Hornbostel–Sachs or Sachs–Hornbostel is a system of musical instrument classification devised by Erich Moritz von Hornbostel and Curt Sachs, first published in the Zeitschrift für Ethnologie in 1914. An English translation was published in the Galpin Society Journal in 1961, it is the most used system for classifying musical instruments by ethnomusicologists and organologists. The system was updated in 2011 as part of the work of the Musical Instrument Museums Online Project. Hornbostel and Sachs based their ideas on a system devised in the late 19th century by Victor-Charles Mahillon, the curator of musical instruments at Brussels Conservatory. Mahillon divided instruments into four broad categories according to the nature of the sound-producing material: an air column. From this basis and Sachs expanded Mahillon's system to make it possible to classify any instrument from any culture. Formally, the Hornbostel–Sachs is modeled on the Dewey Decimal Classification for libraries, it has five top-level classifications, with several levels below those, adding up to over 300 basic categories in all.

The top five levels of the scheme are as follows: Idiophones produce their sounds by means of the actual body of the instrument vibrating, rather than a string, membrane, or column of air. In essence, this group includes all percussion instruments apart from drums, as well as some other instruments. In the Hornbostel–Sachs classification, idiophones are first categorized according to the method used to play the instrument; the result is four main categories: struck idiophones, plucked idiophones, friction idiophones, blown idiophones. These groups are subsequently divided through various criteria. In many cases these sub-categories are split in singular sets of instruments; the latter category includes the xylophone, the marimba, the glockenspiel, the glass harmonica. These idiophones are set in vibration by being struck, for example xylophones; the player himself/herself executes the movement of striking. It is definitive that the player can apply clear, individual strokes, that the instrument itself is equipped for this kind of percussion.

111.1 Concussion idiophones or clappers – Two or more complementary sonorous parts are struck against each other. 111.11 Concussion stick clappers. 111.12 Concussion plaques or plaque clappers. 111.13 Concussion troughs or trough clappers. 111.14 Concussion vessels or vessel clappers. 111.141 Castanets – Natural and hollowed-out vessel clappers. 111.142 Cymbals – Vessel clappers with manufactured rim. 111.2 Percussion idiophones – The instrument is struck either with a non-sonorous object or against a non-sonorous object. 111.21 Percussion sticks. 111.211 Individual percussion sticks. 111.212 Sets of percussion sticks in a range of different pitches combined into one instrument. -- All xylophones, as long. 111.22 Percussion plaques. 111.221 Individual percussion plaques. 111.222 Sets of percussion plaques – Examples are the lithophone and most metallophones. 111.23 Percussion tubes. 111.231 Individual percussion tubes. 111.232 Sets of percussion tubes. 111.24 Percussion vessels. 111.241 Gongs – The vibration is strongest near the vertex.

111.241.1 Individual gongs. 111.241.2 Sets of gongs. 111.242 Bells – The vibration is weakest near the vertex. 111.242.1 Individual bells. 111.242.11 Resting bells whose opening faces upward 111.242.12 Hanging bells suspended from the apex. 111.242.121 Hanging bells without internal strikers. 111.242.122 Hanging bells with internal strikers. 111.242.2 Sets of bells or chimes. 111.242.21 Sets of resting bells whose opening faces upward. 111.242.22 Sets of hanging bells suspended from the apex. 111.242.221 Sets of hanging bells without internal strikers. 111.242.222 Sets of hanging bells with internal strikers. 111.3 Mixed sets of directly struck idiophones The player himself/herself does not go through the movement of striking. 112.1 Shaken Idiophones or rattles – The player makes a shaking motion 112.11 Suspension rattles – Perforated idiophones are mounted together, shaken to strike against each other. 112.111 Strung rattles – Rattling objects are strung in rows on a cord. 112.112 Stick rattles – Rattling objects are strung on a bar or ring.

112.12 Frame rattles – Rattling objects are attached to a carrier against which they strike. 112.121 Pendant rattles. 112.122 Sliding rattles. 112.13 Vessel rattles – Rattling objects enclosed in a vessel strike against each other or against the walls of the vessel, or against both. 112.2 Scraped Idiophones – The player causes a scraping movement directly or indirectly. This group must not be confused with that of friction idiophones. 112.21 Scraped sticks. 112.211 Scraped sticks without resonator. 112.212 Scraped sticks with resonator. 112.22 Scraped tubes. 112.221 Scraped tubes without resonator. 112.222 Scraped tubes with resonator. 112.23 Scraped vessels. 112.231 Scraped vessels without resonator. 112.232 Scraped vessels with resonator. 112.24 Scraped wheels – cog rattles or Ratchet 112.241 Scraped wheels without resonat

Coincident disruptive coloration

Coincident disruptive coloration or coincident disruptive patterns are patterns of disruptive coloration in animals that go beyond the usual camouflage function of breaking up the continuity of an animal's shape, to join up parts of the body that are separate. This is seen in extreme form in frogs such as Afrixalus fornasini where the camouflage pattern extends across the body and all four limbs, making the animal look quite unlike a frog when at rest with the limbs tucked in. A special case is the disruptive eye mask that camouflages the most conspicuous feature of many animals, the eye; the English zoologist and camouflage expert Hugh Cott explained, while discussing "a little frog known as Megalixalus fornasinii" in the chapter on coincident disruptive coloration in his 1940 book Adaptive Coloration in Animals, that It is only when the pattern is considered in relation to the frog's normal attitude of rest that its remarkable nature becomes apparent... The attitude and striking colour-scheme thus combine to produce an extraordinary effect, whose deceptive appearance depends upon the breaking up of the entire form into two contrasted areas of brown and white.

