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In the development of wireless sensor networks, power consumption is one of the bottlenecks for wide applications. In order to improve the energy efficiency of wireless sensor networks, a wakeup radio scheme is presented. The main transceiver that is responsible for data communication is in the sleep mode most of the time. An additional device called the wakeup radio receiver is a simplified receiver with much lower power consumption and data rate than the main transceiver. It is always on to monitor the channels continuously. It detects the wakeup packet, and sends the main transceiver a wakeup trigger upon successful detection of a wakeup packet. However, the detection of a wakeup packet is a challenging task. Since the wakeup radio receiver operates in the 2.4 GHz industrial, scientific, and medical band, a wakeup packet can be greatly interfered in such a noisy channel, which may lead to detection performance degradation. Therefore, a multi-carrier wakeup radio receiver is proposed as a solution to interference mitigation by making use of frequency diversity. But in practical implementations, the impairments from the multi-carrier wakeup receiver itself cannot be neglected. The receiver detection performance may degrade due to the non-idealities at the receiver. In this thesis, the detection performance of the multi-carrier wakeup radio receiver in the presence of channel noise, fading, co-channel interference, as well as non-idealities is explored.

The 5,464 km long Yellow River (Chinese: Huang He) is the second longest river of the Peoples Republic of China. Its source is in Qinghai-Tibet Plateau and empties after serving an agricultural population of over 126 million people in the Bohai Bay. The main characteristic of the Yellow River is the extremely high sediment load which causes the river bed to rise up to 10 cm per year and the river mouth to propagate into the shallow Bohai Bay with an average velocity of 2 km per year. The rising bed level results in a rising water level causing dike-breaches, occurring with an average return period of 10 years. After a dike-breach the Yellow River changes its course, and a new flow path is formed. The length of the new flow path to the Bohai Bay is shorter than the previous one. This causes a drop in the water level at the place of the dike-breach. The bed level upstream of the dike-breach follows the drop of the water level. Meanwhile the river path becomes longer by deposition at the river mouth. Aggradation takes place and the water level rises again until the next dikebreach occurs. In chapter 1 this process and the Yellow River characteristicsis are described. The periodic rise and fall of water- and bed level, initiated in the delta region, is propagating in upstream direction causing a time dependent bed level. The amplitude of this process reduces in upstream direction. The research objective is to determine a length scale of the river reach under influence of this periodic rise and fall. The time depending variation of the riverbed can be estimated by a quasi-steady one-dimensional mathematical model, which is derived of the basic equations of motion and continuity of water and sand in chapter 2. To solve this model a numerical approach is applied, which is discussed in chapter 4. Linearising this model leads to a hyperbolic differential equation. I f more symplifications are made - not only quasi-steady, but also quasi-uniform - a parabolic differential equation is obtained. In chapter 3 both differential equations are studied more closely with for several boundary conditions and several parameters. The advantage of the analytical solution is a quickly obtained first estimation of the behaviour of the time depending bed level of the lower reach of the Yellow River. Both numerical- and analytical studies result in an estimation of the length scale, expressed as a relaxation length, of the river reach under influence of the development in the Yellow River delta. The results show that the diffussion coefficient, determined by the sediment transport formula and the slope of the bed level, is of great influence on the relaxation length. The relaxation length increases in case of: - increasing diffusion coefficient - increasing period of the boundary condition - using a hyperbolic model instead of a parabolic model - using a numerical model instead of an analytical model In case the boundary condition consists of a sum of sine functions, representing for example a sudden drop of the water level, the time depending bed level transforms into a sine function with increasing distance from the boundary condition. This is the result of the different periods of the sine functions. The smaller the period, the sooner it is damped. The diffusion coefficient for the Yellow River is approximately 400 m2/s, which results in a relaxation length of approximately 200 km in case of a periodic boundary condition with a sudden drop in water level and a period of 10 year.

The optical torque wrench is a laser trapping technique that expands the capability of standard optical tweezers to torque manipulation and measurement, using the laser linear polarization to orient tailored microscopic birefringent particles. The ability to measure torque of the order of kBT (∼4 pN nm) is especially important in the study of biophysical systems at the molecular and cellular level. Quantitative torque measurements rely on an accurate calibration of the instrument. Here we describe and implement a set of calibration approaches for the optical torque wrench, including methods that have direct analogs in linear optical tweezers as well as introducing others that are specifically developed for the angular variables. We compare the different methods, analyze their differences, and make recommendations regarding their implementations.

