Miniature Probe Research Articles

Simple technique for frequency-response enhancement of miniature pressure probes

Simple technique for frequency-response enhancement of miniature pressure probes

Technical Note Parasitic thermovoltage in the multithermocouple probe, its explanation and elimination

The parasitic thermovoltage can influence the temperature measurement during hyperthermia using the miniature multithermocouple probes with a common wire. It was noticed that, when a thermocouple junction is placed in a sharp thermal gradient, a parasitic thermovoltage is added to the voltage of all remaining thermocouples situated in the direction to the tip of the probe. This article gives the theoretical explanation, experimental verification, and practical elimination of this phenomenon.

MIXED-CONVECTION HEAT TRANSFER TO SODIUM IN A VERTICAL PIPE

Experimental turbulent mixed-convection data are presented for sodium in a uniformly heated vertical pipe. The behavior is found to be opposite to that established for fluids of higher Prandtl number, including mercury, with heat transfer enhanced in upward flow and impaired in downward flow. Velocity and temperature profiles in the sodium have been measured using miniature magnet probes. Velocity profiles are similar to those observed under comparable conditions in other fluids; temperature profiles are somewhat different, with significant variation of temperature extending almost to the pipe centerline. Experimental measurements are compared with predictions obtained using a low-Reynolds-number κ-ε turbulence model. Reasonable agreement is achieved for upward flow, but the model overpredicts heal transfer rates for downward flow, as in the case of conventional fluids.

Miniature multihole pressure probes and their neural-network-based calibration

Miniature multihole pressure probes and their neural-network-based calibration

Clinicopathological evaluation of intralaryngeal ultrasonography

We used a miniature ultrasonic probe to study its diagnostic application in the detection of laryngeal lesions. Using the immersion method and an extracted human larynx, we evaluated ultrasonic images, identified the layered structure of vocal folds, and examined clinical cases following the study of diagnostic application. By the immersion method, ultrasonic images revealed that the membranous vocal fold was separated into three layers. We identified the histological structures of these three layers by comparing the ultrasonic images with the corresponding histologies. The first layer (hyperechoic) was the epithelial and the superficial layer of the lamina propria; the second layer (hypoechoic) was the vocal ligament; and the third layer (hyperechoic) was the deep layer of the lamina propria. On the basis of this study, we then evaluated ultrasonographic images of clinical cases. Benign lesions such as vocal nodules or vocal polyps were noted on the layered structure of the mucosa, especially, polyps as hyperechoic images. Furthermore, glottic cancer lesions demonstrated hypoechoic images and sometimes revealed destruction of the layered structures. These results suggest that intralaryngeal ultrasonography can be useful as a clinical application for the detection of tumor involvement in the vocal folds.

Current distributions in multifilamentary conductors: the influence of intergrowths

The modelling of both critical and remanent states (i.e., the current density and field distributions) in periodic arrays of flat superconducting strips is important for calculating the AC losses in multifilamentary tapes made for power applications. We model the current and field profiles for such magnetically coupled conductors, and have measured these dependences for BSCCO-22223 tapes using a miniature scanning Hall probe technique. The results indicate that the filaments are also electrically connected to a significant extent, which must be caused by superconducting intergrowths between individual filaments.

A miniature probe enables clear demonstration of the cystic duct during laparoscopic cholecystectomy.

We performed intraoperative ultrasonography with a miniature probe to explore the biliary anatomy, especially the cystic duct, during laparoscopic cholecystectomy. By using this radial-type probe introduced into a hard metal sheath with a balloon at the end, the plane containing Calot's triangle can be scanned easily when the gallbladder is extracted to the right side, thereby facilitating the identification of the cystic duct as well as the common ducts. In 30 cases, no common duct stone was found and the cystic duct was clearly identified. This radial-type miniature probe can be used to locate the cystic duct and avoid inadvertant incision or division of the common ducts.

