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Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Society of Automotive Engineers standard SAE J1708 is a standard used for serial communications between ECUs on a heavy duty vehicle and also between a computer and the vehicle. With respect to Open System Interconnection model (OSI), J1708 defines the physical layer. Common higher layer protocols that operate on top of J1708 are SAE J1587 and SAE J1922. The protocol is maintained by SAE International.
The standard defines a 2-wire 18 gauge wire cable that can run up to 130 feet (40 m) and operates at 9600 bit/s. A message is composed of up to 21 characters, unless the engine is stopped and the vehicle is not moving in which case transmitters are allowed to exceed the 21 byte max message length. Messages start with a Message ID (MID) character and finish with a checksum at the end. Characters are transmitted in the common 8N1 format.
The hardware utilized are RS-485 transceivers wired for open collector operation through the use of a pullup and pulldown of the separate data lines. Transmission is accomplished by controlling the driver enable pin of the transceiver. This method allows multiple devices to share the bus without the need for a single master node. Collisions are avoided by monitoring the bus while transmitting the MID to ensure that another node has not simultaneously transmitted a MID with a higher priority.
SAE J1708, although still widely used, is replaced by SAE J1939 which is a CAN protocol.
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Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Society of Automotive Engineers standard SAE J1708 is a standard used for serial communications between ECUs on a heavy duty vehicle and also between a computer and the vehicle. With respect to Open System Interconnection model (OSI), J1708 defines the physical layer. Common higher layer protocols that operate on top of J1708 are SAE J1587 and SAE J1922. The protocol is maintained by SAE International.
Society of Automotive Engineers standard SAE J1587 is an automotive diagnostic protocol standard developed by the Society of Automotive Engineers (SAE) for heavy-duty and most medium-duty vehicles built after 1985. The J1587 protocol uses different diagnostic connectors. Up to 1995, individual OEMs used their own connectors. From 1996 to 2001, the 6-pin Deutsch-connector was standard. Beginning in 2001, most OEMs converted to the 9-pin Deutsch. Some OEMs still use the 6-pin Deutsch. It has mostly been used for US made vehicles, and also by Volvo. Other European brands have usually used KWP. The pinout for the 9-pin connector is: The pinout for the 6-pin connector is: SAE J1708 makes up the physical and data link layers while SAE J1587 makes up the transport and application layers with respect to the OSI model. SAE J1587 is used in conjunction with SAE J1708 for automobile communication.
Vector Informatik develops software tools and components for networking of electronic systems based on the serial bus systems CAN, LIN, FlexRay, MOST, Ethernet, AFDX, ARINC 429, and SAE J1708 as well as on CAN-based protocols such as SAE J1939, SAE J1587, ISO 11783, NMEA 2000, ARINC, CANaerospace, CANopen and more. The headquarters of the company Vector Informatik GmbH is in Stuttgart, Germany. Subsidiaries include Braunschweig, Munich, Hamburg, Regensburg along with international subsidiaries in Brazil, China, France, Italy, England, India, Japan, South Korea, Austria, Sweden, and the USA. Vector Informatik also includes Vector Consulting Services GmbH, a consultation firm specializing in optimization of technical product development. Altogether, these companies are referred to as the Vector Group.
SAE J2452 is a standard defined by the Society of Automotive Engineers to measure the rolling resistance of tires. Where the older standard, SAE J1269, produces measurements of rolling resistance under steady-state (i.e. thermally equilibrated) operating conditions, SAE J2452 produces measurements during a transient history of speed that is intended to mimic a vehicle coastdown event. During the SAE J2452 test, the tire is not in thermal equilibrium, but the coastdown event is rapid enough that the tire operates at a roughly iso-thermal condition. Either procedure may be used to investigate the effects of different vehicle loads (weight), tire pressures and vehicle speeds. The rolling resistance coefficient (RRC) indicates the amount of force required to overcome the hysteresis of the material as the tire rolls. Tire pressure, vehicle weight and velocity all play a role in how much force is lost to rolling resistance. The basic model equation for SAE J2452 is: Rolling Resistance (N / Lbs) = Pα Zβ (a + bV + cV2) where: P is the tire inflation pressure (kPa / psi) Z is the applied load for vehicle weight (N / Lbs) V is the vehicle speed (km/h / mph) alpha, beta, a, b, c are the coefficients for the model. The units of the coefficients are matched to the units used in the model (i.e. metric/Imperial).
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Joe Louis.