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Landon Torres
Landon Torres

Visual Signal

The simplest attentional task, detecting a cued stimulus in an otherwise empty visual field, produces complex patterns of performance. Attentional cues interact with backward masks and with spatial uncertainty, and there is a dissociation in the effects of these variables on accuracy and on response time. A computational theory of performance in this task is described. The theory links visual encoding, masking, spatial attention, visual short-term memory (VSTM), and perceptual decision making in an integrated dynamic framework. The theory assumes that decisions are made by a diffusion process driven by a neurally plausible, shunting VSTM. The VSTM trace encodes the transient outputs of early visual filters in a durable form that is preserved for the time needed to make a decision. Attention increases the efficiency of VSTM encoding, either by increasing the rate of trace formation or by reducing the delay before trace formation begins. The theory provides a detailed, quantitative account of attentional effects in spatial cuing tasks at the level of response accuracy and the response time distributions.

visual signal

A, High resolution receptive field maps from primate retinal ganglion cells of the four numerically dominant types, obtained by reverse correlation with spatiotemporal noise stimuli. Punctate islands of sensitivity in the receptive fields reveal the locations of individual cone photoreceptors (Field et al., 2010). Stimulation was from the ganglion cell side of the retina, so cone receptive fields reflect inner segment light guide and waveguide properties (Menzel and Snyder, 1975; Snyder, 1975). Scale bars, 15 μm. B, Map of full cone mosaic obtained over the hexagonal recording array. Receptive field data from hundreds of RGCs were combined to fit a model of punctate spatial inputs that maximized the likelihood over recorded spike trains (Field et al., 2010). Intensity at each putative cone location indicates its incremental contribution to likelihood. Brighter cones are generally 1) those detected in the receptive fields of multiple overlapping RGCs, 2) those obtained from receptive fields exhibiting highest signal-to-noise, and 3) those providing strongest input to RGCs. Scale bar, 100 μm.

Communicating. Alerting. Warning! Whatever your need for a visual signal, Edwards is the one-source solution with the industry's broadest line of visual signals. A signal for every signal need. From cranes and conveyors to safety and security, signals that can be both seen and heard.

This information is directed primarily to recreational boaters, but the requirements discussed also apply to operators of vessels engaged in the carrying of six or fewer passengers. The Visual Distress Signal requirements for most commercial vessels are in Title 46 of the Code of Federal Regulations. The requirement to carry visual distress signals became effective on January 1, 1981. This regulation requires all boats when used on coastal waters, which includes the Great Lakes, the territorial seas and those waters directly connected to the Great Lakes and the territorial seas, up to a point where the waters are less than two miles wide, and boats owned in the United States when operating on the high seas to be equipped with visual distress signals.

Must be Coast Guard approved, in serviceable condition and stowed to be readily accessible. If they are marked with a date showing the serviceable life, this date must not have passed. Launchers produced before Jan. 1, 1981, intended for use with approved signals are not required to be Coast Guard Approved.

The purpose of the regulation is to assure that boaters have a way of attracting attention and securing assistance should the need arise. Properly used visual distress signals will also help reduce the time it takes to locate a boat in difficulty when a search is underway. This will reduce the possibility of a minor emergency becoming a tragedy.

No single signaling device is ideal under all conditions and for all purposes. Consideration should therefore be given to carrying several types. For example, an aerial flare can be seen over a long distance on a clear night, but for closer work, a hand-held flare may be more useful.

The distress flag must be at least 3 x 3 feet with a black square and ball on an orange background. It is accepted as a day signal only and is especially effective in bright sunlight. The flag is most distinctive when waved on something such as a paddle or a boat hook or flown from a mast.

The electric distress light is accepted for night use only and must automatically flash the international SOS distress signal, which is three short flashes, three long flashes, and three short flashes. Flashed four to six times each minute, this is an unmistakable distress signal, well known to most boaters. The device can be checked any time for serviceability if shielded from view.

NOTE: An ordinary flashlight is not acceptable since it must be manually flashed and does not normally produce enough candle power. The Regulation States: "No person in-a boat shall display a visual distress signal on water to which this subpart applies under any circumstances except a situation where assistance is needed because of immediate or potential danger to the persons aboard."

