The g-modes of white dwarfs

The neutral g-modes of a degenerate fluid at zero temperature are analyzed. The g-modes of a degenerate fluid at finite but small temperatures are then expanded in terms of those of the zero temperature fluid. For nonrelativistic degenerate fluids it is found that (1) the g-eigenvalues are proportional to T mu(6)sub e mu(-1)sub i, where T is the internal temperature of the fluid, mu sub e and mu sub i are the mean molecular weights of electrons and ions, respectively; (2) the ion pressure is solely responsible for driving the g-modes. For white dwarfs of about a solar mass, the periods of the g-oscillations are in the range of a few hundredths of seconds

Nonlinear Dimensionality Reduction by Manifold Unfolding

Every second, an enormous volume of data is being gathered from various sources and stored in huge data banks. Most of the time, monitoring a data source requires several parallel measurements, which form a high-dimensional sample vector. Due to the curse of dimensionality, applying machine learning methods, that is, studying and analyzing high-dimensional data, could be difficult. The essential task of dimensionality reduction is to faithfully represent a given set of high-dimensional data samples with a few variables. The goal of this thesis is to develop and propose new techniques for handling high-dimensional data, in order to address contemporary demand in machine learning applications. Most prominent nonlinear dimensionality reduction methods do not explicitly provide a way to handle out-of-samples. The starting point of this thesis is a nonlinear technique, called Embedding by Affine Transformations (EAT), which reduces the dimensionality of out-of-sample data as well. In this method, a convex optimization is solved for estimating a transformation between the high-dimensional input space and the low-dimensional embedding space. To the best of our knowledge, EAT is the only distance-preserving method for nonlinear dimensionality reduction capable of handling out-of-samples. The second method that we propose is TesseraMap. This method is a scalable extension of EAT. Conceptually, TesseraMap partitions the underlying manifold of data into a set of tesserae and then unfolds it by constructing a tessellation in a low-dimensional subspace of the embedding space. Crucially, the desired tessellation is obtained through solving a small semidefinite program; therefore, this method can efficiently handle tens of thousands of data points in a short time. The final outcome of this thesis is a novel method in dimensionality reduction called Isometric Patch Alignment (IPA). Intuitively speaking, IPA first considers a number of overlapping flat patches, which cover the underlying manifold of the high-dimensional input data. Then, IPA rearranges the patches and stitches the neighbors together on their overlapping parts. We prove that stitching two neighboring patches aligns them together; thereby, IPA unfolds the underlying manifold of data. Although this method and TesseraMap have similar approaches, IPA is more scalable; it embeds one million data points in only a few minutes. More importantly, unlike EAT and TesseraMap, which unfold the underlying manifold by stretching it, IPA constructs the unfolded manifold through patch alignment. We show this novel approach is advantageous in many cases. In addition, compared to the other well-known dimensionality reduction methods, IPA has several important characteristics; for example, it is noise tolerant, it handles non-uniform samples, and it can embed non-convex manifolds properly. In addition to these three dimensionality reduction methods, we propose a method for subspace clustering called Low-dimensional Localized Clustering (LDLC). In subspace clustering, data is partitioned into clusters, such that the points of each cluster lie close to a low-dimensional subspace. The unique property of LDLC is that it produces localized clusters on the underlying manifold of data. By conducting several experiments, we show this property is an asset in many machine learning tasks. This method can also be used for local dimensionality reduction. Moreover, LDLC is a suitable tool for forming the tesserae in TesseraMap, and also for creating the patches in IPA.1 yea

The barriers of accepting Virtual Reality in Healthcare by older generation

Acute pain causes great anxiety in patients and is a significant challenge for the NHS staff. Chronic pain is a burden to the UK economy and causes substantial disability. Pain management is predicted to increase within the aging population in the UK. At the moment Pharmaceutical pain management techniques are commonly used, which are not only costly, but also resulting in significant side effects. Virtual Reality is an acceptable complement with minimal side effect. However there have been resistance in using VR amongst elderly population. This study explores the existing attitude and challenges expressed by elderly population in using VR technology for pain management. The study followed an experimental design and the finding indicated that pre-existing knowledge and experience of pain and VR, alongside the perceived ease of use and perceived usefulness of the technology has an impact on elderly’s attitude and adoption of VR technology

