Wideband acoustic activation and detection of droplet vaporization events using a capacitive micromachined ultrasonic transducer

An ongoing challenge exists in understanding and optimizing the acoustic droplet vaporization (ADV) process to enhance contrast agent effectiveness for biomedical applications. Acoustic signatures from vaporization events can be identified and differentiated from microbubble or tissue signals based on their frequency content. The present study exploited the wide bandwidth of a 128-element capacitive micromachined ultrasonic transducer (CMUT) array for activation (8 MHz) and real-time imaging (1 MHz) of ADV events from droplets circulating in a tube. Compared to a commercial piezoelectric probe, the CMUT array provides a substantial increase of the contrast-to-noise ratio

Design of all-pole low-pass ladder filters using current-mode damped integrators

A method for operational simulation of all-pole low-pass LC ladders filters by using current-mode damped integrators is introduced. The circuits obtained by this method need only current mirrors and capacitors and are convenient for realization in CMOS technology as well as can be used in other technologies

An endoscopie imaging system based on a two-dimensional CMUT array: real-time imaging results

Real-time catheter-based ultrasound imaging tools are needed for diagnosis and image-guided procedures. The continued development of these tools is partially limited by the difficulty of fabricating two-dimensional array geometries of piezoelectric transducers. Using capacitive micromachined ultrasonic transducer (CMUT) technology, transducer arrays with widely varying geometries, high frequencies, and wide bandwidths can be fabricated. A volumetric ultrasound imaging system based on a two-dimensional, 16×l6-element, CMUT array is presented. Transducer arrays with operating frequencies ranging from 3 MHz to 7.5 MHz were fabricated for this system. The transducer array including DC bias pads measures 4 mm by 4.7 mm. The transducer elements are connected to flip-chip bond pads on the array back side with 400-μm long through-wafer interconnects. The array is flip-chip bonded to a custom-designed integrated circuit (IC) that comprises the front-end electronics. Integrating the front-end electronics with the transducer array reduces the effects of cable capacitance on the transducer's performance and provides a compact means of connecting to the transducer elements. The front-end IC provides a 27-V pulser and 10-MHz bandwidth amplifier for each element of the array. An FPGA-based data acquisition system is used for control and data acquisition. Output pressure of 230 kPa was measured for the integrated device. A receive sensitivity of 125 mV/kPa was measured at the output of the amplifier. Amplifier output noise at 5 Mhz is 112 nV/√Hz. Volumetric images of a wire phantom and vessel phantom are presented. Volumetric data for a wire phantom was acquired in real-time at 30 frames per second.Publisher's Versio

Ultrasound Nondestructive Evaluation (NDE) Imaging with Transducer Arrays and Adaptive Processing

This paper addresses the challenging problem of ultrasonic non-destructive evaluation (NDE) imaging with adaptive transducer arrays. In NDE applications, most materials like concrete, stainless steel and carbon-reinforced composites used extensively in industries and civil engineering exhibit heterogeneous internal structure. When inspected using ultrasound, the signals from defects are significantly corrupted by the echoes form randomly distributed scatterers, even defects that are much larger than these random reflectors are difficult to detect with the conventional delay-and-sum operation. We propose to apply adaptive beamforming to the received data samples to reduce the interference and clutter noise. Beamforming is to manipulate the array beam pattern by appropriately weighting the per-element delayed data samples prior to summing them. The adaptive weights are computed from the statistical analysis of the data samples. This delay-weight-and-sum process can be explained as applying a lateral spatial filter to the signals across the probe aperture. Simulations show that the clutter noise is reduced by more than 30 dB and the lateral resolution is enhanced simultaneously when adaptive beamforming is applied. In experiments inspecting a steel block with side-drilled holes, good quantitative agreement with simulation results is demonstrated

İnşaat sektöründeki tedarikçilerin uyguladıkları stratejiler üzerine marmara bölgesinde bir araştırma