Visual distress signals are part of your boat's safety equipment. Check them before you leave harbor. Their intended purpose is to summon help should the need arise. Visual distress signals can only be effective when someone is in a position to see them. Therefore, when employing pyrotechnic devices, do so only when you see or hear a boat or airplane or you are reasonably sure that someone on shore is in position to see your signal and take action. Good judgment is an essential part of successful use of visual distress signals.

All distress signaling devices have both advantages and disadvantages. The most popular, because of cost, are probably the smaller pyrotechnic devices. Pyrotechnics make excellent distress signals, universally recognized as such, but they have the drawback that they can be used only once. Additionally, there is a potential for both injury and property damage if not properly handled.

The hand-held and the floating orange smoke signaling devices are excellent (if not the best) day signals, especially on clear days. Both signals are most effective with light to moderate winds because higher winds tend to keep the smoke close to the water and disperse it which makes it hard to see.

The unwritten law of the sea requires that a mariner come to the aid of a mariner in distress. Therefore, should you see a distress signal, immediate and positive action should be taken. Notify the nearest Coast Guard station or State authority by radio. Channel 9 on CB and Channel 16 on VHF marine radio (156.8 MHz) are recognized distress channels. If you can assist the stricken vessel without endangering yourself, you should. The Federal Boat Safety Act of 1971 contains a "Good Samaritan" clause stating: "Any person ....who gratuitously and in good faith renders assistance at the scene of a vessel collision, accident, or other casualty without objection of any person assisted, shall not be held liable for any act or omission in providing or arranging salvage, towage, medical treatment, or other assistance where the assisting person acts as an ordinary, reasonably prudent man or woman would have acted under the same or similar circumstances."

Flags are also used to signal your need for help. When in distress, a boat should fly an orange flag with a black square and black ball. A man overboard flag, consisting of the letter "O", can be fixed to a staff which is in turn fixed to a life ring.

When you raise your wrist, a blue ring around your Apple Watch screen indicates that AssistiveTouch is turned on. To activate AssistiveTouch, clench your fist twice quickly. You can change the color of this visual signal in Accessibility > AssistiveTouch > Color. Or you can turn the visual signal off by going to Accessibility > AssistiveTouch > Hand Gestures > Activation Gesture.

This unit of study introduces basic and advanced concepts and methodologies in image processing and computer vision. This course mainly focuses on image processing and analysis methods as well as intelligent systems for processing and understanding multidimensional signals such as images, which include basic topics like multidimensional signal processing fundamentals and advanced topics like visual feature extraction and image classification as well as their applications for face recognition and object/scene recognition. It mainly covers the following areas: multidimensional signal processing fundamentals, image enhancement in the spatial domain and frequency domain, edge processing and region processing, imaging geometry and 3D stereo vision, object recognition and face recognition.

The visual system transmits information about fast and slow changes in light intensity through separate neural pathways. We used in vivo imaging to investigate how bipolar cells transmit these signals to the inner retina. We found that the volume of the synaptic terminal is an intrinsic property that contributes to different temporal filters. Individual cells transmit through multiple terminals varying in size, but smaller terminals generate faster and larger calcium transients to trigger vesicle release with higher initial gain, followed by more profound adaptation. Smaller terminals transmitted higher stimulus frequencies more effectively. Modeling global calcium dynamics triggering vesicle release indicated that variations in the volume of presynaptic compartments contribute directly to all these differences in response dynamics. These results indicate how one neuron can transmit different temporal components in the visual signal through synaptic terminals of varying geometries with different adaptational properties.

The process of neurotransmission involves the conversion of electrical signals into the release of a chemical neurotransmitter from the neurons synaptic terminal, and the key trigger for this release is a rise in calcium concentration. Accordingly, the amplitude and speed of this calcium signal controls the amplitude and time-course of synaptic communication. Working on the synaptic terminals of fish retinal bipolar cells, we show that the presynaptic calcium signal and the subsequent neurotransmitter release are shaped by the basic property of synapse volume. Using a combination of experimental approaches and computational models, we found that large synapses are slow and adapt little during ongoing stimulation, while small synapses are fast and show more profound adaptation. This observation leads to a second key concept: since neurons usually have several presynaptic terminals that may vary in volume, a single neuron can, in principle, forward different synaptic signals to different postsynaptic partners. We provide direct evidence that this is the case for bipolar cells of the fish retina. 041b061a72


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