Echo Height Research Articles

The Effects of Paint Film Thickness on the Reflection Echo Height of Ultrasonic Testing

The Effects of Paint Film Thickness on the Reflection Echo Height of Ultrasonic Testing

A 35-GHz polarimetrie Doppler radar and its application for observing clouds associated with Typhoon Nuri

Millimeter-wavelength radar has proved to be an effective instrument for cloud observation and research. In this study, 8-mm-wavelength cloud radar (MMCR) with Doppler and polarization capabilities was used to investigate cloud dynamics in China for the first time. Its design, system specifications, calibration, and application in measuring clouds associated with typhoon are discussed in this article. The cloud radar measurements of radar reflectivity (Z), Doppler velocity (Vr), velocity spectrum width (Sw) and the depolarization ratio (LDR) at vertical incidence were used to analyze the microphysical and dynamic processes of the cloud system and precipitation associated with Typhoon Nuri, which occurred in southern China in August 2008. The results show the reflectivity observed using MMCR to be consistent with the echo height and the melting-layer location data obtained by the nearby China S-band new-generation weather radar (SA), but the Ka-band MMCR provided more detailed structural information about clouds and weak precipitation data than did the SA radar. The variation of radar reflectivity and LDR in vertical structure reveals the transformation of particle phase from ice to water. The vertical velocity and velocity spectrum width of MMCR observations indicate an updraft and strong turbulence in the stratiform cloud layer. MMCR provides a valuable new technology for meteorological research in China.

Investigation on lubrication condition of piston pin in real engine block with ultrasonic technique

In situ observations of variations in the lubrication conditions between a piston pin and a pin boss in a real automotive engine block operating under low rotational speeds, such as during activation of the engine, were carried out by measuring the echo height detected by an ultrasonic probe installed into the cylindrical piston pin. It was possible to estimate the oil film thickness directly within an accuracy of 1 µm by the echo height ratio reflected from the piston pin surface. The amplitude of the reflected wave (echo height) under the condition including an air bubble was higher than that without an air bubble, and the phase of the wave approached that of the dry condition. It thus became possible to detect cavitation between the piston pin and the pin boss. In particular, cavitations were continuously observed at the anti-thrust side in the upstroke under 300 rpm operation. However, it was at least clarified that the lubrication condition in the thrust side of the piston pin supporting a load under a stable condition was sufficient to maintain safe operation, since a continuous oil film without a cavity was formed at the thrust side even for a low rotational speed. Copyright © 2011 John Wiley & Sons, Ltd.

Comparing individual tree detection and the area-based statistical approach for the retrieval of forest stand characteristics using airborne laser scanning in Scots pine stands

Airborne laser scanning based forest inventories employ two major methods: individual tree detection (ITD) and the area-based statistical approach (ABSA). ITD is based on the assumption that trees are of a certain form and can be delineated using airborne laser scanning techniques, whereas ABSA is an empirical method based on the relations between area-level forest attributes and laser echo height distributions. These two methods are compared here within the same test area in terms of their usefulness for estimating mean forest stand characteristics and tree size distributions. All evaluations were performed using leave-one-out cross validation. The average errors in volume and basal area did not differ significantly between the methods. ABSA resulted in overall better accuracies when estimating the diameter and height of the basal area median tree and the number of stems, whereas ITD produced significantly biased estimates for the number of stems and the mean tree size. Tree size distributions were estimated with slightly better accuracy using ABSA. More comprehensive investigations revealed that both methods were not able to estimate forest structure (tree size distribution and spatial distribution of tree locations), which in turn, affected the estimation accuracies.

