Concrete cracks which are gradually extended, damaged and destructed by the load have become difficult to be solved in
engineering. Due to the advantages of convenient production, high sensitivity, reasonable performance-price ratio, selfsensing,
piezoelectric ceramic (such as PZT) smart aggregates used as sensor and actuator are embedded in the
reinforced concrete beams to generate sin-sweep excitation signals on-line and detect real-time signals with digital
oscilloscope before and after damage. The optimal extraction damage signals are extracted and statistical pattern
recognition algorithm of wavelet decomposition about the detection signals is established by wavelet analysis and
statistical characteristics analysis. The statistical distribution of signal amplitude and the relevant damage indicators are
proposed for the use of active health monitoring and energy damage principles. The results of loading tests show that the
amplitude of active monitoring signal produced a larger attenuation after damage and sweep wave signals used in active
health monitoring are effective in identifying the different health status of structure. The statistical pattern recognition
algorithm based on wavelet packet decomposition can effectively detect crack damages of concrete structure. This
technology may open a new road for active and permanent monitoring and damage detection on line as well as
development of active health monitoring system based on probability statistics of piezoelectric concrete.
The technique of structure health monitoring (SHM) has become a reaching hotspot in civil engineering field at present.
The successful application of smart materials in this field has greatly promoted the development of the SHM. Among the
smart materials, the piezoelectric material has been paid much attention for its good characteristic and low price. The
well competitive properties have had a wide application prospect in SHM field. In this paper, the crack monitoring
technique for concrete columns using piezoceramic transducers was experimentally developed. In the experiment, the
piezoceramic transducers were embedded into two concrete columns under the large and small eccentric compression
loads, respectively. The acoustic emission was used for the identification of the crack generation and development. For
the detection of the crack level, a wave-based method for the damaged columns was used and the damage level was
determined by compare of the health and damage signals. The experimental results show that acoustic emission based on
piezoceramic transducers can be used in the crack monitoring of reinforced concrete structure.
According to the characters of smart piezoelectric concrete structures, the structure health monitoring strategy was
researched in the paper in details including three basic contents. Firstly, it was proposed that the placement of
piezoelectric transducers in the form of an array. The problem of the distance between adjacent transducers was also
discussed. Secondly, several forms of detecting signals, frequency band and modes of the transmitting signals were
pointed out in the paper. At last, a feasible damage identification method was proposed. The method combined the
wavelet packet analysis with the root-mean-square deviation to evaluate the damage level. Especially, when analyzing
the damage location, a concept of a transducer array resolution was proposed and used in the damage identification. The
transducer array divided the structure into many sub-regions where the damage locations were approximately
determined. The accuracy of the damage location will be better and finer with the increasing of the transducer array
We have developed an Atomic Force / Photon Scanning Tunneling Microscope (AF/PSTM) to eliminate the optical false image caused by topography of sample in PSTM. The key element of this system is bi-functional bent optical fiber probe, which can both be an optical cantilever and a device to collect the evanescent wave in near field of samples. In this paper, we derived a method to fabricate the bi-functional bent optical probes of AF/PSTM using communication optical fibers. The heated pulling combined with chemical etching method is proposed and developed. Fiber probes with an apex having a diameter smaller than 100nm could be produced with a controlled cone angles vary from 40 to 90 degrees. The back of the probe is finally coated with aluminum to enhance the reflection and with SiO2 to prevent Al film from oxidating in the atmosphere. This method is straightforward and fast. Using probes made with this method, the images of biology samples are obtained and the image separation is realized.
With the fast development of scanning probe microscope, especially atomic force microscope (AFM), an imaging tool for life sciences researches is provided. Biological species imaging is one of the fundamental studies in life sciences, so it becomes one of the most important applications of AFM imaging. In this paper, AFM images of proteus species separately by contact-mode and intermittent-contact MacMode are obtained and investigated, and also are compared with its image of scanning electron microscope (SEM). Note that flagella are presented in SEM image while no evidence of flagella is observed when proteus species were imaged in AFM. This difference may be having something to do with sample preparation. The other possibility of this difference is that the proteus species which imaged was immature. Moreover, the images by MacMode in liquid medium show the outer surface of proteus species is smooth while the images by contact-mode in air show folding of the surface. The latter has clearly greater resolution than the former.
Our research group has recently developed a new type scanning probe microscope —AF/ PSTM. Using this setup, the optical false image caused by the inclination of sample surface can be eliminated; the optical image and the topography image are separated; and also two optical images (refractive index image, transmittivity image) and two AFM images (topography image, phase image) are obtained during one scanning. As a primary biologic application, this setup is engaged in the imaging of some biologic samples. The primary images ofthese biologic samples are obtained. Due to the advantage of AFIPSTM, four images can be acquired at the same time during one scanning. Consequently more information ofsample is given by comparing these images. This work shows that the AF/PSTM may be improved to be a useful tool in biology research.
KEYWORDS: Refractive index, Patents, Magnesium fluoride, Glasses, Photography, Atomic force microscopy, Near field scanning optical microscopy, Scanning tunneling microscopy, Photonic microstructures, Near field optics
According to author's Chinese invented patent ZL96 I II 979.9 named "The method of separating image of AF/PSTM (atom force and photon scanning tunneling microscope)", the first system ofAF/PSTM has been developed. Its principle, photograph, block diagram and some images ofan examination sample have been given in this paper. There are three advantages of this system: (1) AF/PSTM can eliminate the optical false image which caused by topography of sample in PSTM; (2) The optical images and topographic image of sample are separated with this AF/PSTM; (3) From once scanning imaging two optical images (refractive index image and transmissivity image) and two AFM images (topography image and phase or grads oftopography image) can be obtained.