THE EFFECT of SYNTAGMATIC AND PARADIGMATIC RELATIONSHIP ON LEARNING GRAMMAR AMONG IRANIAN PRE-INTERMEDIATE EFL LEARNERS

The purpose of the present study was to explore the effects of using syntagmatic and paradigmatic relationships on learning grammar among Iranian pre-intermediate EFL learners. To fulfill the objectives of the study a Homogeneity test (Oxford Quick Placement Test) was administered among 70 students at the pre-intermediate level of a private language Institute and finally 40 participants were selected. Then, they were randomly divided into two subgroups, namely control and experimental groups. Before starting the treatment, a validated teacher-made grammar test was administered to students as pre-test to assess the participants' knowledge of grammar at the beginning of the course. Then, the experimental group received the treatment, which was teaching grammar through using syntagmatic and paradigmatic relations while the control group was taught using traditional methods of teaching. After 20 sessions of treatment,the two groups were administered the same teacher-made grammar test as post-test. Data were analyzed by Paired and Independent Samples t-test. The findings showed that the experimental group significantly performed better than the control group. Generally, the experimental groups outperformed the control groups. The results suggest that syntagmatic and paradigmatic relations can be used in English classes to develop listening grammar ability among Iranian EFL learners

High Resolution/Wideband on-Chip Phase-Shifting

A new active LO phase shifter was introduced and implemented in a 2x2 wide band MIMO receiver. The chip was designed with STMicroelectronics 90nm technology. The main advantages of the proposed phase shifter over previous works included a wide band range, high resolution and small area. The phase shifter is based on the dependency of the inverter propagation delay on the load capacitance. Simply, by changing the load capacitance of an inverter, a different propagation delay is generated. A number of these controllable delay cells are cascaded to provide the required phase-shift. In order for the delay cells to reduce the required amount of phase-shifting the I&Q swap circuit is introduced. The I&Q swap circuitry reduces the phase-shifting by one fourth of the original range. The wide band phase shifter is suitable for multi-standard radios, since just one phase shifter is needed to support all standards. This capability of the phase shifter could potentially reduce the size of the die and simplify the design. The measurement shows that the phase shifter is able to provide 360˚ of phase-shifting at the output base band signal when the LO is varying from 1.5GHz to 6GHz. A wider range of the phase shifter is achievable by reducing the capacitance load and increasing the number of cascaded delay cells. The proposed phase shifter is capable of achieving a very high resolution. The resolution of the phase shifter is a function of the inverter current capability and the load capacitance. The measurements show the average resolution of the proposed phase shifter is about 1.32ps. Passive components usually take up a large area on the chip. A MOS capacitor is used as the load to reduce the area of the proposed phase shifter. A method is proposed to improve the phase shifter stability over the temperature and process variations. This method is based on the fact that the propagation delay of an inverter is inversely proportional to the power supply. Therefore, the phase shifters’ power supply must be varied to maintain a relatively constant phase shifter resolution over the temperature and process variations

The Effect of Discontinuities Characteristics on Coal Mine Stability and Sustainability: A Rock Fall Prediction Approach

Rock fall related accidents continue to occur in coal mines, although artificial support mechanisms have been used extensively [1]. Roof stability is primarily determined in many underground mines by a limited number of methods that often resort to subjective criteria. It is argued in this paper that stability conditions of mine roof strata, as a key factor in coal mines, must be determined by a survey which proactively investigates fundamental aspects. Failure of rock around the opening happens as a result of both high rock stress conditions and the presence of structural discontinuities. The properties of such discontinuities affect the engineering behavior of rock masses causing wedges or blocks to fall from the roof or slide out of the walls [2]. A practical rulebased approach to assess the risk of a roof fall is proposed in the paper. The method is based on the analysis of structural data and the geometry and stability of wedges in underground coal mines. In this regard, an accident causing a huge collapse in a coal mine leading to four fatalities is illustrated by way of a case study. A comprehensive investigation of the hanging wall has been gathered through a systematic collection of evidence. The investigation results are then analyzed, and an interpretation of the evidence gathered is provided. For this purpose, horizontal and vertical profiles are prepared by geophysical methods to define the falling zone and its boundaries. The collapse is then modeled by the use of sophisticated computer programs in order to identify the causes of the accident and hence recommend corrective actions to prevent or minimize reoccurrence probability of similar accidents. The corrective measures are placed into a rule-based framework for the benefit of the mine operators