Airborne Laser Scanning for the Site Type Identification of Mature Boreal Forest Stands

In Finland, forest site types are used to assess the need of silvicultural operations and the growth potential of the forests and, therefore, provide important inventory information. This study introduces airborne laser scanner (ALS) data and the k-NN classifier data analysis technique applicable to the site quality assessment of mature forests. Both the echo height and the intensity value percentiles of different echo types of ALS data were used in the analysis. The data are of 274 mature forest stands of different sizes, belonging to five forest site types, varying from very fertile to poor forests, in Koli National Park, eastern Finland. The k-NN classifier was applied with values of k varying from 1 to 5. The best overall classification accuracy achieved for all the forest site types and for a single type, were 58% and 73%, respectively. The conclusion is that when conducting large-scale forest inventories ALS-data based analysis would be a useful technology for the identification of mature boreal site types. However, the technique could still be improved and further studies are needed to ensure its applicability under different local conditions and with data representing earlier stages of stand development.

Effects of different sensors and leaf-on and leaf-off canopy conditions on echo distributions and individual tree properties derived from airborne laser scanning

The objectives of this study were to quantify and analyze differences in laser height and laser intensity distributions of individual trees obtained from airborne laser scanner (ALS) data for different canopy conditions (leaf-on vs. leaf-off) and sensors. It was also assessed how estimated tree height, stem diameter, and tree species were influenced by these differences. The study was based on 412 trees from a boreal forest reserve in Norway. Three different ALS acquisitions were carried out. Leaf-on and leaf-off data were acquired with the Optech ALTM 3100 sensor, and an additional leaf-on dataset was acquired using the Optech ALTM 1233 sensor. Laser echoes located within the vertical projection of the tree crowns were attributed to different echo categories (“first echoes of many”, “single echoes”, “last echoes of many”) and analyzed. The most pronounced changes in laser height distribution from leaf-on to leaf-off were found for the echo categories denoted as “single” and “last echoes of many” where the distributions were shifted towards the ground under leaf-off conditions. The most pronounced change in the intensity distribution was found for “first echoes of many” where the distribution was extremely skewed towards the lower values under leaf-off conditions compared to leaf-on. Furthermore, the echo height and intensity distributions obtained for the two different sensors also differed significantly. Individual tree properties were estimated fairly accurately in all acquisitions with RMSE ranging from 0.76 to 0.84 m for tree height and from 3.10 to 3.17 cm for stem diameter. It was revealed that tree species was an important model term in both and tree height and stem diameter models. A significantly higher overall accuracy of tree species classification was obtained using the leaf-off acquisition (90 vs. 98%) whereas classification accuracy did not differ much between sensors (90 vs. 93%).

111 超音波法による転がり軸受の潤滑診断の可能性(セッション3 状態監視(2))

Evaluation of a lubrication condition of ball bearing becomes an important issue for safe operation of a machine. In this paper, an application of ultrasonic technique is attempted for a purpose of evaluating the lubrication conditions. Quantitative measurement of a dent size which forms the origin of flaking is important for an evaluation of lubrication conditions. The width of indentation having 0.45mm on a raceway surface of an inner ring becomes possible with the observation of the change in echo height reflected from a boundary surface between housing and outer ring of the ball bearing. Furthermore, it can be possible to evaluate an insufficiency of oil in ball bearing by the observation of reflection echo height variation from a contact surface of outer ring and ball. When a sufficiently oil is supplied to the inlet of contact surface between them, the echo height increases locally. However, degree of its increase becomes lower when oil supply is insufficient, and does not appear at all with running out of oil. A time lag between the bottom of valley in echo height variation and the sound axis of ultrasonic probe decreases gradually as supply of oil becomes insufficient, and it becomes zero by running out of oil at a contact surface.

