Essays on Forecasting Financial and Economic Time Series

PhDThis thesis comprises three main chapters focusing on a number of issues related to forecasting economic and nancial time series. Chapter 2 contains a detailed empirical study comparing forecast perfor- mance of a number of popular term structure models in predicting the UK yield curve. Several questions are addressed and investigated, such as whether macroeconomic information helps in forecasting yields and whether predict- ing performance of models change over time. We nd evidence of signi cant time-variation in forecast accuracy of competing models, particularly during the recent nancial crisis period. Chapter 3 explores density forecasts of the yield curve which, unlike the point forecasts, provide a full account of possible uncertainties surrounding the forecasts. We contribute by evaluating predictive performance of the recently developed stochastic-volatility arbitrage-free Nelson-Siegel models of Chris- tensen et al. (2010). The one-month-ahead predictive densities of the models appear to be inferior compared to those of their constant-volatility counter- parts. The advantage of modelling time-varying volatilities becomes evident only when forecasting interest rates at longer horizons. Chapter 3 deals with a more general problem of forecasting time series under structural change and long memory noise. Presence of long memory in the data is often easily confused with structural change. Wrongly account- ing for one when the other is present may lead to serious forecast failure. In our search for a forecast method that can perform reliably in presence of both features we extend the recent work of Giraitis et al. (2013). A forecast strategy with data-dependent discounting is adopted and typical robust-to- structural-change methods such as rolling window regression, forecast averag- ing and exponentially weighted moving average methods are exploited. We provide detailed theoretical analyses of forecast optimality by considering cer- tain types of structural changes and various degrees of long range dependence in noise. An extensive Monte Carlo study and empirical application to many UK time series ensure usefulness of adaptive forecast methods

Free transportation and the related liability in United Arab Emirates

The transport of persons for a fare creates a contract that obliges a transporter to transport passengers to their agreed destinations safely. Where a passenger suffers harm during transportation, the transporter would be assumed to have breached this obligation. Therefore, it would be contractually liable to compensate that passenger, unless intervention by an external cause is proven. This article dwells on a different type of transportation. It examines cases where a passenger is transported without the payment of a fare to the transporter. The article focuses primarily on free transportation, as an example of such contracts, but also examines other cases such as secret transportation, curious transportation, driving school contracts and staying aboard a vehicle after the expiration of a transportation contract. The problem posed to both the law and the courts is whether these types of transportation also create contracts, the breach of which would render transporters contractually liable. This article seeks to determine the type of liability faced by such transporters where passengers are harmed during transportation, or its disruption, including the timeframe for such liability. Based on the analysis of legal opinions, relevant legislation and case law, it can be surmised that, in these cases, the transporter may be subject to either tortious liability or presumed liability rules, and, very rarely, to contractual liability rules