Simultaneous measurements of bulk and shear moduli of voided polymers in the 0.5- to 2.5-kHz range

The complex, frequency-dependent, bulk and shear moduli of polymers containing microscopic inclusions can be measured simultaneously [see J. Acoust. Soc. Am. 102, 3549–3555 (1997)]. The method consists in measuring the surface dynamics of the sample under harmonic test by noncontact laser Doppler interferometry and by matching the experimental results with numerical predictions in which the two complex moduli are the adjustable parameters. Results obtained with a sample of known properties (lucite) confirm the validity of the method. Improvements to the system will be discussed. It is more compact and it uses only two miniature fiberoptic probe heads which can be scanned along the surface of the sample. Automated data acquisition with a lock-in amplifier greatly improves the speed of the experiment and enables good frequency resolution (less than 1 Hz) between 0.5 and 2.5 kHz. The measurement errors associated with this technique will be discussed in detail. In particular, measurements made on several samples taken from the same panel will be presented to quantify manufacturing variability. [Work supported by ONR, code 334.]

The influence of subsurface moisture on rill system evolution

Rill development studies have focused almost exclusively on surface erosion processes and critical threshold hydraulic conditions. Characteristic rill features, such as arcuate headcuts and knickpoints, are morphologically similar to the ‘theatre-headed’ valleys which have been associated with ‘sapping’ processes at various scales. This paper reports on laboratory experiments designed to identify linkages between surface flow hydraulics, subsurface moisture conditions and rill development. Experiments were carried out in a 16·57 m2 flume under simulated rainfall with soil samples up to 0·15 m depth in which moisture conditions were monitored by miniature time-domain reflectometer probes. Tests showed complex responses in which some rill incision reflected surface flow conditions, but major rill system development with markedly enhanced sediment yield was closely associated with high soil moisture contents. It was not possible to measure seepage forces directly, but calculation and observation indicate that these were less important than reduction in soil strength with saturation, which resulted in increased effective runoff erosivity. This caused concentrated undercutting along the water table at rill walls, while slightly stronger surface layers above the water table formed microscarps. These retreated along the water table into interrill surfaces, producing residual pediment transport slopes. The microscarps eventually disappeared when the water table reached the surface, eliminating differential soil strength. The experiments showed complex relationships between surface and subsurface erosional processes in evolving rill systems, strongly influenced by soil moisture dynamics. The very small topographic and hydraulic head amplitudes indicate that seepage forces and ‘sapping’ were minimal. The dominant effect of soil moisture was reduction of soil strength with saturation, and increased runoff entrainment. Experimental conditions were not unusual, either for agricultural fields or natural hillslopes, and the intricate interrelationship of surface and subsurface erosion processes observed is probably not uncommon. Attempts to link specific morphologic features at rill scale to dominance of surface or subsurface processes alone are therefore unlikely to be successful or reliable. © 1998 John Wiley & Sons, Ltd.

The influence of subsurface moisture on rill system evolution

Rill development studies have focused almost exclusively on surface erosion processes and critical threshold hydraulic conditions. Characteristic rill features, such as arcuate headcuts and knickpoints, are morphologically similar to the ‘theatre-headed’ valleys which have been associated with ‘sapping’ processes at various scales. This paper reports on laboratory experiments designed to identify linkages between surface flow hydraulics, subsurface moisture conditions and rill development. Experiments were carried out in a 16·57 m2 flume under simulated rainfall with soil samples up to 0·15 m depth in which moisture conditions were monitored by miniature time-domain reflectometer probes. Tests showed complex responses in which some rill incision reflected surface flow conditions, but major rill system development with markedly enhanced sediment yield was closely associated with high soil moisture contents. It was not possible to measure seepage forces directly, but calculation and observation indicate that these were less important than reduction in soil strength with saturation, which resulted in increased effective runoff erosivity. This caused concentrated undercutting along the water table at rill walls, while slightly stronger surface layers above the water table formed microscarps. These retreated along the water table into interrill surfaces, producing residual pediment transport slopes. The microscarps eventually disappeared when the water table reached the surface, eliminating differential soil strength. The experiments showed complex relationships between surface and subsurface erosional processes in evolving rill systems, strongly influenced by soil moisture dynamics. The very small topographic and hydraulic head amplitudes indicate that seepage forces and ‘sapping’ were minimal. The dominant effect of soil moisture was reduction of soil strength with saturation, and increased runoff entrainment. Experimental conditions were not unusual, either for agricultural fields or natural hillslopes, and the intricate interrelationship of surface and subsurface erosion processes observed is probably not uncommon. Attempts to link specific morphologic features at rill scale to dominance of surface or subsurface processes alone are therefore unlikely to be successful or reliable. © 1998 John Wiley & Sons, Ltd.