A series of Ce3+ doped α-Sr2−2xCexNaxP2O7 phosphor compounds has been prepared using a high-temperature solid-state reaction technique. The luminescence properties under vacuum ultraviolet-UV and x-ray excitation were studied. Luminescence spectra reveal three UV-emitting peaks at about 310, 330, and 350 nm from which we conclude that Ce3+ occupies two distinct sites in α-Sr2P2O7. The influences of the doping concentration, the temperature, and the excitation wavelength on the luminescence of Ce3+ at the Ce(I) and Ce(II) sites together with the decay characteristics are discussed. The light yield under x-ray excitation is found to be around 10 000 photons/MeV.

Microencapsulated phase change materials (microPCMs) have been widely applied in solid matrix as thermal-storage or temperature-controlling functional composites. The thermal conductivity of these microPCMs/matrix composites is an important property need to be considered. In this study, a series of microPCMs have been fabricated using the in situ polymerization with various core/shell ratio and average diameter; the thermal conductivity of microPCMs/epoxy composites were investigated in details. The results show that the microPCMs have smooth surface and regular global shape with compact methanol–melamine–formaldehyde shell. The shell thickness does not greatly influence the phase change behaviors of PCM. Moreover, smaller microPCMs embedded in epoxy can improve the thermal transmission ability of composites. The effect of thermal conductivity of composites can be improved with higher volume fraction (10–30%) of microPCMs; and smaller size microPCMs with the same content of PCM may also enhance the thermal transmission area in matrix. Modeling analysis of relative thermal conductivity indicates that mixing higher thermal conductivity additive in PCM or matrix is an appropriate method to improve the thermal conductivity of microPCMs/matrix composites.

Hydrological changes of the Irtysh River were analyzed concerning the changes of annual runoff and its distribution features within a year measured by coefficient of variation and concentration degree. Abrupt changes were detected by the heuristic segmentation method. Possible causes of the hydrological changes were investigated considering climate changes and human activities (especially the reservoir operation). The Mann-Kendall method was applied to estimate whether the temperature and precipitation was changed. The increased precipitation in winter may increase the runoff of April. The increased temperature and the decreased precipitation in the flood season may decrease the runoff. At the middle reaches, the impact of the reservoirs at the upper reaches is significant and may be the main factor leading to the abrupt decreases in annual runoff and its intra-annual variability and concentration. The increased water surface area of the reservoirs aggravates the evaporation and leads to annual runoff reduction. The reservoirs regulate runoff by storing water in the flood season and releasing water in the dry season. While at the lower reaches, the annual runoff remained steady and its intra-annual variation and concentration were reduced gradually because the impact of the reservoirs is relative small and the climatic impact may be more relevant.

In numerous radar applications, new problems concerning target detection in a clutter environment may occur. These problems cannot be solved using classical methods on the base of our current utilization of the reflection properties of various objects and their environment. Radar features that may assist in solving these problems are sought in Doppler-polarimetry. Doppler-polarimetric agile radar is able to transmit and receive simultaneously two orthogonal in-polarization signals with waveforms orthogonal in-time, providing the possibility for simultaneous measurements of all elements of the polarization backscattering matrix (BSM) and their Doppler characteristics. Such type of the radar has been developed at Delft University of Technology during this thesis project. Based on long-term Delft experience in linear frequency modulation (LFM) radar, this thesis gives major attention to LFM polarimetric agile radar. However, all major design and validation aspects presented are also useful for any other type of modulation (e.g. phase coded modulation and orthogonal frequency-division multiplexing), despite supplementary investigations on modulation-dependent system characteristics and performance may be needed. Actually two radar systems have been built up. One is in hardware to be used as an experimental research platform for acquiring polarimetric agile radar data, for supporting the verification of theoretical models and the development of signal processing algorithms using different waveforms. The other one is in software simulation environment to be used as a simulation platform not only for system-level evaluation of radar specs, but also for detailed radar design and analyses. Cross-validation of the whole radar system between simulations and measurements has been achieved. The presented design approach may benefit the whole life-cycle of each complex radar system, starting from the very beginning of the design phase up to the very end of the maintenance phase.