B29 2009年2月2日浅問山噴火に伴う量的降灰予測 : 気象レーダーにより観測された噴煙エコー頂高度の利用(遠隔観測の新手法,口頭発表)

B29 2009年2月2日浅問山噴火に伴う量的降灰予測 : 気象レーダーにより観測された噴煙エコー頂高度の利用(遠隔観測の新手法,口頭発表)

Observation of lubrication conditions using an ultrasonic technique

AbstractEvaluation of lubrication conditions for a real frictional surface, such as a steel bearing, becomes an important issue for safe operation of a machine. In this paper, an application of ultrasonic technique is attempted for a purpose of evaluating the lubrication conditions. Ultrasonic waves emitted towards a hydrodynamic lubrication interface are reflected multiple times in oil film, and an echo height of reflected waves from the boundary is dependent on film thickness. The results of this study indicated that the ultrasonic technique is able to measure film thickness of approximately 50 nm in the case of a standstill surface having extremely small surface roughness. Furthermore, a potential for estimating the oil film thickness between a piston ring and cylinder is also indicated. In addition, in the case of a ball bearing, quantitative measurement of a size of dent, which forms the origin of flaking, is important for an evaluation of lubrication conditions. This becomes possible with an observation of a change in the echo height reflected from a boundary surface between a housing and an outer ring of the ball bearing. In this study, quantitative measurement of an indentation having 0.32 mm width on a raceway surface of an inner ring was achieved. Copyright © 2009 John Wiley & Sons, Ltd.

Evaluation of thermal sprayed coating using ultrasonic inspection by means of bottom echo back reflection

Thermal spraying technique is widely used in various mechanical parts as a surface reforming technique. However, as demand to maintain superior mechanical performance in harsh operating environment increases, the need for non-destructive evaluation method for thermal spray coating becomes more important. For this purpose, we thinned the thickness of the thermal sprayed coating by abrasion with blasting and used ultrasonic inspection by means of bottom echo reflection for effective measurement of abrasion quantity in thermal sprayed coating. The results obtained are summarized as follows. When the thickness of thermal sprayed coating becomes thin, the echo height increases. This is because thermal sprayed coatings absorb ultrasonic energy. Ultrasonic energy absorbed by Al 2O 3 is smaller compared with Fe-13Cr coating. Thermal sprayed coatings submerged in water have a lower echo height compared with air. As mentioned above, the thermal sprayed coating thickness can be estimated using ultrasonic inspection by means of bottom echo back reflection.

31P Nuclear Spin Dynamics in Metallic Si:P at Very Low Temperature and High Magnetic Fields

