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With a tremendous increase in mobile and wearable devices, the study of sensor-based activity recognition has drawn a lot of attention in the past years. In recent years, the applications of Human Activity Recognition are getting more and more attention, especially in eldercare and healthcare as an assistive technology when combined with the Internet of Things. In this paper, we propose three deep learning approaches to improve the accuracy of activity detection on the WISDM dataset. Particularly, we apply a convolutional neural network to extract the interesting features, then we use softmax function, support vector machine, and random forest for classification tasks. The results show that the hybrid algorithm, convolutional neural network combined with the support vector machine, outperforms all the previous methods in classifying every activity. In addition, not only the support vector machine but also the random forest shows better accuracy in classification task than the neural network classification and the former approaches do.

This paper reviews our work on the development of microwave carbon nanotube resonator sensors for gas detection. The sensor consists of a radio frequency resonator coated with a layer of carbon nanotubes. Upon exposure to gasses, the resonant frequency of the sensor shifts to indicate the presence of gasses. Our experimental results demonstrate that the microwave carbon nanotube resonator sensor achieves a sensitivity of 4000 Hz/ppm upon exposure to ammonia and the resonant frequency is recovered when ammonia is evacuated. The sensing mechanism is dependent on electron transfer from the ammonia to the nanotubes. This sensor platform has great potential for wireless sensing network applications.

Our study starts from the interaction of a thin liquid layer and surface acoustic waves in an isotropic semi-infinite substrate, and we obtain the relationship between wave velocity and thickness of ideal fluid layer. This result is similar with earlier experimental and research results. We further extend substrate to an isotropic semi-infinite plate, at which both symmetric and anti-symmetric modes of a plate can be captured as thickness of liquid layer becomes extremely thin. This result is very close to plate vibrations without the liquid layer. Finally, we analyze the characteristics of surface acoustic waves propagating in an anisotropic semi-infinite solid and plates covered with an ideal liquid layer. It is observed from an ST-cut quartz crystal substrate that there are many displacement modes and corresponding velocities due to the interaction of waves in the plate and liquid layer.

By energy trap theory and normalized criterion, we analyze the rationality of Mono-base integrate quartz resonator force sensor dimension structure, and the vibration characteristic of different structure. The result of theory analysis is consistent with experiment nearly. We find out the optimal integrate dimension structure of AT cut quartz resonator which frequency is 10 million. Based on this optimal structure, a differential frequency quartz resonator sensor is made which improves the temperature effect largely.

The feasibility of a piezoelectric quartz Cuprum (II) sensor based on a molecularly imprinted σ-PD is described. The Cuprum (II) sensor was devised by depositing the polymer onto one side of an Pt-cut quartz crystal through an electro-polymerization process. The author screened the factors which affect the electrochemical polymerization reaction, such as the concentration of template molecule and the concentration of monomer. The sensor showed high selectivity and sensitivity in aqueous system. The sensor response exhibited a linear relationship between frequency shift and the Cuprum (II) concentration in the range of 10-5~10-4 mol/L and the detection limit was 10-6mol/L.

MEMS research has been carried out through industry-university (Tohoku) collaboration for practical applications. Sophisticated devices such as electrostatically levitated rotational gyroscope, MEMS relay for wafer level packaging, array MEMS including multi-probe data storage and multi-column electron beam lithography system, small diameter fiber optic pressure sensor and SiC micro structure for glass press molding, have been developed. Electrical feedthroughs in glass play important role in the wafer level packaging and array MEMS. Materials such as conductive polymer for recording media, carbon nanotube for electron field emitter, SiC for harsh environment are used in these MEMS because of their unique features.

A cantilever beam and fiber Bragg grating is used to measure acceleration. The cantilever induces strain on the grating resulting in a Bragg wavelength modification that is subsequently detected. The output signal is insensitive to temperature variations and for a temperature change from −20°C to 40 °C, the output signal fluctuated less than 5% without any temperature compensation schemes. Because the sensor does not utilize expensive and complex demodulation techniques it is potentially inexpensive. For the experimental system a linear output range of 8 g could be detected.

