Contemporary environmental issues of landfill leachate: assessment & remedies

Landfills are the primary option for waste disposal all over the world. Most of the landfill sites across the world are old and are not engineered to prevent contamination of the underlying soil and groundwater by the toxic leachate. The pollutants from landfill leachate have accumulative and detrimental effect on the ecology and food chains leading to carcinogenic effects, acute toxicity and genotoxicity among human beings. Management of this highly toxic leachate presents a challenging problem to the regulatory authorities who have set specific regulations regarding maximum limits of contaminants in treated leachate prior to disposal into the environment to ensure minimal environmental impact. There are different stages of leachate management such as monitoring of its formation and flow into the environment, identification of hazards associated with it and its treatment prior to disposal into the environment. This review focuses on: (i) leachate composition, (ii) Plume migration, (iii) Contaminant fate, (iv) Leachate plume monitoring techniques, (v) Risk assessment techniques, Hazard rating methods, mathematical modeling, and (vi) Recent innovations in leachate treatment technologies. However, due to seasonal fluctuations in leachate composition, flow rate and leachate volume, the management approaches cannot be stereotyped. Every scenario is unique and the strategy will vary accordingly. This paper lays out the choices for making an educated guess leading to the best management option.

Idealized Operation of Third-Harmonic-Peaking Class-Ef Power Amplifier with Extended Maximum Operating Frequency

A new variant of Class-EF power amplifier (PA), the so-called third-harmonic-peaking Class-EF, is presented. It inherits a soft-switching operation from the Class-E PA and a low peak switch voltage from the Class-F PA. More importantly, the new topology allows operations at higher frequencies and permits deployment of large transistors which is normally prohibited since they are always accompanied with high output capacitances. Using a simple transmission-line load network, the PA is synthesized to satisfy Class-EF impedances at fundamental frequency, third harmonic, and all even harmonics as well as to simultaneously provide an impedance matching to 50-Ω load.

Mineralogical Characteristics and Transformations during Long-Term Operation of a Zerovalent Iron Reactive Barrier

Design and operation of Fe⁰ permeable reactive barriers (PRBs) can be improved by understanding the long-term mineralogical transformations that occur within PRBs. Changes in mineral precipitates, cementation, and corrosion of Fe⁰ filings within an in situ pilot-scale PRB were examined after the first 30 months of operation and compared with results of a previous study of the PRB conducted 15 months earlier using X-ray diffraction and scanning electron microscopy employing energy dispersive X-ray and backscatter electron analyses. Iron (oxy)hydroxides, aragonite, and maghemite and/or magnetite occurred throughout the cores collected 30 mo after installation. Goethite, lepidocrocite, mackinawite, aragonite, calcite, and siderite were associated with oxidized and cemented areas, while green rusts were detected in more reduced zones. Basic differences from our last detailed investigation include (i) mackinawite crystallized from amorphous FeS, (ii) aragonite transformed into calcite, (iii) akaganeite transformed to goethite and lepidocrocite, (iv) iron (oxy)hydroxides and calcium and iron carbonate minerals increased, (v) cementation was greater in the more recent study, and (vi) oxidation, corrosion, and disintegration of Fe⁰ filings were greater, especially in cemented areas, in the more recent study. If the degree of corrosion and cementation that was observed from 15 to 30 mo after installation continues, certain portions of the PRB (i.e., up-gradient entrance of the ground water to the Fe⁰ section of the PRB) may last less than five more years, thus reducing the effectiveness of the PRB to mitigate contaminants.

The Impact of the Recent Economic Recession on the operation of the NEC Contract in Northern Ireland

In May 2006, the NEC contract was introduced as the preferred contract for Northern Ireland public sector works. This was subsequently followed by the 2007 economic crash and ensuing recession, which continues to affect the Northern Ireland Construction Industry, to a greater extent than the remainder of the United Kingdom (UK). However, use of the NEC contract has increased during this period, particularly in the public sector. There has been debate in the literature regarding the impact of the NEC contract on adversarial behaviour, but little consideration of the impact of external economic factors on the use of the NEC contract. Using a sequential mixed method approach, the study aims to fill this gap in knowledge, through examination of the impact the economic downturn has had on the operation of the NEC contract in Northern Ireland. Qualitative and quantitative findings show that the demands placed by the NEC contract, and the effects of the economic recession, have exerted opposing forces contract implementation, thus hindering its execution. The findings can lead to a deeper understanding, in the context of both industry and academia, of situations where a lack of resources may negatively impact the operation of the NEC contract.

On-line operation of an intelligent seismic detector

This study describes the on-line operation of a seismic detection system to act at the level of a seismic station providing similar role to that of a STA /LTA ratio-based detection algorithms. The intelligent detector is a Support Vector Machine (SVM), trained with data consisting of 2903 patterns extracted from records of the PVAQ station, one of the seismographic network's stations of the Institute of Meteorology of Portugal (IM). Records' spectral variations in time and characteristics were reflected in the SVM input patterns, as a set of values of power spectral density at selected frequencies. To ensure that all patterns of the sample data were within the range of variation of the training set, we used an algorithm to separate the universe of data by hyper-convex polyhedrons, determining in this manner a set of patterns that have a mandatory part of the training set. Additionally, an active learning strategy was conducted, by iteratively incorporating poorly classified cases in the training set. After having been trained, the proposed system was experimented in continuous operation for unseen (out of sample) data, and the SVM detector obtained 97.7% and 98.7% of sensitivity and selectivity, respectively. The same type of ANN presented 88.4 % and 99.4% of sensitivity and selectivity when applied to data of a different seismic station of IM. © 2013 Springer-Verlag Berlin Heidelberg.

