The Component Placement window will pop up. This window will be used to constrain the part.
  6. Select [Coord Sys] from the pull down menu under the Type category.
  7. Select the part's coordinate system and then the assembly's coordinate system. This will align the part and fully constrain it.
  8. Select Okay from the Component Placement window.
  9. Now you will add the new part. Select the Add Component icon again, and select the part (bile duct) from working directory.
  10. Select [Align] from the Type category in the Component Placement window.Select the bottom surfaces of each support.
  11. Make sure the offset of the constraint in the Component Placement window is set to [Coincident]. If it is not set to [Coincident], double click on it and use the pull-down menu to select [Coincident].
  12. Now select [Mate] from the second pull-down menu in the Type category. Select the front faces of the both (liver and bile duct). So that we can assemble it in liver.(as shown in figure 5.6)
  13. Repeat the same steps for portal vein, hepatic artery and veins, and gall bladder.
  14. Assemble all the above parts by constraining.
  15. After that, we need to modify the appearance of the parts. Select [View] à [Color and Appearance] from the menu bar.
  16. There is currently only one appearance available - the grey shaded coloring of the parts in the assembly. To add more colors and textures, select the plus sign arrow in the Appearance Editor window.
  17. Select the Color icon to alter the color of the new appearance.
  18. A Color Editor window will pop up. Use the R, G, and B slide bars to change the amounts of red, green, and blue to define a new color. Alternatively, you can select a color from the color wheel.
  19. Select the Close button from the Color Editor window when you are satisfied with the new color.We can use the other slide bars in the Appearance Editor window to adjust other properties of the new appearance.
  20. Repeat the process to allow different parts to have different appearances.

6. Problems faced:

  • While designing common bile duct I faced so many problems in using Swept Blend option. Sweeps and blends permit for parts with changeable cross-sections and parts to twist or bend; I resolved those difficulties by selecting the starting point and ending point of that spline, to get a similar diagram with appropriate dimensions.
  • While performing the swept blend option I faced a problem i.e. while choosing the coordinate axis we should be careful in selecting proper axis i.e. choosing the XZ axis instead of XY axis there is a possibility of damage to the design of the part.
  • While drawing bile duct I have encountered the problem, the branch which I tried to attach to the main branch caused me a problem to fix. This is because as per the given dimensions it did not fix, so to overcome the problem of it I have changed the dimensions to fix the problem.
  • I cope with the same problems while drawing the hepatic veins, and hepatic arteries, as well as for portal vein, but I conquer those difficulties.
  • While assembling the final liver diagram I faced a problem assembling the hepatic artery and hepatic veins in to the liver, i.e., it's a bit difficulty aligning the two faces of diagram and as well as while mating them.
  • I faced the same problems while assembling the portal vein, gall bladder, and bile duct, but I triumph over those difficulties.

7. Future Concept:

My future research focuses on design and simulating the fenestrations of liver by using ANSYS Software or by using Lab Window CVI 8.0, conducting the analysis to delivery drug, and escape of biomolecules from gel structure, here we are going to see how the drug flows through the fenestrations, and how it functions.