Additive manufacturing of WC-Co cermets using composite powders

Cermets are defined as “Composite materials consisting of two constituents, one being either an oxide, carbide, boride, or similar inorganic compound, and the other a metallic binder”. Cermets based on tungsten carbide -cobalt (WC-Co), in both sintered and coatings forms, are extensively used in the fabrication of engineering components that require excellent wear resistance. The excellent wear properties of sintered cutting tools arise because WC-Co cermets give a compromise between toughness, provided by the metal matrix (Co), and the hardness of the ceramic (WC) phase. However, in overlay coatings, a reaction between WC and Co during deposition can degrade their wear performance from the ideal one of WC in a ductile Co matrix. Additive manufacturing (AM) technologies such as laser powder bed fusion (L-PBF) or laser direct energy deposition (DED-L) can provide significant design flexibility in the manufacture of cutting tools. However, there are significant challenges in processing WC-Co materials when melting of the Co binder phase is involved. The effect of process parameters needs to be fully understood and optimised to avoid cracks, pores, and excessive reaction between the WC and Co phases during manufacture. In the present study, a novel type of WCM-12 wt.% Co powder, prepared by a “satelliting” method, was employed in both L-PBF and DED-L studies; WCM represents the commercially available mixed carbide with the tradename Spherotene®. In addition, a commercially available plasma densified WC-Co feedstock with a smaller particle size and higher Co (17 wt.%) content was also examined in the L-PBF process. In this study and for the first time, it is now possible to produce applicable WC-Co feedstock for AM using the simple manually prepared satelliting method. In DED-L, single clads were fabricated. The results demonstrated stable depositions, uniform distribution of WCM particles in the matrix, good bonding with the substrate, and an almost full density matrix. These aspects can show the applicability of this feedstock to produce high quality coatings. To define an appropriate process map, two hypothesises were employed. The first one compromised between linear energy density and powder feed rate. The second one used effective energy density versus powder deposition density. The results showed that the second approach is more representative to the melt pool physics. Also, a high WCM dissolution increased the microhardness and wear resistance of the multitrack deposited coatings. In L-PBF, the processability of the satellited WCM-12 wt.% Co feedstock was investigated. Melting trials were undertaken to evaluate the consolidation behaviour of single tracks within a single layer. Also, the evolution of surface morphology of single layers and multilayers was studied. A continuous and relatively uniform single-track morphology was obtained. This has led to a relatively smooth single layer without cracks or matrix pores. However, increasing the numbers of layers increased cracks significantly. The plasma densified WC-17 wt.% Co powder was used in a different L-PBF machine of a relatively large laser spot size. Uniform cubic samples without distortions were fabricated in a process window. However, all samples revealed microcracks and open pores on the as-laser-scanned surfaces

Investigation of facilities for an m-learning environment

The paper projected to study the field of m-learning focusing on investigating the facilities required to initiate an m-learning environment. Facilities and regular practices of conventional learning and e-learning was considered to find the potential facilities for m-learning environment. We used Integrated Tertiary Educational Supply Chain Model framework that stands on conventional education and illustrates the combined form of education supply chain and research supply chain model. Two surveys were conducted to collect data from students and teachers of higher education. The responses from both of the surveys have been presented and later compared with the findings from our studies of the existing learning environments. The significance of this research is in identifying the facilities for a learner and educator centric m-learning environment

Talent Management: Three new Perceptions intended for managing and retaining Talent in Bangladesh

This study aims at investigating the methods, importance, process, and present situation of managing talented employees in Corporations. The study revealed that having talented employees helps organizations to drive and be competitive but it is difficult to acquire such people. Thus, some innovative campaigns, for instance, global trainee and management cycle star programs have been created to motivate talented graduates to join the companies and to motivate existing talented employees to being more dedicated and engaged. In the recruitment of new employees, personality and interpersonal skills were more important than educational background because candidates were deemed to be proficient in specific areas, so, what a candidate must have is a personality matching the company’s culture especially the characteristic of working as a good team member. In this study, we suggested some important steps and methods that can be applied in the organizations which are totally running and managing by the HR Department. Moreover, these methods and steps can become successful by managing low rate of star turnover which is quite sensitive case now a day

An End-to-End Authentication Mechanism for Wireless Body Area Networks

Wireless Body Area Network (WBAN) ensures high-quality healthcare services by endowing distant and continual monitoring of patients' health conditions. The security and privacy of the sensitive health-related data transmitted through the WBAN should be preserved to maximize its benefits. In this regard, user authentication is one of the primary mechanisms to protect health data that verifies the identities of entities involved in the communication process. Since WBAN carries crucial health data, every entity engaged in the data transfer process must be authenticated. In literature, an end-to-end user authentication mechanism covering each communicating party is absent. Besides, most of the existing user authentication mechanisms are designed assuming that the patient's mobile phone is trusted. In reality, a patient's mobile phone can be stolen or comprised by malware and thus behaves maliciously. Our work addresses these drawbacks and proposes an end-to-end user authentication and session key agreement scheme between sensor nodes and medical experts in a scenario where the patient's mobile phone is semi-trusted. We present a formal security analysis using BAN logic. Besides, we also provide an informal security analysis of the proposed scheme. Both studies indicate that our method is robust against well-known security attacks. In addition, our scheme achieves comparable computation and communication costs concerning the related existing works. The simulation shows that our method preserves satisfactory network performance

Stakeholder Perspectives on Clinical Decision Support Tools to Inform Clinical Artificial Intelligence Implementation: Protocol for a Framework Synthesis for Qualitative Evidence

