This review of process analytical chemistry is an update to the previous review on this subject published in 1995(A2). The time period covered for this review includes publications written or published from late 1994 until early 1999, with the addition of a few classic references pointing to background information critical to an understanding of a specific topic area. These older references have been critically included as established fundamental works. New topics covered in this review not previously treated as separate subjects in past reviews include sampling systems, imaging (via optical spectroscopy), and ultrasonic analysis.

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Process Analytical Chemistry

Waveguide antennas for ultrasonic flowmeters are described in which at least one pair of antennas is used to interrogate a flowing fluid. The waveguides are parallel, each pair defining a plane of interrogation which is parallel or nearly parallel to the flow. Some preferred embodiments use elongated waveguides which effectively interrogate the flow simultaneously along a sufficiently large number of parallel paths so that non-axial components of flow tend to be cancelled. Non-axial components are thereby suppressed or eliminated as significant error sources. The large number of effective paths, over a distributed planar area, also contributes to reliable operation even when the fluid is not single phase, especially if interrogating wavelengths are used which are large compared to scatterer dimensions. Several configurations are disclosed wherein the waveguides or their shields may be maintained clean and free of deposits without interrupting their use in the measurement of flow. In some cases a pair of waveguides may be used to measure not only flow velocity but also other fluid parameters of interest such as liquid level, density, impedance or temperature.

Ultrasonic flowmeters using waveguide antennas

Dense zinc aluminate (gahnite) ceramics have been prepared at different sinter temperatures ranging from 1200 to 1600 °C from zinc aluminate powder prepared via the solid-state synthesis. A maximum achieved relative density of 93% was achieved. Several bulk properties like Young's modulus, heat capacity, thermal diffusivity and conductivity have been determined and estimations of the bulk properties at 100% density are made. Furthermore, in spinel-type materials like zinc aluminate the process of cation inversion occurs, which is in general not taken into account in computer simulations for the prediction of bulk properties. In order to determine whether the amount of cation inversion can be influenced by the preparation method resulting in different bulk properties, zinc aluminate powders were synthesised using solid-state synthesis, co-precipitation and a sol-gel method at different temperatures. The resulting powders were zinc deficient due to the volatile nature of zinc at the calcining temperatures. The cation inversion of these powders was investigated using solid-state MAS 27A1 NMR indicating that the cation inversion is very small for pure zinc aluminate irrespective of the preparation method.

Structural, elastic, thermophysical and dielectric properties of zinc aluminate (ZnAl2O4)

A method and apparatus for measuring properties of a liquid composition includes a mechanical resonator, such as a thickness shear mode resonator or a tuning fork resonator, connected to a measurement circuit. The measurement circuit provides a variable frequency input signal to the tuning fork, causing the mechanical resonator to oscillate. To test the properties of a liquid composition, the mechanical resonator is placed inside a sample well containing a small amount of the liquid. The input signal is then sent to the mechanical resonator and swept over a selected frequency range, preferably less than 1 MHz to prevent the liquid being tested from exhibiting gel-like characteristics and causing false readings. The mechanical resonator's response over the frequency range depends on various characteristics of the liquid being tested, such as the temperature, viscosity, and other physical properties. Particular mechanical resonators, such as tuning fork resonators, can also be used to measure a liquid composition's electrical properties, such as the dielectric constant and conductivity, because the tuning fork's structure allows a high degree of electrical coupling between the tuning fork and the surrounding liquid. The mechanical resonator can be covered with a coating to impart additional special detection properties to the resonator, and multiple resonators can be attached together as a single sensor to obtain multiple frequency responses. The invention is particularly suitable for combinatorial chemistry applications, which require rapid analysis of chemical properties for screening.

Method and apparatus for characterizing materials by using a mechanical resonator

fundamentals and applications of ultrasonic waves is available in our digital library an online access to it is set as public so you can download it instantly. Our book servers spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the fundamentals and applications of ultrasonic waves is universally compatible with any devices to read.

Fundamentals And Applications Of Ultrasonic Waves

Devices for covering up the effect of a pockmark in the outer layer of a safety glass windshield or the like include means for evacuating the atmosphere around the pockmark; sealing off the immediate area surrounding the pockmark; applying a highly-penetrating transparent liquid under pressure to the sealed area to force the liquid to penetrate the crevices of the fracture surrounding the pockmark. The transparent liquid fills the microscopic crevices surrounding the pockmark and then is hardened to make the pockmark permanently transparent and effectively invisible as one looks through the safety glass.

Ultrasonic measurements for process control

A guided torsional wave sensor has a cross-section with a strong interaction of torsional wave energy and the surrounding fluid, such that a wave propagates in the sensor with a functional dependence on a single fluid characteristic. In one embodiment, the sensor body is optimized for fluid density. Diamond, polyhedral and curved-sided embodiments are described. In another embodiment, the sensor body responds to fluid viscosity. This embodiment is preferably hollow, and may include threaded, fractal or roughened surface features to enhance viscous coupling. Different systems include further sensors, sensors with portions of differing profile, and special mounting or activation structures.

Torsional wave fluid sensor and system

An ultrasonic densitometer for measuring the density or a density related parameter of a fluid has at least one transducer assembly that transmits and receives torsional waves guided in an axially extending sensor that is at least partially immersed in the fluid. The sensor has a noncircular cross section, typically rectangular, with dimensions, aspect ratio, frequency and bandwidth selected to limit dispersion. This non-circularity creates an inverse and substantially linear relation between the density of the fluid and the velocity of the torsional wave in the sensor. To meet special requirements, the sensor can take a variety of forms including axially curved, axially profiled, segmented or longitudinally composite. This densitometer, alone or in combination with conventional auxiliary ultrasonic measuring systems, can measure fluid density, density profiles, liquid level, viscosity, mass flow rate, gas pressure, and boiling or condensation, including measurements of flowing fluids in small conduits.

Slow torsional wave densitometer

Slow Torsional Wave Sensors

The invention discloses an ultrasonic mass flowmeter. The ultrasonic mass flowmeter comprises a liquid flowing pipe, at least one group of ultrasonic sensors arranged on the pipe, and a measurement host, wherein the measurement host controls the ultrasonic sensors to transmit and receive signals to obtain mass and flow values; the ultrasonic sensors are composed of ultrasonic transmitters and ultrasonic receivers, which are on the upper side and the lower side of the pipe respectively and located inside a plane passing through the axis of the pipe. According to the ultrasonic mass flowmeter, with the high-frequency characteristics, ultrasonic waves can complete high-precision measurement and are high in mass and flow measurement precision. The ultrasonic mass flowmeter is simple in device structure, namely, is composed of the sensors and the host without complicated mechanical parts. Meanwhile, the ultrasonic mass flowmeter is applicable to mass and flow measurement of various kinds of fluid, thereby being diversified in measured objects. Also, the ultrasonic mass flowmeter can achieve comprehensive analysis of various parameters of fluid to be measurement and can measure the information of mass, flow, density, temperature, energy and the like simultaneously.

Lawrence C. Lynnworth

Papers

Ultrasonic measurements for process control

Torsional wave fluid sensor and system

Slow torsional wave densitometer

Slow Torsional Wave Sensors

Ultrasonic Mass Flowmeter