We propose a new Dynamic Address Assignment Protocol for wireless sensor networks. This new protocol is based on the Dynamic Host Configuration Protocol and is modified into wireless sensor networks. The protocol aims to increase the flexibility and agility of wireless sensor networks with changing the amount of sensor nodes in sensor networks system easily. It is well suit for large-scale wireless sensor networks which update their sensor nodes frequently. The goals are achieved by assigning address dynamically and registering in collectors. We present an implement on wireless sensor network and evaluate our approach by discussing the payload ability of a wireless node.

With the advancements of networking technologies and miniaturization of electronic devices, wireless sensor networks (WSN) have become an emerging area of research in academic, industrial, and defense sectors. Sensors combined with low power processors and wireless radios will see widespread adoption in the new future for a variety of applications including battlefield, hazardous area, and structural health monitoring. However, many issues need to be solved before the full-scale implementations are practical. Among the research issues in WSN, security is one of the most challenging. Securing WSN is challenging because of the limited resources of the sensors participating in the network. Moreover, the reliance on wireless communication technology opens the door for various types of security threats and attacks. Considering the special features of this type of network, in this chapter we address the critical security issues in wireless sensor networks. We discuss cryptography, steganography, and other basics of network security and their applicability to WSN. We explore various types of threats and attacks against wireless sensor networks, possible countermeasures, and notable WSN security research. We also introduce the holistic view of security and future trends for research in wireless sensor network security.

Briefly, in this chapter we will present the following topics:

• Basics of security in wireless sensor networks.

• Feasibility of applying various security approaches in WSN.

• Threats and attacks against wireless sensor networks.

• Key management issues.

• Secure routing in WSN.

• Holistic view of security in WSN.

• Future research issues and challenges.

This paper develops a cable-less pipeline robot which can adapt to the change of pipe diameter. It introduces the composition and function of robot mechanism as well as control system in detail. In this study, the robot employs the crawler traveling mechanism with symmetrical distribution in three groups. Through the rotating of ball screw and the change of the quadrilateral structure both driven by the stepper motor, the radial dimension of robot will be changed. The control system of pipeline robot adopts the modularized design method, takes stm32f103 as its embedded processor, provides a variety of hardware functions as well as the expansion of the circuit interfaces, has a high versatility and applicability. Through verification, the designed pipeline robot can work in various environments of pipeline, realizing in-pipe detection, data acquisition as well as other functions.

The AT89C51 microcontroller is regarded as the control center in intelligent alarm system for fire, and the system can receive and take a treatment on the concentration and temperature signal of smoke output by the fire detector with sound-light alarm. It can monitor the temperature and smoke concentration, etc. by sending inspection signal to the site continually, and have a feedback to alarm controller constantly. The controller compares the accepted signal with the normal value in storage to judge and determine whether there is a fire. When the smoke and temperature in site are anomalies, or fire occurs, it can realize sound-light alarm, the set of alarm limit of smoke concentration and temperature, self-diagnosis breakdown, delayed alarm, etc., which has a certain practical value.

In this paper, an autonomous calibration method for sensor of navigation satellite is presented. Based on the requirement of pointing to earth, the sensors are calibrated by use of the ephemeris, and a calibration scheme designed to prevent random noise influence. The on-orbit data verification indicates the availability and feasibility of the method, and it is easy to realize in onboard software.

A new type of the piezoelectric cantilever force sensor is designed in this paper. According to the mechanics of materials, the bending stress of the piezoelectric cantilever subjected to a concentrated force on its one end is calculated, and then using the electromagnetic theory and piezoelectricity, the boundary surface charge by bending is obtained. Based on theoretical analysis of the bound charge distribution, the measuring electrodes are effectively disposed on the surfaces of the piezoelectric quartz disc and the measuring cell consists of only two Y0°-cut discs. Finally a specially designed experimental is performed to verify that the polar charge is linear with the external force.