BACKGROUND: Quantitative systematic reviews have identified clinical artificial intelligence (AI)-enabled tools with adequate performance for real-world implementation. To our knowledge, no published report or protocol synthesizes the full breadth of stakeholder perspectives. The absence of such a rigorous foundation perpetuates the "AI chasm," which continues to delay patient benefit. OBJECTIVE: The aim of this research is to synthesize stakeholder perspectives of computerized clinical decision support tools in any health care setting. Synthesized findings will inform future research and the implementation of AI into health care services. METHODS: The search strategy will use MEDLINE (Ovid), Scopus, CINAHL (EBSCO), ACM Digital Library, and Science Citation Index (Web of Science). Following deduplication, title, abstract, and full text screening will be performed by 2 independent reviewers with a third topic expert arbitrating. The quality of included studies will be appraised to support interpretation. Best-fit framework synthesis will be performed, with line-by-line coding completed by 2 independent reviewers. Where appropriate, these findings will be assigned to 1 of 22 a priori themes defined by the Nonadoption, Abandonment, Scale-up, Spread, and Sustainability framework. New domains will be inductively generated for outlying findings. The placement of findings within themes will be reviewed iteratively by a study advisory group including patient and lay representatives. RESULTS: Study registration was obtained from PROSPERO (CRD42021256005) in May 2021. Final searches were executed in April, and screening is ongoing at the time of writing. Full text data analysis is due to be completed in October 2021. We anticipate that the study will be submitted for open-access publication in late 2021. CONCLUSIONS: This paper describes the protocol for a qualitative evidence synthesis aiming to define barriers and facilitators to the implementation of computerized clinical decision support tools from all relevant stakeholders. The results of this study are intended to expedite the delivery of patient benefit from AI-enabled clinical tools. TRIAL REGISTRATION: PROSPERO CRD42021256005; https://tinyurl.com/r4x3thvp. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/33145

In vivo study of optical speckle decorrelation time across depths in the mouse brain

The strong optical scattering of biological tissue confounds our ability to focus light deeply into the brain beyond depths of a few hundred microns. This challenge can be potentially overcome by exploiting wavefront shaping techniques which allow light to be focused through or inside scattering media. However, these techniques require the scattering medium to be static, as changes in the arrangement of the scatterers between the wavefront recording and playback steps reduce the fidelity of the focus that is formed. Furthermore, as the thickness of the scattering medium increases, the influence of the dynamic nature becomes more severe due to the growing number of scattering events experienced by each photon. In this paper, by examining the scattering dynamics in the mouse brain in vivo via multispeckle diffusing wave spectroscopy (MSDWS) using a custom fiber probe that simulates a point-like source within the brain, we investigate the relationship between this decorrelation time and the depth of the point-like light source inside the living mouse brain at depths up to 3.2 mm

Experimental and Modeling Study of Abrasive Wear of Tungsten Carbide Drilling Bit in Wet and Dry Conditions

The results of theoretical and experimental investigations carried out to study the effect of load and relative sliding speed on the abrasive wear behavior in drilling bit teeth surfaces of an insert tungsten carbide bit have been presented. Experimentally, an apparatus for abrasive wear tests conducted on the modified ASTM-G65 was modified and fabricated to facilitate loading and measurement of wear rate for the sand/ steel wheel abrasion test, which involves two cases of contact; first is at dry sand and second is under wet condition. These tests have been carried under varied operating parameters of normal load and sliding speed. A theoretical model based upon the Archard equation has been developed for predicting wear simulation by using ANSYS12.1 program for dry and wet abrasive wear rates. The general trend for all the results of wet tests is that an increase in the applied load as well as wheel rotational speed produces an increase in wear rate, while at the dry tests the behavior shows an increase and fluctuating in wear rate due to the transition in wear mechanism. As compared to the dry tests, the volume losses in wet tests have much higher values, that is because the presence of water which causes high adhesion between sand particles and specimen surface as well as wear-corrosion interaction which accelerate the wear rates. The percentage errors between theoretical and experimental results are more stable with the wet than dry tests due to the stability in wear rates