A J-aerial is a dipole type aerial consisting of a three-quarter wavelength vertical portion and a quarter-wavelength portion parallel to it, the feeding points being equidistant from the junction. Research J-aerial
A jack plane is a carpenters, long, heavy plane used for smoothing large areas of rough wood, and for rough shaving of wood, such as sticking doors. Research Jack Plane
A Jack saw or panel saw is a light hand saw with a narrow, usually slightly tapering, blade of fine teeth, for cutting timber thinly. Research Jack Saw
The Jansky is the unit of radiation received from outer space, used in radio astronomy. It is equal to 10-26 watts per square metre per hertz, and is named after the USA engineer Karl Jansky. Research Jansky
JavaScript is an interpreted computer language supported by some client Web browsers. It was first introduced by Netscape in their Navigator Web browser. It allows embed commands in an HTML page which are loaded by the client Web browser as a part of the HTML document. These commands can be triggered when the user clicks on page items, manipulates gadgets and fields in an HTML form, or moves through the page history list. Research JavaScript
Javelin Plus is a financial modelling tool designed for the development and analysis of business planning models. Because Javelin Plus is faster and, in many ways, easier to use than a spreadsheet, it appeals to a broad base of business analysts and financial planning professionals. Javelin Plus' s understanding of time periods such as weeks, months, quarters, and years makes it helpful in creating time-series models. It automatically calculates monthly figures from input data.
Javelin Plus minimises errors that are difficult to spot in complicated financial models by using formula-name references rather than cell references. Javelin Plus allows you to construct a model by defining relationships rather than by tediously defining a series of cells. Data is stored in an information base instead of a spreadsheet, so you can create the relationships between the different values and show them in several views rather than in a simple, flat matrix (although that is one of the options). Javelin Plus makes it easy to do forecasting because you can actually draw a graph in the quick graph view, and the product will insert the respective numbers into that variable' s data table (another view). For example, if you create a variable called East which is equal to the total sales of Boston, New York, and Toronto and a variable called First Quarter equal to January, February, and March, when you call for East and First Quarter,
Javelin Plus automatically adds the data associated with the three cities for the first three months. One of the most interesting aspects of Javelin Plus is the snap-in building block capability which allows users to develop fully integrated add-in tools. Snap-ins are open-architecture design features, similar to templates, that allow you to create unlimited applications which can be accessed as needed.
Javelin Plus allows text and date variables to be used in modelling as if they were numeric variables. This means you can base calculations in models on non-numeric data. You can perform true date arithmetic which is especially useful for querying in models that include databases. Database functions such as sorting and cross-tabulation are included. Javelin Plus also has improved worksheet-printing options for the worksheet view, including user-specified page breaks, margins, setup strings, and printer fonts. Graph styles include high-low-close, mixed line/bar, and XY plots of up to seven variables. Research Javelin Plus
JBMail is a unique POP3 mail reader for the Windows operating system which gives the user direct access to his or her mailbox. You can view, preview, delete, save, print, retrieve attachments, or delete junk mail. JBMail gives you fast access to your mail, because it lets you manipulate e-mails without having to first download them. With its junk mail filtering, it's an excellent way to kill large amounts of spam. 'Purge' and 'partial' access modes let you get into very full mailboxes.
JBMail is useful for anybody who gets lots of mail, and even useful for technical support people trying to fix mailboxes. Research JBMail
A jet engine is a form of gas-turbine engine used in aircraft, in which the thrust is generated by a jet of exhaust gas discharged from a nozzle at the rear of the engine.