Phosphorus-doped silicon (Si:P) is one of the most extensively studied condensed matter systems since a variety of physical phenomena accompanies with doping P in Si, such as impurity-band conduction, metal–insulator transition (M–I). Recently, it has attracted new interest for possible applications to quantum computer where P nuclear spins serve qubits and electron spins are completely polarized for isolated spins bound at the donor. This model of silconbased quantum computer requires NMR control of P nuclear spins under extreme conditions of several tesla magnetic field and millikelvin temperature. Spin dynamics of both nuclei and electrons are of great interest in this regard. However, despite a large amount of works devoted to the magnetic properties of Si:P, P-NMR has never been investigated under such experimental conditions. Here we present the P-NMR of metallic Si:P investigated at temperature between 40mK and 4K and a magnetic field of 7 T. We tried P-NMR in insulator Si:P but could not detect it. Our NMR data show several novel features in longitudinal relaxation time T1 and transverse relaxation time T2 associated with very low temperature and high magnetic field. We prepared a powdered sample from single crystalline silicon wafers with phosphorus dopant concentration of n 1⁄4 5:6 10 cm 3 which is above the critical concentration for M–I, nc ’ 3:7 10 cm . The dopant concentration of Si:P was determined by measuring room temperature resistivity with the Mousty scale. The sample was immersed in He–He mixture which was cooled by a dilution fridge. The NMR spectra at 120MHz were obtained by recording the spin-echo height with varying magnetic fields. The T2 was measured by decay of the echo height with varying time delay of the pulse sequence =2 . The T1 was obtained from the magnetization recovery after -pulse with varying waiting time t of the sequence t =2 . The NMR spectra were typical for metallic sample and did not depend on temperature. The linewidth of about 24mT and the Knight shift agree with those reported in the literature for similar dopant concentrations. The linewidth is believed to be determined by inhomogeneous broadening of hyperfine interactions. The longitudinal relaxation showed a substantial change only below 0.6K from the previous data. Nuclear magnetization was recovered in two steps, following double-exponential curves below 0.6K while the recovery followed single-exponential curves above 0.6K. Typical recovery curves are shown in the inset of Fig. 1. Below 0.6K, we obtained T1 separately for the fast and slow components of the relaxation, T1f and T1s. The T1f and T1s are plotted against temperatures in Fig. 1. T1f above 0.2K follows the Korringa’s relation as, T1T 1⁄4 ( is Korringa constant). It shows, however, a gradual deviation from the Korringa’s relation below 0.2K. The long T1s increases with decreasing temperature as T1s / T n with n ’ 1:3. A double-exponential form of recovery curve was observed only when the nuclear Zeeman bath decays through the electron bath to a third bath in series and the heat capacity of Zeeman bath, CN, becomes comparable to that of the electron bath, Ce. The second stage for the slow recovery process appeared in the magnetization recovery at T 1⁄4 0:6K when CN=Ce ’ 0:01 and [1 MðtÞ=M0] was measured in the range between 2 and 0.01. We understand that both the deviation of T1f from the Korringa’s relation and the appearance of long T1s arise from the large nuclear Zeeman heat capacity at high B=T . Because CN goes with ðB=TÞ while Ce with T , the temperature of electrons actually rises during nuclear spin relaxation when the electron system is decoupled to the third bath (He–He mixture bath) by T1s since T1f T1s. Due to heating up the electron temperature Te the nuclear spins relax at faster rate =Te than that expected from =T where Te > T . The T1s was first observed and was the time constant for the Zeeman and conduction electron baths to decay together to the He–He bath. The T1s is needed to cool down the nuclear spins at low temperatures and may be due to the Kapitza resistance between the sample and He–He mixture. Fig. 1. Longitudinal relaxation times T1f (circle) and T1s (square) with temperature. The inset shows the recovery curves. Dotted line represents the Korringa’s relation derived from the data above 1K. Solid line is a guide to the eye.

A chemical model of meteoric ablation

Abstract. Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD) is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K) through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides), and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si) have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K) does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s−1) and smallest (10−17–10−13 g) meteoroids, but makes a minor contribution to the overall ablation rate.

MEASUREMENT OF THIN OIL FILM THICKNESS USING ULTRASONIC TECHNIQUE

An application of ultrasonic technique is attempted for the purpose of measuring thin oil film thickness between two surfaces. The amplitude of the wave reflected from the boundary is vary depending on film thickness, because the ultrasonic wave emitted to the interface between two surfaces does multiple reflection and interference in oil film. Quantitative measurement of oil film thickness then can be possible. For instance, it is possible to measure the submicron film thickness which exists near the point contact formed by convex glass and plate with high frequency probe. And it is confirmed that the oil film thickness estimated from the echo height agrees with the film thickness decided by the curvature of the lens or obtained by the optical interference method, even if it is 100 nm. On the other hand, the thickness of oil film between cylinder and piston ring can be easily measured by setting the small ultrasonic probe on the back of piston ring. For example, the influence of the second ring and oil ring for the behavior of an oil film formed on a top ring is able to evaluate quantitatively. As mentioned above, it is cleared that quantitative evaluation of thin film thickness is possible with investigating the echo height obtained by ultrasonic wave pulse reflection method.

Ultrasonic behavior of plastically deformed and heat treated steel

Studies were made on the longitudinal ultrasonic velocity and its attenuation characteristics in medium carbon steel forging subjected to 0–60% hot upsetting followed by heat treatment. The fineness of ferrite and pearlite increased with increasing deformation and cooling rate during heat treatment. The area fraction of pearlite increased from 21% to 45% as well as the mean interlamellar spacing in pearlite decreased from 8.79 μm to 0.689 μm in the 40% deformed (upsetted) normalized sample It was observed that the ultrasonic velocity decreased with increasing degree of deformation. The velocity was found to be highest in the normalized steel acquiring a value of 5920 m/s and lowest in hardened steel acquiring a value of 4979 m/s. The attenuation decreased with increasing deformation resulting in increased back wall echo heights. The residual stresses on the surface of typical 60% deformed and annealed steel samples using x-ray diffractometry were measured to be — 39.7 MPa (compressive) and — 188.0 MPa (compressive) respectively.