The most important natural components of a living cell are polymers. Polymers and polymeric gels are representative of “soft materials”. Soft materials are being explored by several researchers, that they can undergo large deformation in response to diverse stimuli, including mechanical stresses, electric fields, and trace amount of enzymes. Some of the examples of soft active materials (SAM) are dielectric elastomers, shape-memory polymers, and stimuli-responsive gels. Stimuli-responsive hydrogels act as actuators to control micro fluidics and adaptive micro lenses. Smart polymers are those that sense the small changes in environment, and adopt themselves to respond to the changes such as temperature, pH, electric field etc., PNIPAAm (Poly (N-isopropylacrylamide)) is one of the polymers that is used for targeted drug delivery because of its biocompatibility and conformable bioavailability to the delivery location with minimum or no side effects. PNIPAAm is a thermo-responsive polymer with a lower critical solution temperature close to body temperature. PNIPAAm Poly (N-isopropylacrylamide) polymer was first synthesized in the 1950s. It is an intensively investigated polymer temperature sensitive polymer which has a simultaneously hydrophobic and hydrophilic structure and demonstrated lower critical solution temperature [LCST] [17] [18]. Since PNIPAAm expels its liquid contents at a temperature near that of the human body, PNIPAAm has been investigated by many researchers for possible applications in controlled drug delivery. PNIPAAm hydrogel has a LCST of 32ºC [19] where as below the LCST the hydrogel is swollen and above the LCST the hydrogel will collapse (shrink). Temperature was increased incrementally for every 15 minutes to ensure that the hydrogel reached the intended experimental temperature. So here, temperature was increased at 0.5°C increments of intervals between 25°C to 43°C. PNIPAAm Hydrogels is under investigation as matrices for the controlled release of bioactive molecules, in particular pharmaceutical proteins, and for the encapsulation of living cells. For these applications, it is often required that the gels degrade under physiological conditions. This means that the originally three-dimensional structure has to disintegrate preferably in harmless products to ensure a good biocompatibility of the hydrogel. In this overview, different chemical and physical cross linking methods used for the design of biodegradable hydrogels are summarized and discussed. Chemical cross linking is a highly versatile method to create hydrogels with good mechanical stability. However, the cross linking agents used are often toxic compounds, which have been extracted from the gels before they can be applied. Moreover, cross linking agents can give unwanted reactions with the bioactive substances present in the hydrogel matrix. Such adverse effects are avoided with the use of physically cross linked gels [20]. PNIPAAm hydrogels are very attractive for applications in sustained and targeted drug delivery systems. As the release of drugs is related to the swelling behavior of hydrogels, the swelling kinetic studies become of great importance to appreciate the release kinetic from hydrogels matrices and investigation of swelling [5].The kinetic parameters of the swelling performed at different temperatures and pHs for hydrogels samples with different mixing ratios of the components. The results obtained by swelling kinetics investigation will show the decrease of the swelling rate constant with increasing temperature.

8. References:

  1. Department of Cell Biology and Histology; Institute of Medical Biology, Department of Orthopaedic.Surgery, Institute of Clinical Medicine, University of Tromsø, 9037 Tromsø, Norway.
  2. STEP PERSPECTIVE, Volume 7, No. 2 -Summer/1995; A Publication of the Seattle Treatment Exchange,Vic Hernandez, Dr.P.H.
  3. From University of Otago, Christchurch Liver Sieve group c 2000.
  4. Moslen, 1996; Haussinger, 1996.
  5. From North Carolina state University, electrical and computer engineering group.
  6. From children's hospitals of Pittsburgh, of UPMC.
  7. Netter F.Atlas of Human Anatomy, 3rd edition, Saunders, 2002.YoungB,Wheather's Functional Histology, 4th edition, Churchill Livingstone, 2000.
  8. Henry Gray(1821-1865).Anatomy of the Human Body.1918.
  9. Fraser R, Day WA, Dobbs BR, Jamieson HA, Cogger VC, Hilmer SN, Warren A, Le Couteur DG,University of Otago, Christchurch, New Zealand and University of Sydney, Concord, Australia.
  10. From North Carolina state University, electrical and computer engineering group.
  11. Dr. Manoj Kumar Sharma MD,DM and Dr. Praveen Sharma MD, DM, The Institute of Liver and Biliary Sciences, New Delhi, India.
  12. Children's Hospital of Pittsburgh of UPMC Hillman Center for Pediatric Transplantation, by Kimberly haberman.
  13. Aleta R. Crawford1, Xi-Zhang Lin2, and James M. Crawford1.
  14. From the 1 Program in Gastrointestinal Pathology, Yale University School of Medicine and Yale Liver Center New Haven, CT; and the 2 Department of Medicine, National Cheng Kung University, Taiwan.
  15. . Patriquin HB, Perreault G, Grignon A, et al. Normal portal venous diameter in children. Pediatric Radiol 1990; 20: 451-453.
  16. 2. Weinreb J, Kumari S, Phillips G, Pochaczevsky R. Portal vein measurements by real-time sonography. AJR 1982; 139(3):497-499.
  17. 17. 1. Heskins, M. and Guillet, J. E.; Journal of Macromolar Science-Chemistry, 8 (1968), A2, p.1441-1455.
  18. Schild, H. G.; Progress in Polymer Science, 2 (1992), 17, p.163-249.
  19. Dhara D, Chatterji PR. Phase transition in linear and cross-linked poly(N-isopropylacrylamide) in water: effect of various type of additives. J Macromol Sci Rev Macromol Chem Phys 2000; C40:51-68.
  20. Advanced Drug Delivery Reviews, Volume 54, Issue 1, 17 January 2002, Pages 13-36.

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