Jet engines were developed concurrently in the UK and in Germany. Whittle's centrifugal flow turbojet was patented in 1930 and first tested later in the same year. The first jet aeroplane to fly was the German Heinkel He 178 in 1939, powered by an engine designed by von Ohain. In a turbojet, air is taken into the engine and compressed, then mixed with fuel and burnt. The combustion gases then pass through a turbine, the power from which drives the compressor, after which the remaining energy in the gas is converted to kinetic energy in the exhaust cone and propelling nozzle, and ejected as a high- velocity jet. The configuration of the propelling nozzle is critical for maximum efficiency at a given speed. Turbojets are most efficient at high speeds: for speeds below 800 km/h a more efficient type of engine is the turboprop. This works on the same principle as the turbojet, but most of the energy of the combustion gases drives the turbine, which is used to power a propeller as well as the compressor. A small amount of forward thrust is also obtained from the
exhaust gases. A major use of turboprop engines is in helicopters. In the bypass jet engine two air compressors, one low- pressure and one high-pressure, are used. After passage through the first, low-pressure compressor, part of the air intake bypasses the combustion chamber and turbine. The combination of this cold air jet and the hot exhaust jet gives a much larger mass of air and therefore increased thrust, without an increase in fuel consumption. This principle is taken even further in the turbofan engine, which incorporates a large fan to accelerate still more air outside the engine proper, as well as using the bypass principle. Current research priorities include the reduction of polluting emissions from jet engines, and the development of ceramic engine components, which are lighter and can work at higher temperatures than metals. Research Jet Engine
In electronics, Johnson Noise is unwanted voltage variations which manifest in a receiver as noise and in other types of apparatus as spurious signals in the output. Johnson Noise is due to the random motion of electrons in a conductor, which increases with temperature. Research Johnson Noise
Joly's steam calorimeter is an apparatus invented by John Joly to measure the specific heat capacity of a gas at a constant volume. Two equal spherical containers are suspended from the opposite ends of a balancearm. One sphere is evacuated and the other contains the sample gas. The whole apparatus is enclosed in a steambath, the specific heat capacity of the sample gas being calculated from the difference between the masses of the water that condenses on each sphere. Research Joly's Steam Calorimeter
JotALot is a lean and mean notebook program for the PC designed for addresses, recipes, weblinks, loose ideas and the other little things that users need to jot down quickly and retrieve even quicker. With JotALot's lightning fast free text search all you have to do is type the first few letters of a name, street address or email and JotALot will find the information you need almost instantly. The link facility lets you link your entries to web pages, e-mail addresses, files and programs. The built-in synchronization makes it easy to keep your address book at work up to date with your address book at home. JotALot starts almost instantly and uses very little memory. Research JotALot
The Joule-Thomson effect (also known as the Joule-Kelvin effect) is the change in temperature that occurs when a gas expands through a porous plug into a region of lower pressure. For most real gases the temperature falls under these circumstances as the gas has to do internal work in overcoming the intermolecular forces to enable the expansion to take place. This is a deviation from Joule's law. There is usually also a deviation from Boyle's law, which can cause either a rise or a fall in temperature since any increase in the product of pressure and volume is a measure of external work done. At a given pressure, there is a particular temperature, called the inversion temperature of the gas, at which the rise in temperature from the Boyle's law deviation is balanced by the fall from the Joule's law deviation. There is then no temperature change. Above the inversion temperature the gas is heated by expansion, below it, it is cooled. The effect was discovered by James Joule working in collaboration with WilliamThomson (who
later became LordKelvin). Research Joule-Thomson Effect
Jpeg is a compressed bitmap image format intended for the digital storage of photographic images. Jpeg was developed by an organisation called the Joint Photographic Experts Group, comprising cooperation between the ISO and the CCITT. Jpeg features variable compression from very high, with a corresponding high loss of picture clarity, through to very low with very little loss of picture quality. Early complaints about Jpeg were that it's compression and decompression routines were slow, but these complaints have been annulled with the advent of faster computers. Research Jpeg
The JRC NRD-515 is a classicJapanese made general coverage receiver manufactured between 1979 and 1986 and providing coverage from 100 kHz to 34 Mhz in AM, SSB, CW and RTTY modes. The receiver was rated among the top performers of its time. Research JRC NRD-515
JS Office is an integrated suite of applications for the PC that uses powerful database technology to provide easy access to a number of useful programs. The program integrates word processing, contact organization, appointment and task scheduling, fax capabilities, an email client, and a file compression system. It also will perform calculations of loan payments and amortization schedules, as well as conversions between metric and non-metric units. JS Office can be installed in English, French, German, Italian, Spanish, Dutch, or Norwegian. Research JS Office
A junction detector is a sensitive detector of ionizing radiation in which the output is a current pulse proportional to the energy falling in or near the depletion region of a reverse-biased semiconductor junction. The first types were made by evaporating a thin layer of gold on to a polished wafer of n-type germanium; however, gold-silicon devices can be operated at room temperature and these have superseded the germanium type, which have to be operated at the temperature of liquid nitrogen to reduce noise. When the gold-silicon junction is reverse-biased a depletion region, devoid of charge carriers, forms in the silicon. Incoming ionizing radiation falling in this depletion region creates pairs of electrons and holes, which both have to be collected in order to give an output pulse proportional to the energy of the detected particle.
Junction detectors are used in medicine and biology as well as in space systems. Research Junction Detector
Just The Fax is a personal faxcomputer program for the PC that creates, sends, and receives faxes. Create faxes and cover sheets using a WYSIWYG editor. You can have incoming faxes announced by customizing the program with an optional sound file. Put together a library of cover sheet templates easily, and maintain a phone number database for frequently used numbers. With this version, you can use the latest fax technology, including fax-modem auto detection. Research Just The Fax
Jute is a fibre obtained from the inner bark of certain plants and used for making a coarse fabric which is used for making sacks and as a wall hanging. Research Jute
Juvenile hormone is secreted by some insects from a pair of endocrine glands (the corpora allata) close to the brain. It inhibits metamorphosis and maintains the presence of larval features. Research Juvenile Hormone
Abbreviations
SciTech
Research J-aerial