Considered separately, neither part resembles part of a frog. Together in nature the white configuration alone is conspicuous; this stands out and distracts the observer's attention from the true form and contour of the body and appendages on which it is superimposed. Cott concluded that the effect was concealment "so long as the false configuration is recognized in preference to the real one"; the effect is seen in the common frog, Rana temporaria, in which the dark and light bands that cross the body and hind legs coincide in the resting position, in several moths such as the oak beauty, Biston strataria, in which the forewing pattern coincides with the pattern on the narrow strip of the hindwing, visible in the moth's habitual resting position. Cephalopods are capable by day used for signalling as well as camouflage; the effect was tested in two experiments in 2009 by Aron Székely. One form of coincident disruptive coloration has special importance. Disruptive eye masks camouflage the eyes of a variety of animals, both invertebrates such as grasshoppers and vertebrates such as fishes, frogs and snakes.

The eye has a distinctive shape and dark coloration dictated by its function, it is housed in the vulnerable head, making it a natural target for predators. It can be camouflaged by a suitable disruptive pattern arranged to run up to or through the eye, such as the camouflage eyestripe of the Mexican vine snake and certain fishes. In the words of the camouflage researchers Innes Cuthill and A. Székely, Cott's book provided "persuasive arguments for the survival value of coloration, for adaptation in general, at a time when natural selection was far from universally accepted within evolutionary biology." In particular, they argued, Cott's category of "Coincident Disruptive Coloration" "made Cott's drawings the most compelling evidence for natural selection enhancing survival through disruptive camouflage." Such patterns embody, as Cott stressed, considerable precision as the markings must line up for the disguise to work. Cott's description and in particular his drawings convinced biologists that the markings, hence the camouflage, must have survival value.

Military building

A military building is any structure designed to house functions performed by a military unit. General types include: Administrative Facilities Ammunition Storage Facilities Commissary Facilities Correctional Facilities Fortifications Hospitals Housing Mess Military Intelligence Facilities Museums POL Storage and Handling Facilities Recreation Facilities Research Facilities Training Facilities Utility Structures Vehicle Repair, Maintenance, & Storage Facilities Weapons and Ammunition Production Facilities Military organizations of all types must support a wide range of administrative functions including personnel management and procurement; some facilities are quite similar to civilian office buildings while others are converted from other military uses and can be quite idiosyncratic. Ammunition is stored in small quantities in reinforced structures which are separated. Standard designs are sometimes called "igloos". Traditionally, military units provided most of the rations and other supplies needed by most military personnel.

However, modern units provide fewer items and many personnel must buy some items with their own funds. Personnel with families must buy food and other necessities for the family; this has created the need for modern commissary and “PX” buildings. In some cases, these buildings are similar to modern supermarkets. Most military installations have small jails for temporary holding of suspects or short term punishment of minor offenses. However, military organizations have larger, centralized facilities for longer term incarceration of persons convicted of more serious offenses; the main correctional facility of the US Army, Air Force, Marines is the United States Disciplinary Barracks located at Fort Leavenworth, Kansas. Fortifications vary in nature depending on the mission and type of unit engaged. Full-service military hospitals are a recent innovation in military history. Prior to the nineteenth century, military hospitals as we know them today did not exist. Soldiers wounded in combat were treated in the field or in makeshift facilities commandeered near the field of battle.

Medical technology at the time was such that most serious wounds were fatal and, there was little need for facilities that provided for long-term care and recuperation. Battlefield amputations were one of the most common procedures and were only successful in saving the life of the victim in a limited number of cases. However, beginning in the nineteenth and twentieth centuries, advances in blood transfusion, anesthesia and trauma treatment meant that many more soldiers could survive wounds although the treatment time was much longer. Advances in the treatment of infectious diseases meant that many more personnel required treatment for non-combat conditions. All of these conditions, plus an increasing number of personnel with families, have led to the construction of full service military hospitals; these hospitals treat both members of their families. Military housing includes barracks, UOQs, family housing; the age and condition of these facilities varies widely. A few officer family housing units are historical in nature and can be quite large and ornate.

Most family and UOQ housing is now similar in nature to civilian housing stock. In most advanced countries, barracks housing has been modernized, but remnants of housing from World War II and older periods still remains in the inventory. “Mess” is the military term for any facility serving food to large groups. Some mess halls in remote locations can be rudimentary, but others in established locations can be similar to modern cafeterias; these facilities are secured. Modern facilities involve intensive use of electronics and computer technology; because of the role military actions have played in determining world history, military museums are common. They range from small facilities memorializing the actions of local units to large, sophisticated facilities devoted to an entire branch of service or entire wars; these facilities are engineered to provide safe handling of petroleum-based materials. Newer facilities include containments to prevent environmental pollution from due to spills. Recreation facilities for both military personnel and their families.

Athletic facilities are common as are NCO/enlisted personnel clubs. Military organizations conduct extensive research operations and maintain extensive purpose-built research facilities to support those activities. Traditional military training facilities focused on physical conditioning and skills training. Newer facilities make extensive use of computer simulations of various kinds to provide more hours or training in more realistic situations at lower cost and with lower risk to personnel. Military academies are devoted to training military officer cadets. Facilities for advanced training of senior officers exist. Examples include the US Army Command and General Staff College at Ft. Leavenworth, KS. Many military installations are large enough to require their own utility systems. Water treatment plants, sewage treatment plants, electric power generation stations are found on many military installations. Vehicle repair shops can be large and built to accommodate large vehicles. Aircraft hangars are some of the most specialized military buildings.

Production of ammunition is now outsourced to industry contractors. However, facilities such as Sunflower Army Ammunition Plant produced small arms ammunition for the US Military for many years. More exotic facilities such as Rocky Mountain Arsenal was the main facil