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Engineering Specifications
Specifications are needed to avoid errors due to lack of compatibility.

Guidance and content

Sometimes a guide or a standard operating procedure is available to help write and format a good specification.[5][6][7][8] A specification might include:

  • Descriptive title, number, identifier, etc. of the specification

The adult male of the species is up to 4.5 centimeters long, and the adult female may reach 5.5 centimeters. The body of the adult is generally yellow-brown in color and the wings are pale with large brown spots. The nymphs are different in appearance.[1] They change color as they mature and their coloration is a polyphenic trait: one that is influenced by environmental conditions, producing multiple forms from one genotype. This is not uncommon among grasshoppers. In this species, the coloration of the nymphs is especially influenced by temperature. Nymphs are various shades of green, yellow, or red, usually with a pattern of black markings. They are often red at lower temperatures, but at higher temperatures, only green and yellow shades occur. Black patterning is also influenced by temperature, with lower temperatures inducing darker markings. Density is also a common factor in color polyphenism, but it is less important in this species than in many other grasshoppers. Nymphs reared in crowded conditions develop darker black markings, but density has little effect on their background colors.

Construction Specifications

  1. architects
  2. architectural technologists
  3. structural engineers
  4. landscape architects
  5. building services engineers

Engineering is a broad discipline which is often broken down into several sub-disciplines. These disciplines concern themselves with differing areas of engineering work. Although initially an engineer will usually be trained in a specific discipline, throughout an engineer's career the engineer may become multi-disciplined, having worked in several of the outlined areas. Engineering is often characterized as having four main branches:[15][16][17]

Major topics of applied mechanics

The concept of a dynamical system has its origins in Newtonian mechanics. There, as in other natural sciences and engineering disciplines, the evolution rule of dynamical systems is an implicit relation that gives the state of the system for only a short time into the future. (The relation is either a differential equation, difference equation or other time scale.) To determine the state for all future times requires iterating the relation many times—each advancing time a small step. The iteration procedure is referred to as solving the system or integrating the system. If the system can be solved, given an initial point it is possible to determine all its future positions, a collection of points known as a trajectory or orbit.

Before the advent of computers, finding an orbit required sophisticated mathematical techniques and could be accomplished only for a small class of dynamical systems. Numerical methods implemented on electronic computing machines have simplified the task of determining the orbits of a dynamical system.

For simple dynamical systems, knowing the trajectory is often sufficient, but most dynamical systems are too complicated to be understood in terms of individual trajectories. The difficulties arise because:

  • The systems studied may only be known approximately—the parameters of the system may not be known precisely or terms may be missing from the equations. The approximations used bring into question the validity or relevance of numerical solutions. To address these questions several notions of stability have been introduced in the study of dynamical systems, such as Lyapunov stability or structural stability. The stability of the dynamical system implies that there is a class of models or initial conditions for which the trajectories would be equivalent. The operation for comparing orbits to establish their equivalence changes with the different notions of stability.
  • The type of trajectory may be more important than one particular trajectory. Some trajectories may be periodic, whereas others may wander through many different states of the system. Applications often require enumerating these classes or maintaining the system within one class. Classifying all possible trajectories has led to the qualitative study of dynamical systems, that is, properties that do not change under coordinate changes. Linear dynamical systems and systems that have two numbers describing a state are examples of dynamical systems where the possible classes of orbits are understood.
  • The behavior of trajectories as a function of a parameter may be what is needed for an application. As a parameter is varied, the dynamical systems may have bifurcation points where the qualitative behavior of the dynamical system changes. For example, it may go from having only periodic motions to apparently erratic behavior, as in the transition to turbulence of a fluid.
  • The trajectories of the system may appear erratic, as if random. In these cases it may be necessary to compute averages using one very long trajectory or many different trajectories. The averages are well defined for ergodic systems and a more detailed understanding has been worked out for hyperbolic systems. Understanding the probabilistic aspects of dynamical systems has helped establish the foundations of statistical mechanics and of chaos.

Recycling is a process to change waste materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfilling) by reducing the need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to plastic production.[1][2] Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse and Recycle" waste hierarchy. Recyclable materials include many kinds of glass, paper, metal, plastic, textiles, and electronic


A number of different systems have been implemented to collect recyclates from the general waste stream. These systems lie along the spectrum of trade-off between public convenience and government ease and expense. The three main categories of collection are "drop-off centres," "buy-back centres," and "curbside collection".

Manufacturing process management (MPM) is a collection of technologies and methods used to define how products are to be manufactured. MPM differs from ERP/MRP which is used to plan the ordering of materials and other resources, set manufacturing schedules, and compile cost data. A cornerstone of MPM is the central repository for the integration of all these tools and activities aids in the exploration of alternative production line scenarios; making assembly lines more efficient with the aim of reduced lead time to product launch, shorter product times and reduced work in progress (WIP) inventories as well as allowing rapid response to product or product changes.

Topics and technology

Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from their atomic-scale properties. Thus, solid-state physics forms the theoretical basis of materials science. It also has direct applications, for example in the technology of transistors and semiconductors.