Radar Backscatter from Underdense Meteors and Diffusion Rates

Many meteoroids burn up between about 120 km and 70 km, deposit metals and dust and form ionized trails which are detected by radars. Model studies about the influence of neutral or positively charged background dust on the ambipolar diffusion indicate that significant smaller decay times should be observed for weak meteor echoes compared to strong meteor echoes which can affect the estimation of temperatures. The variation of meteor decay times in dependence on echo strength, height, and season was studied using radar observations at 69° N, 22° S, and 67° S. Significantly reduced decay times were found for weak echoes below about 88 km at low latitudes throughout the year, and at high latitudes with the exception of summer. In summer at high latitudes, decreasing decay times of weak and strong meteors are observed at altitudes below about 85 km during the appearance of noctilucent clouds. The impact of reduced decay times on the estimation of neutral temperatures from decay times is discussed.

Evaluation of a Technique for Radar Identification of Large Hail across the Upper Midwest and Central Plains of the United States

Abstract Radar data were analyzed for severe thunderstorms that produced severe hail (>19 mm diameter) across the central and northern plains of the United States during the 2001–04 convective seasons. Results showed a strongly linear relationship between the 50-dBZ echo height and the height of the melting level—so strong that a severe hail warning methodology was successfully deployed at the National Weather Service Warning and Forecast Offices in North Dakota and Iowa. Specifically, for each of 183 severe hailstorms, the 50-dBZ echo height near the hail event time was plotted against the depth of the environmental melting level. Linear regression revealed a coefficient of determination of 0.86, which suggested a strong linear relationship between the 50-dBZ echo height and the melting-level depth for the severe hail producing storms. As the height of the melting level increased, the expected 50-dBZ echo height increased. A severe warning criterion for large hail was based on the 10th percentile from the linear regression, producing a probability of detection of 90% and a false alarm rate of 22%. Additional analysis found that the 50-dBZ echo-height technique performs very well for weakly to moderately sheared thunderstorm environments. However, for strongly sheared, supercell-type environments, signatures such as weak-echo regions and three-body scatter spikes led to more rapid severe thunderstorm detection in many cases.

P-42 Measurement of lubrication condition and oil film thickness with using ultrasonic technique

An application of ultrasonic technique is attempted for the purpose of measuring film thickness between moving surfaces. The measurement of film thickness is possible only by setting the ultrasonic probe to one of the friction surface, and the drilling for installing the probe like a measurement using a displacement sensor is not conducted. The ultrasonic wave emitted to the hydrodynamic lubrication interface is reflected multiple in oil film, and the echo height of reflected wave from the boundary is dependent on film thickness. For example, the thickness of oil film between cylinder and piston ring can be easily measured only by setting the small ultrasonic probe on the back of piston ring. On the other hand, the echo height under the mixed lubrication region is mainly dependent on the solid contact area. Therefore, the load share rate at the solid contact parts can be estimated from observed echo height.

Ultrasonic Testing Method for Detection of Planar Flaws in Graphite Material

An ultrasonic inspection method for a graphite ingot was developed to detect internal planar flaws that are oriented in various directions; this method is necessary to perform quality assurance of throat inserts of solid rocket motors. Major problems that are unique to this graphite inspection were solved. An ultrasonic beam in graphite shows uneven propagation behavior both within and among individual ingots. That individual unevenness engenders variation in echo heights of flat-bottomed holes, which can be compensated through two-dimensional scanning accompanying a change in incident angles of two directions. This scanning procedure is therefore necessary to detect internal planar flaws that orient in various directions. The unevenness among ingots can be compensated by measuring the wave velocity and attenuation coefficient in the test block itself before inspection. A test block including artificial internal flaws was fabricated and inspected using the developed method. It was then sliced into several thin disks. The sliced disks were inspected using the conventional ultrasonic testing method using a normal beam technique. The two methods detected identical flaws, thereby validating the developed method. The technique described here has been enacted as JIS Z 2356 under the title, ‘‘Method of automatic ultrasonic inspection for graphite ingot’’. [doi:10.2320/matertrans.I-MRA2007851]

