Performance comparison of differential space-time signalling schemes for OFDM systems

Differential transmit diversity is an attractive alternative to its coherent counterpart, especially for multiple antenna systems where channel estimation is more difficult to attain compared to that of single antenna systems. In this paper we compare two different types of differential transmit diversity techniques for OFDM based transmissions. The first technique uses differential space-time block codes (DSTBC) from orthogonal designs and the second uses the differential cyclic delay diversity (DCDD). The results compare the bit error performance for several transmit antenna configurations. The results show that DCDD offers a very close performance to that of DSTBC, with the advantage of a simplified receiver structure

Photon signature analysis using template matching

We describe an approach to detect improvised explosive devices (IEDs) by using a template matching procedure. This approach relies on the signature due to backstreaming ? photons from various targets. In this work we have simulated cylindrical targets of aluminum, iron, copper, water and ammonium nitrate (nitrogen-rich fertilizer). We simulate 3.5 MeV source photons distributed on a plane inside a shielded area using Monte Carlo N-Particle (MCNP TM) code version 5 (V5). The 3.5 MeV source gamma rays yield 511 keV peaks due to pair production and scattered gamma rays. In this work, we simulate capture of those photons that backstream, after impinging on the target element, toward a NaI detector. The captured backstreamed photons are expected to produce a unique spectrum that will become part of a simple signal processing recognition system based on the template matching method. Different elements were simulated using different sets of random numbers in the Monte Carlo simulation. To date, the sum of absolute differences (SAD) method has been used to match the template. In the examples investigated, template matching was found to detect all elements correctly

Defending Against Firmware Cyber Attacks on Safety-Critical Systems

In the past, it was not possible to update the underlying software in many industrial control devices. Engineering teams had to ‘rip and replace’ obsolete components. However, the ability to make firmware updates has provided significant benefits to the companies who use Programmable Logic Controllers (PLCs), switches, gateways and bridges as well as an array of smart sensor/actuators. These updates include security patches when vulnerabilities are identified in existing devices; they can be distributed by physical media but are increasingly downloaded over Internet connections. These mechanisms pose a growing threat to the cyber security of safety-critical applications, which are illustrated by recent attacks on safety-related infrastructures across the Ukraine. Subsequent sections explain how malware can be distributed within firmware updates. Even when attackers cannot reverse engineer the code necessary to disguise their attack, they can undermine a device by forcing it into a constant upload cycle where the firmware installation never terminates. In this paper, we present means of mitigating the risks of firmware attack on safety-critical systems as part of wider initiatives to secure national critical infrastructures. Technical solutions, including firmware hashing, must be augmented by organizational measures to secure the supply chain within individual plants, across companies and throughout safety-related industries

Impedance control approach in robot's leg dragging velocity variations

One of the challenging areas in developing bio-inspired legged robot is dynamic control, especially in environment interaction. Impedance control is widely used by researchers for dynamic interaction, but the majority only focus on adapting uneven terrain structure. This idea may not be suitable for pick-and-place task robot that has different weight due to its body weight and payload as well as locomotion on flat terrain. Thus, this paper presents leg velocity control through impedance control approach with the aim to increase the energy of the legged robot especially during leg dragging based on force on contact. The results show that proposed controller is applicable since it increases the energy and velocity of leg motion due to increase in force on contact while maintaining the shape of the leg motion

Chemical constituents and lipoxygenase inhibitory activity of Piper stylosum Miq.

ABSTRACT. Chemical constituents and lipoxygenase inhibitory activity of the aerial part of Piper stylosum have been studied. Fractionation and purification of the extracts afforded five lignans, identified as yangambin (1), sesamin (2), syringaresinol (3), pinoresinol (4), and medioresinol (5), together with other constituents; 4-allyl resorcinol, β-sitosterol, β-sitostenone, taraxerol, vanilin, and vanilic acid. The structures of these compounds were established by analysis of their spectral data, as compared to that of reported compounds. The lipoxygenase inhibitory activity of the extracts and isolated lignans were also evaluated.               KEY WORDS: Piperaceae, Piper, Piper stylosum, Lignan, Lipoxygenase Bull. Chem. Soc. Ethiop. 2019, 33(3), 587-592.   DOI: https://dx.doi.org/10.4314/bcse.v33i3.1

