This type of defect can be avoided by proper cooling practices or by changing the chemical composition of the metal. Additional methods of minimising hot tears are not overheating the casting material and increasing the temperature of the mould. Process specific defects
Die casting
In die casting the most common defects are misruns and cold shuts. These defects can be caused by cold dies, low metal temperature, dirty metal, lack of venting, or too much lubricant. Other possible defects are gas porosity, shrinkage porosity, hot tears, and flow marks. Flow marks are marks left on the surface of the casting due to poor gating, sharp corners, or excessive lubricant. Continuous casting
A longitudinal facial crack is a specialized type of defect that only occurs in continuous casting processes. This defect is caused by uneven cooling, both primary cooling and secondary cooling, and includes molten steel qualities, such as the chemical composition being out of specification, cleanliness of the material, and homogeneity. Sand casting
Sand casting has many defects that can occur due to the mould failing. The mould usually fails because of one of two reasons: the wrong material is used or it is improperly rammed.The first type is mould erosion, which is the wearing away of the mould as the liquid metal fills the mould. This type of defect usually only occurs in sand castings because most other casting processes have more robust moulds. The castings produced have rough spots and excess material.
Amblyopia was first described in the 1600s. The condition may make people ineligible to be pilots or police officers. The word amblyopia is from Greek ἀμβλύς amblys, meaning "blunt", and ὤψ ōps, meaning "sight". Signs and symptoms
Many people with amblyopia, especially those who only have a mild form, are not aware they have the condition until tested at older ages, since the vision in their stronger eye is normal. People with amblyopia typically have poor stereo vision, since it requires both eyes. They further may have, on the affected eye, poor pattern recognition, poor visual acuity, and low sensitivity to contrast and motion.Amblyopia is characterized by several functional abnormalities in spatial vision, including reductions in visual acuity, contrast sensitivity function, and vernier acuity, as well as spatial distortion, abnormal spatial interactions, and impaired contour detection. In addition, individuals with amblyopia have binocular abnormalities such as impaired stereoacuity (stereoscopic acuity) and abnormal binocular summation. Also, central vision in amblyopes is more crowded than central vision in normal observers.These deficits are usually specific to the amblyopic eye. Subclinical deficits of the "better" eye have also been demonstrated.People with amblyopia also have problems of binocular vision such as limited stereoscopic depth perception and usually have difficulty seeing the three-dimensional images in hidden stereoscopic displays such as autostereograms. Perception of depth, from monocular cues such as size, perspective, and motion parallax remains normal.