Determination of the Ultrasonic Velocity on a Recent and Aged Pine Wood

Aging in wood is the inevitable modification of physical and mechanical properties due to deterioration caused by different factors such as organisms that destroy wood, photodegradation, weathering or long-term loading. During the wood degradation process, significant mass, stiffness and strength are lost. Therefore, it is relevant to monitor the wood decomposition process to guarantee the structural requirements in buildings. This research work aims to report the influence of degradation in wood due to deterioration through the use of ultrasonic measurements. Longitudinal and transverse ultrasonic velocities were calculated using the ultrasonic emission-transmission technique for aged and unaged Mexican pine (Pinus Strobus) wood. The experimental measurements were carried out using longitudinal and shear wave ultrasonic transducers with a center frequency of 1.0 MHz and 0.5MHz respectively. Scanning electron microscopy (SEM) was performed to establish a direct correlation with the behavior of the ultrasonic wave developed in naturally aged and unaged wood. Measurements revealed higher ultrasonic velocity values for unaged wood samples in longitudinal, tangential and radial directions compared to aged wood samples, but no significant differences were found in all other wood directions.

Detection of Self-Healing Discharge in Metallized Film Capacitors Using an Ultrasonic Method

Benefiting from self-healing features, metallized film capacitors (MFCs) are widely employed to compensate reactive power (VAR) and thus improve the performance of AC systems. To ensure the aforementioned functions, self-healing testing is a compulsory quality inspection for every type of MFC. In 2014, the International Electrotechnical Commission (IEC) issued a standard that recommended a general and instructive test procedure based on audible noise or ultrasound signals. However, more details relevant to this high voltage (HV) test were not provided. In this paper, we focused on the ultrasonic detection technique to reveal the self-healing characteristics of two typical MFCs. By launching a series of HV tests with star and delta MFCs, the waveform features, discharge energy, and spectrum distributions were analyzed. It was observed that the partial discharge always occurs before self-healing discharge with the same spectrum features ranging above 40 kHz. To solve the entanglement of these two discharge processes, a relative amplitude difference method is proposed. Based on the experimental observations, a detection algorithm incorporated with the ultrasonic emission sensors, preamplifier, and high-speed A/D converter was developed to assist the self-healing performance test.

Quantitative approaches to sensory information encoding by bat noseleaves and pinnae

The biosonar systems of horseshoe bats (Rhinolophidae) and Old World round leaf-nosed bats (Hipposideridae) incorporate a pervasive dynamic at the interfaces for ultrasound emission (noseleaves) and reception (pinnae). Changes in the shapes of these structures alter the acoustic characteristics of the biosonar system and could hence influence the encoding of sensory information. The focus of the present work is on approaches that can be used to investigate the hypothesis that the interface dynamic effects sensory information encoding. Mutual information can be used as a metric to quantify the extent to which the different ultrasonic emission and reception characteristics (beampatterns) provide independent views of the environment. Two different quantitative approaches have been taken to evaluate the relationship between dynamically encoded additional sensory information and sensing performance in finding the direction of a biosonar target. The first approach is to determine an upper bound on the number of different directions that can be distinguished by virtue of distinct spectral signatures. The second approach is based on a lower bound (Cramér–Rao) on the variance of direction estimates. All these different metrics demonstrate that the peripheral dynamics seen in bats result in the encoding of additional sensory information that is suitable for enhancing biosonar performance.

Evidence for Air-Seeding: Watching the Formation of Embolism in Conifer Xylem

Water transport in plants is based on a metastable system as the xylem “works” at negative water potentials (ψ). At critically low ψ, water columns can break and cause embolism. According to the air-seeding hypothesis, this occurs by air entry via the pits. We studied the formation of embolism in dehydrating xylem sections of Juniperus virginiana (Cupressaceae), which were monitored microscopically and via ultrasonic emission analyses. After replacement of water by air in outer tracheid layers, a complex movement of air-water menisci into tracheids was found. With decreasing ψ, pits started to aspirate and the speed of menisci movements increased. In one experiment, an air-seeding event could be detected at a pit. The onset of ultrasonic activity was observed when pits started to close, and ultrasonic emission ceased at intense dehydration. Experiments clearly indicated that predictions of the air-seeding hypothesis are correct: At low ψ, pit mechanisms to prevent air entry failed and air spread into tracheids. ψ fluctuations caused complex movements of air-water menisci and pits, and at low ψ, air-seeding caused ultrasonic emissions. Main insights are presented in a video.

Design of Ultrasonic Ranging Alarm Device Based on SN8P2501B

Introduced one ultrasonic ranging alarm device based on SN8P2501B microcomputer, it mainly included ultrasonic emission circuit, receiving circuit, keyboard, alarm circuit and the software. Compared with the traditional ranging methods, the system used 555 time-base circuit to produce ultrasonic, and designed a temperature compensation circuit to eliminate effect of sound velocity produced by the environment temperature. The practical application results show that the ranging system is stable , reliable and highly accurate, so the technology and methods adopted in the system are highly practical and worthy of being used abroad.

The Quantification Research of Engine Body Defect that Tested by Ultrasonic Phased Array

After a long run, the places of body cooperate with valve very easy to produce fatigue cracks. This cracks if not detected, extremely easy to have the accident. As the most commonly used testing equipment, ultrasonic nondestructive testing is often used to detect the engine body. However, most of the existing ultrasonic nondestructive testing equipment is used to detect whether there is a defect, there is little research the specific size of defects. According to the principle of ultrasonic emission, theoretical calculation and combined with test block, get the body phased array detection method.