ÖZET21. yüzyılda gittikçe artan bir ivmeyle gelişmekte olan pazarlarda, modern iş dünyasındaki firmalar da yaygın ve hızlı bir değişime uğramaktadır. Bu değişimin ortasında çaresiz ve geride kalmamak için firmaların, sektörlerinin farkında olup gelebilecek tehditlere karşı hazır bulunmak ve sektör içerisinde kendilerini var etmeye devam edebilmek için geliştirdikleri yönetim departmanlarının, bu amaçla uyguladıkları stratejiler bulunmaktadır. Bir firmanın, amaç ve hedeflerine ulaşabilmesi için yaptığı planlar ve izlediği yollar anlamında kullanılan strateji tanımı, özellikle firmaların rakiplerine karşı üstünlük sağlayabilmesi ve sektör içerisinde iyi bir pozisyon edinerek fark edilebilmesi için kullanılır. İnşaat konusunda giderek artan bilgi ve beceriler, talep edilen yapıların çeşitlenmesini ve karmaşıklaşmasını da beraberinde getirmiştir. Yapılardaki karmaşıklık arttıkça, çok sayıda farklı alandan katılımcının bir araya geldiği inşaat sektörü de giderek komplike hale gelip büyümekte, katılımcıları çoğalmakta, dolayısıyla inşaat sektörü içerisindeki firmalar için, gelecekteki performanslarını bugünden yönetebilme, karlılık ve verimliliklerini artırma, dolayısıyla rekabet stratejileri oluşturma konuları zorunlu hale gelmektedir. Bu çalışmada, öncelikle strateji kavramına tarihsel gelişimi içerinde yer verilmiş, daha sonra oldukça karmaşık bir yapıya sahip inşaat sektörünün genel analizi ile birlikte sektördeki ilişkilerin tedarikçiler ve müşterilerine odaklanılarak incelemesi gerçekleştirilmiştir. Tezin araştırma kısmında ise Marmara Bölgesi özelindeki inşaat tedarikçilerine yönelik bir anket uygulaması gerçekleştirilerek, inşaat sektöründeki tedarikçilerin uyguladıkları stratejiler, daha önce irdelenen yaklaşım ve modeller ışığında araştırılmıştır. Araştırma sonuçları inşaat sektörü tedarikçileri içerisinden belirlenen firmaların seçtikleri ve uyguladıkları stratejilerin, gerektiği gibi verimli işleyip işlemediği, bu stratejilerin firmaya ne gibi yarar ve varsa zararlar getirdiğine ilişkin sınırlı çıkarımlar yapmaya olanak sağlamaktadır. Anahtar Sözcükler: İnşaat sektörü, tedarikçi stratejileri, Hamel ve Prahalad yaklaşımı, Porter yaklaşımı, Slywotzky yaklaşımı, Grove yaklaşımı.ABSTRACTAs of 21st century, firms operating in modern world change continuously and at speed along markets possessing a great development momentum. So as to keep up with the change, the management departments of the firms apply certain strategies, which help them keep ready against threats and risks within their sectors. Strategy, which is a compilation of plans and means for a firm to help it realize its goals, is used for competitive strength and reaching a good sector position by the firms. The increasing quantities of knowledge and skills with respect to construction have brought diversification of demanded buildings and complexity with as well. As complexity goes up, construction sector grows through complex procedures with rising number of contributors that lead the construction firms to be able to manage their future potentials from today, to up their profitability and efficiency, which all necessitate formation of competition strategies. From this point of view, this research focuses on strategy and its evolution in time; strategies pertaining to management were focused upon, followed by the analysis of complex structure of construction sector. After that, the strategies applied by suppliers within construction sector have been analyzed with a survey on suppliers from Marmara region of Turkey; to be concluded by final analyses on the state and future of the relationship between the suppliers and their customers.Keywords: Construction sector, supplier strategies, Hamel and Prahalad approach, Porter approach, Slywotzky approach, Grove approach

Fabrication of vacuum-sealed capacitive micromachined ultrasonic transducers with through-glass-via interconnects using anodic bonding