Zinc oxide (ZnO) nanostructured surfaces can be reversibly altered from hydrophobicity to hydrophilicity in response to ultraviolet light or plasma treatment. In this paper, a thermal annealing procedure was used to tune ZnO nanowires' surface wettability, and the switchable reversible wettability was achieved. ZnO nanowires were synthesized by a simple solution method. The surfaces of as-synthesized ZnO nanowires demonstrated a superhydrophobicity with water contact angle of 151°. After a high temperature treatment (>300°C) for 20 minutes, their superhydrophobicity was transited to superhydrophilicity with water contact angle of < 10°. It was noted that this transition was very short (less than half minutes) when the annealing temperature is more than 400 °C. The high-thermal annealed superhydrophilic ZnO surfaces were recovered to superhydrophobicity after a low-temperature (~100 °C) procedure in 4 days. Thus, the tunable properties of ZnO surface energy result in reversible wettability between superhydrophobicity and superhydrophilicity. This tunable wettability can be explained based on ZnO as a semiconductor material, which provides different numbers of oxygen vacancies under different temperatures. This result will extend applications of ZnO nanomaterials to many important fields, such as microfluidic devices, chemical sensors and biosensors.

This study proposed a novel design of intelligent pacifier, in order to help the caretakers knowing when to feed the newborn infants or premature infants who do not have sufficient sucking ability. By adopting the inherent safety and TRIZ methods, the inherent safety analysis and design could effective prevent the injuries caused by improper feeding. Furthermore, Su-Fields Analysis was performed to identify the problems, and 76 Standard Solutions were used to find the possible design structure for systematic innovative design. The intelligent pacifier was designed with a distortion sensor to detect the changes of sucking ability and frequency of the infants. The data were transmitted via the wireless transmitter to a remote receiver, and the computing module of the intelligent pacifier would display the actual sucking force and frequency on the screen. Then, the caretakers could refer to the data and provide proper care for the infants.

The paper determines the optimal position of thermistors in sensitive components of gas pendulum omnibearing level posture sensor is d=900 μm (d is distance of two relatively detection thermistors). By using the finite element method, through the establishment of three-dimensional modeling of the thermistors of sensitive element in different positions, different tilting states, the distribution of temperature field and flow field inside the sensitive element are calculated. The results show that: (1) When the d is changed, the temperature field and flow field changes. (2) The relation curve, which is about the difference Δv of airflow velocity around the two relatively detection thermistors and tilt angle, changes with the d. This opens the effective approaches for the optimization design of the sensor.

The Internet of Things is a new type of technical system combining various types of information technology, the application of Internet of Things in agriculture meets the requirement of modern agriculture development and represents the orientation of future agriculture. In this article the Internet of Things system in agriculture is analyzed according to its systematic structure including its perception level, transmission level and application level and perception level, the sensor is the core of this level, multidimensional agricultural information can be obtained by advanced technology such as sensing and remote sensing about crops, soil and environment etc. The transmission level consists of wireless transmission network combing wireless transmission methods such as Zigbee, GPRS, WIFI and Bluetooth and network technology. The application level involves in intelligent management of agriculture including multi-dimensional information integration, intelligent decision and automatic control. The orientation of research and development is shown for the Internet of Things system in agriculture in this article. Its development will bring a brand-new reform for modern agriculture and realize agricultural automation and intellectualization.

In order to solve the environmental pollution caused by motor vehicle exhaust, this article designed and developed a miniaturized infrared exhaust gas sensor, can effectively detect the concentration of CO₂, CO, hydrocarbons, solves the existing sensor of large volume, slow response, etc.

Aiming at the problem of mixed gas detection in neural network and analysis on the principle of gas detection. Combining BP algorithm of genetic algorithm with hybrid gas sensors, a kind of quantitative analysis system of mixed gas is designed. The local minimum of network learning is the main reason which affects the precision of gas analysis. On the basis of the network study to improve the learning algorithms, the analyses and tests for CO, CO₂ and HC compounds were tested. The results showed that the above measures effectively improve and enhance the accuracy of the neural network for gas analysis.

It is necessary to choose reasonable sensor for the system of PHM. We can choose reasonable sensors based on environment of the system and the actual situation, at the same time, we must pay attention to choose the reasonable plan as a whole in order to make the system of sensor the best effect. The excellent system of sensor can obtain effective running status data, high precision. Otherwise, the system may cause a lot of invalid data, loss of critical data or reduce the data accuracy. Accordingly, the system of PHM is established on the basis of a wrong data that it couldn't achieve optimal results.