Experimental investigation of a confined heated sodium jet in a co-flow

Low-Prandtl-number convection is investigated in vertical axisymmetric turbulent buoyant sodium jets discharging into a slowly moving ambient. Measurements of mean velocity, mean temperature and temperature fluctuations are performed simultaneously using a miniature permanent-magnet flowmeter probe. By varying the ratio of momentum to buoyancy flux, or the densimetric Froude number, different intensities of buoyancy are obtained giving a range of conditions encompassing forced-convection jets, buoyant jets and plumes. In line with the classical properties of jets the radial velocity and temperature profiles can be described by the Gaussian function, independent of the flow regime, at all axial measuring positions. The axial decay of the centreline mean velocity for sodium is the same as for fluids of higher Prandtl number, governed by power laws with indices of −1 for forced convection, −2/3 for the transitional buoyant region and −1/3 for plume flow. In contrast, the centreline mean temperatures for sodium plumes decrease with a power of −1 compared with the −5/3 decay for fluids of higher Prandtl number. The different behaviour in sodium is due to the dominance of molecular diffusion in heat transport, while momentum transport is dictated by turbulent diffusion, which gives a similarity solution for forced-convection jets but not for buoyant jets or plumes. The radial profiles of the temperature r.m.s. values can be described by an axisymmetric curve with two maxima, independent of the flow regime, at all axial measuring positions and the two maxima are more pronounced than in conventional fluids. The temperature fluctuations are analysed to give statistical parameters such as minimum and maximum values, skewness, flatness, probability density functions and spectral distribution. The spectral distributions display both a convective subrange and the conductive subrange predicted for fluids of low Prandtl number. Integral length scales of the temperature fluctuations are evaluated and found to be significantly smaller than turbulent velocity scales.

Miniature electric near-field probes for measuring 3-D fields in planar microwave circuits

Three-dimensional (3-D) electric near-field probes applicable to the 0.05-20-GHz band have been developed, which can measure both the magnitude and the phase of the microwave field inside radio-frequency (RF) and microwave circuits. The field probes have very small dimensions and do not need to be connected to the operating device-under-test (DUT), therefore, the circuit properties are nearly not disturbed by the probe, Investigations on different circuits (e.g., antenna, meander lines, filters, and power amplifiers) show that such near-field probes can be applied not only to simple passive circuits, but also to measure the fields inside complex active circuits. These simple, stable, and cheap field probes are very useful for assisting the design of microwave circuits, antenna diagnostics, and testing products in industry.

A four-sensor hot-wire probe system for three-component velocity measurement

A velocity measurement system based on a miniature four-sensor hot-wire probe capable of simultaneous three-component measurements throughout a wide range of flow angles has been developed. The calibration technique allows measurements to be made throughout the acceptance cone of the probe without being restricted by the errors associated with analytic angle response equations. This technique is based upon look-up tables with values which tend to vary slowly, allowing a simple interpolation scheme to be used. Measurements made in a turbulent pipe flow verify the accuracy of the technique.

A miniature triple hot-wire probe for wall bounded flows

Four orthogonal and one non-orthogonal miniature triple hot-wire probes have been developed and tested in a two-dimensional turbulent boundary layer. The influence of the different wire configurations on measurements of the Reynolds stresses has been studied. A directional calibration with an analytical solution for the wire response equations was used for the measurements of the non-orthogonal probe and was tested for the orthogonal probes in order to correct their possible geometrical imperfections. It is shown that a directional calibration does not significantly improve the quality of the measurements for precisely manufactured orthogonal probes and that measuring errors are related rather to the measuring volume, the size of the domain of unique solutions for the instantaneous velocity vector and interference effects, i.e. the wire configuration itself.