Pointers on Design and Operation of Cattle Restrainer Systems

The article discusses the importance of design and the people who run handling systems.

Integrated internal PIFA for UMTS operation of clamshell mobile phones

novel design of at internal PIFA integrated with an RF-shielding metal case for application in a clamshell or fielder-tvpe mobile phone is presented. The integrated PIFA has a bent and tapered radiating arm in order to easily fit in the casing of the clamshell mobile phone as an internal antenna. The integrated PlEA can also provide a wide operating bandwidth fir UM7S (1920-2170 MHz) operation. In addition, for the clamshell mobile phone in either the talk or standby condition, only a small effect on the operating bandwidth of the integrated PIFA is obtained. The experimental results of the proposed design are presented

Growth, optical characterization, and laser operation of a stoichiometric crystal KYb(WO4)(2)

We present our recent achievements in the growing and optical characterization of KYb(WO4)2 (hereafter KYbW) crystals and demonstrate laser operation in this stoichiometric material. Single crystals of KYbW with optimal crystalline quality have been grown by the top-seeded-solution growth slow-cooling method. The optical anisotropy of this monoclinic crystal has been characterized, locating the tensor of the optical indicatrix and measuring the dispersion of the principal values of the refractive indices as well as the thermo-optic coefficients. Sellmeier equations have been constructed valid in the visible and near-IR spectral range. Raman scattering has been used to determine the phonon energies of KYbW and a simple physical model is applied for classification of the lattice vibration modes. Spectroscopic studies (absorption and emission measurements at room and low temperature) have been carried out in the spectral region near 1 µm characteristic for the ytterbium transition. Energy positions of the Stark sublevels of the ground and the excited state manifolds have been determined and the vibronic substructure has been identified. The intrinsic lifetime of the upper laser level has been measured taking care to suppress the effect of reabsorption and the intrinsic quantum efficiency has been estimated. Lasing has been demonstrated near 1074 nm with 41% slope efficiency at room temperature using a 0.5 mm thin plate of KYbW. This laser material holds great promise for diode pumped high-power lasers, thin disk and waveguide designs as well as for ultrashort (ps/fs) pulse laser systems.

Room-temperature continuous-wave operation of GaInNAs/GaAs quantum dot laser with GaAsN barrier grown by solid source molecular beam epitaxy

We present the results of GaInNAs/GaAs quantum dot structures with GaAsN barrier layers grown by solid source molecular beam epitaxy. Extension of the emission wavelength of GaInNAs quantum dots by ~170nm was observed in samples with GaAsN barriers in place of GaAs. However, optimization of the GaAsN barrier layer thickness is necessary to avoid degradation in luminescence intensity and structural property of the GaInNAs dots. Lasers with GaInNAs quantum dots as active layer were fabricated and room-temperature continuous-wave lasing was observed for the first time. Lasing occurs via the ground state at ~1.2μm, with threshold current density of 2.1kA/cm[superscript 2] and maximum output power of 16mW. These results are significantly better than previously reported values for this quantum-dot system.

Agricultural tenancies: implied surrender and regrant and the operation of the Agricultural Tenancies Act 1995

Agricultural tenancies arising after 1st September 1995 are mostly governed by the Agricultural Tenancies Act 1995. As such, tenants under this Act do not benefit from the degree of protection conferred on tenancies already in existence, which remain under the Agricultural Holdings Act 1986. Section 4 of the 1995 Act seeks to protect those tenancies which subsequently inadvertently undergo a surrender and regrant and which would otherwise lose the protection of the 1986 Act. This paper seeks to investigate, by relating recent case law and statute to the situation of agricultural tenancies, the occasions where surrender and regrant might occur and whether in such instances the protection of the 1986 Act will be lost.

Risk allocation in a public–private partnership: a case study of construction and operation of kindergartens in Kazakhstan

In Kazakhstan, a transitional nation in Central Asia, the development of public–private partnerships (PPPs) is at its early stage and increasingly of strategic importance. This case study investigates risk allocation in an ongoing project: the construction and operation of 11 kindergartens in the city of Karaganda in the concession form for 14 years. Drawing on a conceptual framework of effective risk allocation, the study identifies principal PPP risks, provides a critical assessment of how and in what way each partner bears a certain risk, highlights the reasons underpinning risk allocation decisions and delineates the lessons learned. The findings show that the government has effectively transferred most risks to the private sector partner, whilst both partners share the demand risk of childcare services and the project default risk. The strong elements of risk allocation include clear assignment of parties’ responsibilities, streamlined financing schemes and incentives to complete the main project phases on time. However, risk allocation has missed an opportunity to create incentives for service quality improvements and take advantage of economies of scale. The most controversial element of risk allocation, as the study finds, is a revenue stream that an operator is supposed to receive from the provision of services unrelated to childcare, as neither partner is able to mitigate this revenue risk. The article concludes that in the kindergartens’ PPP, the government has achieved almost complete transfer of risks to the private sector partner. However, the costs of transfer are extensive government financial outlays that seriously compromise the PPP value for money.