Background: Controlled restriction of cellular movement using microfluidics allows one to study individual cells to gain insight into aspects of their physiology and behaviour. For example, the use of micron-sized growth channels that confine individual Escherichia coli has yielded novel insights into cell growth and death. To extend this approach to other species of bacteria, many of whom have dimensions in the sub-micron range, or to a larger range of growth conditions, a readily-fabricated device containing sub-micron features is required. Results: Here we detail the fabrication of a versatile device with growth channels whose widths range from 0.3 μm to 0.8 μm. The device is fabricated using electron beam lithography, which provides excellent control over the shape and size of different growth channels and facilitates the rapid-prototyping of new designs. Features are successfully transferred first into silicon, and subsequently into the polydimethylsiloxane that forms the basis of the working microfluidic device. We demonstrate that the growth of sub-micron scale bacteria such as Lactococcus lactis or Escherichia coli cultured in minimal medium can be followed in such a device over several generations. Conclusions: We have presented a detailed protocol based on electron beam fabrication together with specific dry etching procedures for the fabrication of a microfluidic device suited to study submicron-sized bacteria. We have demonstrated that both Gram-positive and Gram-negative bacteria can be successfully loaded and imaged over a number of generations in this device. Similar devices could potentially be used to study other submicron-sized organisms under conditions in which the height and shape of the growth channels are crucial to the experimental design.