The Effect of an Implantable Doppler Probe on the Salvage of Microvascular Tissue Transplants

One hundred forty-seven flaps in 135 consecutive patients undergoing microvascular transplantation were monitored using a miniature Doppler ultrasonic probe. Using a modification of a technique described previously by Swartz, the probes were secured to the outflow vein of the flap with Vicryl mesh. Twenty instances of thrombosis or spasm were detected in 16 patients, and all flaps were salvaged (100 percent). There were four false positive and no false negative results. This probe allows for safe, continuous monitoring of flap blood flow, which permits the rapid detection and hence rapid treatment of postoperative complications. Our experience suggests that a significant improvement in the salvage rate of microvascular transplants may be attainable with the use of this device.

Endosonographic diagnosis of submucosal upper gastrointestinal tract lesions and giant fold gastropathies by miniature ultrasound probe. A prospective study

Endosonographic diagnosis of submucosal upper gastrointestinal tract lesions and giant fold gastropathies by miniature ultrasound probe. A prospective study

A miniature monoblock backward phase-Doppler unit

The phase-Doppler technique, allowing one to measure velocities and sizes of individual spherical particles in moving flows, is a very popular technique. Nevertheless, the bulkiness of the device and the need for accurate adjustments still impose restrictions in use in a large number of industrial situations. We present here a miniature phase-Doppler probe in which the emitting and collecting units are assembled in a compact way. The performance of the device is numerically and experimentally demonstrated.

Ultrasonic Tactile Sensor: An Experimental Study to Evaluate the Depth of Invasion in Esophageal Squamous Cell Carcinomas

Abstract: To date, an objective scale for evaluation of tissue stiffness has been lacking. A new instrument, the “ultrasonic tactile sensor (UTS)”, allows objective evaluation of stiffness. For the purpose of evaluating cancer stiffness, we first introduce an experimental study on tissue stiffness using surgically resected specimens of esophageal squamous cell carcinomas with no special preoperative treatment. From November 1995 to January 1996, the authors examined 11 esophageal cancer specimens. Although this experiment revealed no differences between normal mucosa and mucosal cancer in the esophagus, significant differences between mucosal and submucosal cancers in terms of tissue stiffness were clearly demonstrated. Therefore, UTS examination is useful for assessing malignant invasion, thereby providing valuable information for determining appropriate indications for endoscopic mucosal resection. We currently perform this UTS examination using a miniature probe during preoperative endoscopy. We anticipate that this new method will become an essential tool for evaluating the depth of invasion in esophageal cancer preoperatively.

RF measurement technique for characterizing thin dielectric films

We have developed a novel technique for measuring the dielectric constant and loss tangent of a thin film dielectric material up to 5 GHz. The dielectric film needs to be deposited on a metal layer and capped with a metal electrode layer. The bottom metal layer does not have to be very conductive, as long as its sheet resistance is uniform and known. Only one step lithography on the top metal layer is required. No dc electrical contact to the bottom metal layer is necessary. The measurement is taken with a Vector Network Analyzer and a coplanar-wave-guide miniature wafer probe.

Dieulafoy's Vascular Malformation: Role of Endoscopic Ultrasonography in Therapeutic Decision-Making

Background: Dieulafoy's vascular malformation may cause severe, potentially life-threatening gastro-intestinal bleeding. Endoscopic diagnosis may be difficult because of minute mucosal lesions, and additional intramural abnormalities are usually not encountered. Endoluminal high-frequency ultrasonography is a new modality for imaging intramural and perivisceral structures. Methods: We report two cases of recurrent severe gastric bleeding in which different endosonographic modalities were used in the diagnosis of Dieulafoy's malformation, and the impact of endosonography on therapeutic strategy is discussed. In the first case a radial-scanning 7.5/12-MHz echoendoscope and a linear 20-MHz miniature probe were applied for B-mode imaging in a stable-state patient who had undergone previous endoscopic sclerotherapy, and arterial flow signals from the small intramural lesion were recorded using a 10-MHz transendoscopic pulsed Doppler probe. In the other case urgent endosonography was performed shortly after a bleeding episode, disclosing an aberrant large-calibre artery entering the gastric wall with a long submucosal branch. Results: Both patients were successfully operated on with a transabdominal approach. Conclusion: Endosonography is a quick and safe diagnostic method and should be considered when vascular malformations are suspected as the cause of gastric bleeding.