Solid materials are formed from densely packed atoms, which interact intensely. These interactions produce the mechanical (e.g. hardness and elasticity), thermal, electrical, magnetic and optical properties of solids. Depending on the material involved and the conditions in which it was formed, the atoms may be arranged in a regular, geometric pattern (crystalline solids, which include metals and ordinary water ice) or irregularly (an amorphous solid such as common window glass). The bulk of solid-state physics, as a general theory and not really a proven form of research, is focused on crystals. Primarily, this is because the periodicity of atoms in a crystal — its defining characteristic — facilitates mathematical modeling. Likewise, crystalline materials often have electrical, magnetic, optical, or mechanical properties that can be exploited for engineering purposes. The forces between the atoms in a crystal can take a variety of forms. For example, in a crystal of sodium chloride (common salt), the crystal is made up of ionic sodium and chlorine, and held together with ionic bonds. In others, the atoms share electrons and form covalent bonds. In metals, electrons are shared amongst the whole crystal in metallic bonding. Finally, the noble gases do not undergo any of these types of bonding. In solid form, the noble gases are held together with van der Waals forces resulting from the polarisation of the electronic charge cloud on each atom. The differences between the types of solid result from the differences between their bonding.

Recycling codes are used to identify the material from which an item is made, to facilitate easier recycling or other reprocessing. Such symbols have been defined for batteries, biomatter/organic material, glass, metals, paper, and plastics.[citation needed]

Symbol Code Description Examples
Plastics (see resin identification code[1])
Plastic-recyc-01.svg #1 PET(E) Polyethylene terephthalate Polyester fibers, soft drink bottles
Plastic-recyc-02.svg #2 PEHD or HDPE High-density polyethylene Plastic bottles, plastic bags, trash cans, imitation wood
Plastic-recyc-03.svg #3 PVC Polyvinyl chloride Window frames, bottles for chemicals, flooring, plumbing pipes
Plastic-recyc-04.svg #4 PELD or LDPE Low-density polyethylene Plastic bags, buckets, soap dispenser bottles, plastic tubes
Plastic-recyc-05.svg #5 PP Polypropylene Bumpers, car interior trim, industrial fibers, carry-out beverage cups
Plastic-recyc-06.svg #6 PS Polystyrene Toys, flower pots, video cassettes, ashtrays, trunks, beverage/food coolers, beer cups, wine and champagne cups, carry-out food containers, Styrofoam
Plastic-recyc-07.svg #7 O (OTHER) All other plastics Polycarbonate (PC), polyamide (PA), styrene acrylonitrile (SAN), acrylic plastics/polyacrylonitrile (PAN), bioplastics
Plastic-recyc-abs.svg #9 or #ABS[citation needed] Acrylonitrile butadiene styrene Monitor/TV cases, coffee makers, cell phones, most computer plastic
Batteries (see also battery recycling)

#8 Lead Lead–acid battery Car batteries

#9 or #19 Alkaline Alkaline battery

#10 NiCD Nickel–cadmium battery

#11 NiMH Nickel–metal hydride battery

#12 Li Lithium battery

#13 SO(Z) Silver-oxide battery

#14 CZ Zinc–carbon battery
Recycling-Code-20.svg #20 C PAP (PCB) Cardboard
Recycling-Code-21.svg #21 PAP Other paper Mixed paper magazines, mail
Recycling-Code-22.svg #22 PAP Paper

#23 PBD (PPB) Paperboard Greeting cards, frozen food boxes, book covers
Recycling-Code-40.svg #40 FE Steel
41 ALU Recycling Code.svg
#41 ALU Aluminium
Biomatter/Organic material
Recycling-Code-50.svg #50 FOR Wood
Recycling-Code-51.svg #51 FOR Cork Bottle stoppers, place mats, construction material
Recycling-Code-60.svg #60 COT Cotton
Recycling-Code-61.svg #61 TEX Jute

#62-69 TEX Other Textiles
Recycling-Code-70.svg #70 GLS Mixed Glass Container/Multi-Part Container
Recycling-Code-71.svg #71 GLS Clear Glass
Recycling-Code-72.svg #72 GLS Green Glass

#73 GLS Dark Sort Glass

#74 GLS Light Sort Glass

#75 GLS Light Leaded Glass Televisions, high-end electronics display glass

#76 GLS Leaded Glass Older televisions, ash trays, older beverage holders

#77 GLS Copper Mixed/Copper Backed Glass Electronics, LCD Display heads, Clocks/Watches

#78 GLS Silver Mixed/Silver Backed Glass Mirrors, formal table settings

#79 GLS Gold Mixed/Gold Backed Glass Computer glass, formal table settings
Composites (80—99)

#81 PapPet Paper + plastic consumer packaging, pet food bags, cold store grocery bags, Icecream containers, cardboard cans, disposable plates
Recycling-Code-84.svg #84 C/PAP (or PapAl) Paper and cardboard / Plastic / Aluminium liquid storage containers, juice boxes, cardboard cans, Cigarette pack liners, gum wrappers, cartage shells for blanks, fireworks colouring material, Tetra Brik.

#87 Card-stock Laminate Biodegradable plastic laminating material, special occasion cards, bookmarks, business cards, flyers/advertising

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