Characteristics of Tropical Convection over the Ocean near Kwajalein

Abstract Radar observations have been analyzed to determine characteristics of convection over the oceanic region around Kwajalein in the tropical western Pacific. Generally, the echo areas, heights, and durations exhibited lognormal distributions. Heights were greater under conditions of higher midtropospheric humidity and correlated with echo area, with a wide spread of values. Mergers and splits often truncated echo lifetimes. The most surprising result was the distribution of orientation angles of echo lines, which statistically verify the shear-parallel and shear-normal modes of convective line organization seen elsewhere over tropical oceans. The two modes typically coexisted within the area of radar coverage, indicating a potential difficulty in predicting line orientation in terms of large-scale variables. The largest members of the echo population were mesoscale convective systems (MCSs), which had large stratiform components. They occurred in environments of increased humidity and higher midlevel buoyancy associated with westward-propagating synoptic-scale disturbances. MCSs moved with the easterlies in low to midlevels and exhibited the jump updraft, overturning updraft, and subsiding midlevel inflow characteristic of tropical oceanic MCSs. The Kwajalein Experiment (KWAJEX) radar echo population resembles that of the eastern tropical Atlantic in terms of the shapes of the distributions of area, height, and lifetime, the prevalence of echo mergers and splits, and the tendency to form shear-parallel and shear-normal lines. These characteristics appear to be endemic to oceanic convective populations. Large-scale conditions appear to modulate these basic population characteristics rather than qualitatively alter them.

Membrane Curvature Change Induced by an Antimicrobial Peptide Detected by 31P Exchange NMR

The influence of an antimicrobial peptide, protegrin-1 (PG-1), on the curvature and lateral diffusion coefficient (D(L)) of phosphocholine bilayers is investigated using one- (1D) and two-dimensional (2D) (31)P exchange NMR. The experiments utilize the fact that lipid lateral diffusion over the curved surface of vesicles changes the molecular orientation and thus the (31)P chemical shift anisotropy. This reorientation is manifested in 2D spectra as off-diagonal intensities and in 1D stimulated-echo experiments as reduced echo heights. The 2D spectra give information on the reorientation-angle distribution while the decay of the stimulated-echo intensity, which closely tracks the second-order correlation function in our experiments, yields the correlation times of the reorientation. The relationships among the 2D exchange spectra, stimulated-echo intensities, the correlation function, and reorientation-angle distributions are analyzed in detail. In the absence of PG-1, both dilaurylphosphotidylcholine (DLPC) and palmitoyloleoylphosphatidylcholine (POPC) vesicles show biexponential decays of the stimulated-echo intensities to equilibrium values of 0.20-0.25, suggesting that the curvature of the lipid vesicles has a bimodal distribution. The addition of PG-1 to DLPC vesicles increased the decay time constants, indicating that D(L) decreases due to peptide binding. In contrast, the addition of PG-1 to POPC vesicles decreased the decay constants by three to fivefold, indicating that the POPC vesicles are fragmented into smaller vesicles. On the basis of the changes in D(L) and the decay constants, we estimate that the radius of the POPC vesicles decreases by threefold due to PG-1 binding. Simulations of the 2D exchange spectra yielded quantitative reorientation-angle distributions that are consistent with the bimodal distributions of the vesicle curvature and the effects of the peptide on the two types of lipid bilayers. Thus, (31)P exchange NMR provides useful insights into the membrane morphological changes induced by this antimicrobial peptide.