A Framework for Tracing the Flavouring Information to Accelerate Halal Certification

Halal industry is a new sector in the manufacturing industry in Malaysia and is a fast-growing global business. In Malaysia, JAKIM is the body responsible in matters relating to approve the halal certification. However, the process of issuing the halal certificate is time consuming. Based on the delay in issuing the halal certificate, this study conducted a case study to examine issues in halal certification. The reasons for the delay in issuing halal certification is the constraints in determining halal status of flavouring due to the absence of halal certificate when auditors were processing the documentation for applying certification. In addition, the inconsistent use of terms among the food producers and the auditors makes it difficult to trace halal status of flavouring. The case study also found that there is no framework that can help to trace the halal status of flavouring ingredient systematically. Thus, the study contributes a framework for tracing flavouring information to accelerate halal certification

Prioritizing implementation factors of electronic document management system (EDMS) using topsis method: a case study in Iraqi government organizations

Taking into consideration a complexity of EDMS implementation process which involves a combination of technological, organizational and users factors, this study explores how EDMS implementation factors can be ranked through these dimensions. This paper begins with an examination of the literature on EDMS implementation studies where a conceptual framework has been derived. The study then adopts the TOPSIS method as the analytical tool that tackles the issue in prioritizing the most desirable factors influencing EDMS implementation project. From the results, the top management support, budgetary, strategic planning, staff training, awareness, resistance to change, IT implementation team, ICT infrastructure, security and privacy/trust, and collaboration are the top-ten important factors for Iraqi government organizations to implement EDMS applications. This paper draws on the research results for implications of IT managerial practice, and then suggests some empirical tactics in order to enhance in managing the EDMS implementation process in government

The use of AVHRR data to determine the concentration of visible and invisible tropospheric pollutants originating from a 1997 forest fire in Southeast Asia

A massive forest fire in Indonesia in 1997 affected the whole Asian region by producing a large smoke plume, with Malaysia bearing the brunt due to the wind direction and weather conditions and because of its proximity to the source. The five primary fire produced pollutants were carbon monoxide (CO), sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3) and particulate matter less than 10 mm (PM10). The first four of these are, of course, invisible to conventional satellite-flown multispectral scanners operating in the visible and near infrared regions of the electromagnetic spectrum. The fifth, PM10, is present in the haze and therefore makes an observable contribution to the signal received by the Advanced Very High Resolution Radiometer (AVHRR). The haze in AVHRR channels 1 and 2 data for the fires of September 1997 has been used to study the concentration of PM10 directly. It has also been used to study the concentration indirectly—as a tracer or surrogate—for the four remaining materials, the gases CO, SO2, NO2 and O3. Data from ground observations have been used to calibrate the results and the distributions of the fire pollutants over Peninsular Malaysia have been plotted

Experimental investigation on the effect of natural tropical weather on interfacial bonding performance of CFRP-concrete bonding system

The existing reinforced concrete structures may require rehabilitation and strengthening to overcome deficiencies due to defect and environmental deterioration. Fibre Reinforced Polymer (FRP)-concrete bonding systems can provide solution for the deficiencies, but the durability of the bonded joint needs to be investigated for reliable structural performance. In this research the interfacial bonding behaviour of CFRP-concrete system under tropical climate exposure is main interest. A 300 mm concrete prism was bonded with CFRP plate on its two sides and exposed for 3, 6, and 9 months to laboratory environment, continuous natural weather, and wet-dry exposure in 3.5% saltwater solution at room and 40 °C temperature. The prisms were subjected to tension and compression load under bonding test to measure the strain and determine stress distribution and shear stress transfer behaviour. The results of the bonding test showed that load transfer was fairly linear and uniform at lower load level and changed to non-linear and non- uniform at higher load level. The force transfers causes the shear stress distribution being shifted along the bonded length. The combination of climate effects may have provided better curing of the bonded joints, but longer duration of exposure may be required to weaken the bond strength. Nevertheless, CFRP-concrete bonding system was only minimally affected under the tropical climate and salt solution