WOS: 000397049500023This paper presents a novel fabrication method for vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays that are amenable to 3D integration. This paper demonstrates that MEMS structures can be directly built on a glass substrate with preformed through-glass-via (TGV) interconnects. The key feature of this new approach is the combination of copper through-glass interconnects with a vibrating silicon-plate structure suspended over a vacuum-sealed cavity by using anodic bonding. This method simplifies the overall fabrication process for CMUTs with through-wafer interconnects by eliminating the need for an insulating lining for vias or isolation trenches that are often employed for implementing through-wafer interconnects in silicon. Anodic bonding is a low-temperature bonding technique that tolerates high surface roughness. Fabrication of CMUTs on a glass substrate and use of copper-filled vias as interconnects reduce the parasitic interconnect capacitance and resistance, and improve device performance and reliability. A 16x16-element 2D CMUT array has been successfully fabricated. The fabricated device performs as the finite-element and equivalent circuit models predict. A TGV interconnect shows a 2-Omega parasitic resistance and a 20-fF shunt parasitic capacitance for 250-mu m via pitch. A critical achievement presented in this paper is the sealing of the CMUT cavities in vacuum using a PECVD silicon nitride layer. By mechanically isolating the via structure from the active cells, vacuum sealing can be ensured even when hermetic sealing of the via is compromised. Vacuum sealing is confirmed by measuring the deflection of the edge-clamped thin plate of a CMUT cell under atmospheric pressure. The resonance frequency of an 8-cell 2D array element with 78-mu m diameter circular cells and a 1.5-mu m plate thickness is measured as 3.32 MHz at 15-V dc voltage (80% Vpull-in).National Science Foundation, National Nanotechnology Coordinated Infrastructure (NNCI) [ECCS-1542015]; State of North Carolina; National Science Foundation [ECCS-1542015]The authors would like to thank Tim Mobley and John Maki from Triton Microtechnologies for helping with the fabrication of TGV substrates. The device fabrication was performed in part at the NCSU Nanofabrication Facility (NNF), a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), which is supported by the National Science Foundation (Grant ECCS-1542015) as part of the National Nanotechnology Coordinated Infrastructure (NNCI). The device characterization was performed in part at the Analytical Instrumentation Facility (AIF) at North Carolina State University, which is supported by the State of North Carolina and the National Science Foundation (award number ECCS-1542015). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI)

A three-mask process for fabricating vacuum-sealed capacitive micromachined ultrasonic transducers using anodic bonding

WOS: 000354455100017PubMed ID: 25965687This paper introduces a simplified fabrication method for vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using anodic bonding. Anodic bonding provides the established advantages of wafer-bonding-based CMUT fabrication processes, including process simplicity, control over plate thickness and properties, high fill factor, and ability to implement large vibrating cells. In addition to these, compared with fusion bonding, anodic bonding can be performed at lower processing temperatures, i.e., 350 degrees C as opposed to 1100 degrees C; surface roughness requirement for anodic bonding is more than 10 times more relaxed, i.e., 5-nm root-mean-square (RMS) roughness as opposed to 0.5 nm for fusion bonding; anodic bonding can be performed on smaller contact area and hence improves the fill factor for CMUTs. Although anodic bonding has been previously used for CMUT fabrication, a CMUT with a vacuum cavity could not have been achieved, mainly because gas is trapped inside the cavities during anodic bonding. In the approach we present in this paper, the vacuum cavity is achieved by opening a channel in the plate structure to evacuate the trapped gas and subsequently sealing this channel by conformal silicon nitride deposition in the vacuum environment. The plate structure of the fabricated CMUT consists of the single-crystal silicon device layer of a silicon-on-insulator wafer and a thin silicon nitride insulation layer. The presented fabrication approach employs only three photolithographic steps and combines the advantages of anodic bonding with the advantages of a patterned metal bottom electrode on an insulating substrate, specifically low parasitic series resistance and low parasitic shunt capacitance. In this paper, the developed fabrication scheme is described in detail, including process recipes. The fabricated transducers are characterized using electrical input impedance measurements in air and hydrophone measurements in immersion. A representative design is used to demonstrate immersion operation in conventional, collapse-snapback, and collapse modes. In collapse-mode operation, an output pressure of 1.67 MPapp is shown at 7 MHz on the surface of the transducer for 60-V-pp, 3-cycle sinusoidal excitation at 30-V dc bias.Defense Advanced Research Projects Agency [D13AP00043]; National Science Foundation [1160483]; National Institutes of Health [HL117740]This work was supported by the Defense Advanced Research Projects Agency under contract D13AP00043, by the National Science Foundation under grant 1160483, and by the National Institutes of Health under grant HL117740