Heterogeneity is a general feature in biological system. In order to avoid possible misleading effects of ensemble averaging, and to ensure a correct understanding of the biological system, it is very important to look into individuals, such as a single bio-molecule or a single cell, for details. The size of a single bio-molecule/cell typically ranges from nanometer to micrometer scale. Therefore, the tools for study single-molecule/cell often consist of nano- and micro-features. The power of nanotechnology is such that it is possible to fabricate a wide variety of nano- and micro-scale structures and devices, which find more and more frequent application as powerful tools for biophysical studies of single-molecule/cell. This thesis reports several nano- and micro-fabricated structures that I, together with my colleagues, have developed for biophysical studies at single-molecule/cell level: (1) Nanofabricated zero-mode waveguides for single-molecule fluorescence experiments at biologically-relevant high concentrations; (2) Microfabricated mirrors for three-dimensional fluorescence imaging and tracking of single molecule / particle; (3) Microfabricated polydimethylsiloxane-based microfluidics device for studying submicron-scale bacteria (4) Microfabricated birefringent cylinders for use in optical torque wrench to study torsional properties of single biomolecules. Our main interest in zero-mode waveguide lies in its powerful potential to study single telomerase at work by visualizing individual incorporation of dye-labeled nucleotides. We have successfully developed several key fundamental elements towards single-molecule fluorescence studies of telomerase in ZMW: we have designed a biotin-labeled oligonucleotide specifically for human telomerase assay in ZMW - it can be immobilized on the ZMW floor via its biotin group, and it has the highest affinity for base-pairing with telomerase. We have also designed and acquired two types of special modified nucleotides for this assay: fluorescently phospholinked nucleotides (TMR--dATP and Atto532-dG6P), and we have demonstrated that both phospholinked nucleotides can be incorporated processively by human telomerase. We have constructed an optical setup specifically for single-molecule fluorescence studies in ZMWs. This setup can operates in two different modes, namely, massive parallel detection mode (using wide-field illumination and EMCCD detection), and high-speed single spot mode (using focused illumination spot and APD for high speed detection). We have successfully developed methods for nano-fabrication of ZMWs. We have also performed extensive characterizations on our ZMW devices using SEM (device geometric profiles), and FCS (detection volume, fluorophore working concentration). Our characterization results show that we are able to controlledly fabricate ZMWs with a suitable size (ca. 80nm in diameter) for single-molecule fluorescent studies at biologically relevant concentration (> 1μM), which is very important for meaningful studies of telomerase kinetics. Finally, we have demonstrated a method for successful surface treatment of ZMWs, by which the DNA substrates can be tethered specifically onto the glass floor of ZMWs, and more importantly, the non-specific transient adsorption of labeled nucleotides on ZMW surfaces has been reduced to a sufficient low level (one order of magnitude lower than the typical rate of nucleotide incorporation). Microfabricated mirror is one of the most promising tools for high-precision 3D imaging and particle tracking. We have developed a method based on electron beam lithography and wet etching of single-crystal silicon for the fabrication of V-groove micromirrors. 54.7°-symmetric V-groove micromirror was fabricated using regular (100) silicon wafer. To fabricate a mirror facet 45° relative to wafer surface, an off-axis cut silicon wafer (<100> off 9.7° to <110> ) was used. We have demonstrated that our V-groove micromirrors could be assembled into flow cell structures for imaging single fluorescent particles. We have also been developing a novel algorithm based on maximum likelihood estimation (MLE) for 3D tracking of single molecule/particle using micromirrors. Our simulation results demonstrated that our MLE tracking method outperformed center-of-mass tracking method as developed by Berglund et al. The ability to restrict the movement of cells in a controlled manner using microfluidics, allows one to study individual cells and gain added insight into aspects of their physiology and behaviour that can potentially be hidden in ensemble averaging experiments. We have developed a novel protocol based on electron beam lithography together with specific dry etching procedures for the fabrication of a microfluidic device suited to study submicron-sized bacteria. In comparison to approaches based on conventional optical lithography, our method provides greater versatility and control of the dimensions of the growth channels while satisfying the rapid-prototyping needs in a research environment. The widths of the submicron growth channels allow for the potential immobilization and study of different size bacteria with widths ranging from 0.3 μm to 0.8 μm. We verified by means of SEM that these structures are successfully transferred from Si into polydimethylsiloxane (PDMS) as well as from PDMS into PDMS. As a proof-of-principle, we demonstrated that the bacterium L. lactis can successfully be loaded and imaged over a number of generations in this device. Similar devices could potentially be used to study other submicron-sized organisms under conditions where the height and shape of the growth channels are crucial to the experimental design. The Optical Torque Wrench (OTW) is a special type of optical tweezers (OT) that uses birefringent dielectric particles, and has proved to be one of the most promising tools for torsional manipulation and torque measurement of single biomolecules. The main difference between OTW and conventional OT is that OTW uses a birefringent dielectric particle, which can be rotated by controlling the polarization of trapping laser, and therefore is able to apply and measure torque on the biomolecule attaching to the particle. We describe the use of electron beam lithography for the design, fabrication and functionalization of micron-scale birefringtent quartz cylinders. We demonstrate excellent control of the cylinders’ geometry, fabricating cylinders with heights of 0.5–2 μm and diameters of 200–500 nm with high precision while maintaining control of their side-wall angle. The flexible fabrication allows cylinders to be selectively shaped into conical structures or to include centered protrusions for the selective attachment of biomolecules. The latter is facilitated by straightforward functionalization targeted either to a cylinder’s face or to the centered protrusion alone. The fabricated quartz cylinders are characterized in an optical torque wrench, permitting correlation of their geometrical properties to measured torques. In addition, we tether individual DNA molecules to the functionalized cylinders and demonstrate the translation and rotational control required for single-molecule studies. By using micron-scale birefringent particles, OTW has the ability to measure torque of the order of kBT (~4 pN•nm), which is especially important in the study of biophysical systems at the molecular and cellular level. Quantitative torque measurements rely on an accurate calibration of the instrument. We have described and performed various methods of OTW calibration, some with direct OT analog and others developed specifically for the angular variables. Overall, the different methods lead to close results, which also agree with the theoretical prediction for the particle drag coefficient. However, the absolute values of the variables measured by the instrument should be expected to depend on the details of calibration method chosen. Motivated by the potential of the OTW to access the fast rotational dynamics of biological systems, a result of its all-optical manipulation and detection, we focus on the angular dynamics of the trapped birefringent particle, demonstrating its excitability in the vicinity of a critical point. This links the optical torque wrench to nonlinear dynamical systems such as neuronal and cardiovascular tissues, nonlinear optics and chemical reactions, all of which display an excitable binary (‘all-or-none’) response to input perturbations. On the basis of this dynamical feature, we devise and implement a conceptually new sensing technique capable of detecting single perturbation events with high signal-to-noise ratio and continuously adjustable sensitivity. Last but not least, we describe our efforts towards the study of single bacterial flagellar motor in OTW, which is one of our main interests in developing OTW technology. Bacterial flagellar motor is one of the most interesting and most complex molecular machines. Torque generation plays a crucial role in its functionality. Our progresses towards the study of torque generation in flagellar motor using OTW include: (1) A controlled functionalization of quartz cylinders has been developed for attaching a cylinder to a spinning flagellum, and importantly with the flagellum tethered to the cylinder’s center to avoid precession; (2) A theoretical framework has been developed to describe the rotational kinetics of a flagellum-tethered cylinder in the OTW. (3) A novel fabrication approach has been developed for nano-fabrication of birefringent particles using TiO2 rutile, which has a birefringence 32 times larger than quartz. This will enlarge the range of rotational frequency in which the flagellar motor can be studied in OTW; (4) A possible alternative construction of OTW based on circular polarized light for producing constant torque has been considered, and a method for calibration of such construction is also been discussed theoretically.