Sensing-Throughput Tradeoff for Interweave Cognitive Radio System: A Deployment-Centric Viewpoint

Secondary access to the licensed spectrum is viable only if interference is avoided at the primary system. In this regard, different paradigms have been conceptualized in the existing literature. Of these, Interweave Systems (ISs) that employ spectrum sensing have been widely investigated. Baseline models investigated in the literature characterize the performance of IS in terms of a sensing-throughput tradeoff, however, this characterization assumes the knowledge of the involved channels at the secondary transmitter, which is unavailable in practice. Motivated by this fact, we establish a novel approach that incorporates channel estimation in the system model, and consequently investigate the impact of imperfect channel estimation on the performance of the IS. More particularly, the variation induced in the detection probability affects the detector's performance at the secondary transmitter, which may result in severe interference at the primary users. In this view, we propose to employ average and outage constraints on the detection probability, in order to capture the performance of the IS. Our analysis reveals that with an appropriate choice of the estimation time determined by the proposed model, the degradation in performance of the IS can be effectively controlled, and subsequently the achievable secondary throughput can be significantly enhanced.Comment: 13 pages, 10 figures, Accepted to be published in IEEE Transactions on Wireless Communication

Crystal structure of the high-pressure phase of the oxonitridosilicate chloride Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃0.2

The structural compression mechanism of Ce4[Si4O3 + xN7 − x]Cl1 − xOx, x≃ 0.2, was investigated by in situ single-crystal synchrotron X-ray diffraction at pressures of 3.0, 8.5 and 8.6 GPa using the diamond–anvil cell technique. On increasing pressure the low-pressure cubic structure first undergoes only minor structural changes. Between 8.5 and 8.6 GPa a first-order phase transition occurs, accompanied by a change of the single-crystal colour from light orange to dark red. The main structural mechanisms, leading to a volume reduction of about 5% at the phase transition, are an increase in and a rearrangement of the Ce coordination, the loss of the Ce2, Ce3 split position, and a bending of some of the inter-polyhedral Si—N—Si angles in the arrangement of the corner-sharing Si tetrahedra. The latter is responsible for the short c axis of the orthorhombic high-pressure structure compared with the cell parameter of the cubic low-pressure structure

Compressibility of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4−xAlxOxN7−x] (x = 2; M = Sr, Ba)

The compressibilities of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4−xAlxOxN7−x] (x = 2; M = Sr, Ba) were investigated by in situ high-pressure X-ray powder diffraction. Pressures up to 42 GPa were generated using the diamond–anvil cell technique. The title compounds are structurally stable to the highest pressure obtained. A fit of a third-order Birch–Murnaghan equation-of-state to the p–V data results in V0 = 302.91 (6) Å3, B0 = 176 (2) GPa and B′ = 4.4 (2) for SrYb[Si4N7]; V0 = 310.4 (1) Å3, B0 = 161 (2) GPa and B′ = 4.6 (2) for SrYb[Si4−xAlxOxN7−x]; and V0 = 317.3 (5) Å3, B0 = 168 (2) GPa and B′ = 4.7 (2) for BaYb[Si4−xAlxOxN7−x]. While the linear compressibilities of the a and c axes of BaYb[Si4−xAlxOxN7−x] are very similar up to 30 GPa, distinct differences were observed for SrYb[Si4N7] and SrYb[Si4−xAlxOxN7−x], with the c axis being the most compressible axis. In all of the investigated compounds the bulk compressibility is dominated by the compression behaviour of the tetrahedral network, while the size of the substituted cation plays a minor role

Alkaline Dehydration of Human Urine Collected in Source-Separated Sanitation Systems Using Magnesium Oxide

Fresh human urine, after it is alkalized to prevent the enzymatic hydrolysis of urea, can be dehydrated to reduce its volume and to produce a solid fertilizer. In this study, we investigated the suitability of MgO to alkalize and dehydrate urine. We selected MgO due to its low solubility (90% and N recovery of 80%, and yielded products with high concentrations of macronutrients (7.8% N, 0.7% P and 3.9% K). By modeling the chemical speciation in urine, we also showed that ammonia stripping rather than urea hydrolysis limited the N recovery, since the urine used in our study was partially hydrolyzed. To maximize the recovery of N during alkaline urine dehydration using MgO, we recommend treating fresh/un-hydrolysed urine a temperature <40 degrees C, tailoring the drying substrate to capture NH4+ as struvite, and using co-substrates to limit the molecular diffusion of ammonia. Treating fresh urine by alkaline dehydration requires only 3.6 kg MgO cap(-1)y(-1) and a cost of US$ 1.1 cap(-1)y(-1). Therefore, the use of sparingly soluble alkaline compounds like MgO in urine-diverting sanitation systems holds much promise

The Co-Ni distribution in decagonal Al69.7(4)Co10.0(4)Ni20.3(4)

The Co—Ni distribution in d-Al69.7(4)Co10.0(4)Ni20.3(4) was investigated based on X-ray and neutron diffraction data. The structure was modelled in higher dimensional space using the ‘charge-flipping' and ‘low-density elimination' methods and it was quantitatively refined in three-dimensional space employing a pseudo-approximant approach. In higher-dimensional description, the Co atoms are found at the centre of one of the two symmetry independent occupation domains, enclosed by regions mainly occupied by Ni. The other occupation domain is mostly occupied by Al. In physical space Co atoms are located in the centres of small Al pentagons and form pentagonal units, which are arranged in decagonal rings. On these sites Co is partly substituted by Ni, while all other transition metal sites are occupied by Ni and to a minor degree by Al. The fraction of Co found on transition metal sites decreases with decreasing Co-Co distances, whereby Co is replaced by N

How IT Consumerization Affects the Stress Level at Work: A Public Sector Case Study

IT consumerization refers to the adoption of consumer technologies in an enterprise context and is becoming increasingly important in both research and practice. While there are often positive effects attributed with the trend, e.g. with respect to increased performance or motivation, not much attention has yet been given to the effects it has on stress of employees. In order to close this research gap, we conduct a qualitative single case study in the public sector. We derive four major stressors that are related to IT consumerization, i.e. 1) increased reachability, 2) lack of competence, 3) workflow changes, and 4) system redundancies. These stressors are discussed with respect to related theory concepts in IS. Moreover, they are used to derive recommendations for practitioners with respect to policy development and communication. Our paper contributes to the recent discussion on theoretical implications of IT consumerization effects

Аутсорсінгова модель реалізації корпоративної соціальної відповідальності

У статті обґрунтовано необхідність і визначено шляхи використання аутсорсінгу корпоративної соціальної відповідальності в соціальній політиці України. Основним аргументом на користь такого аутсорсінгу є надзвичайна складність (а відтак – і ресурсоємність) процесу управління програмами корпоративної соціальної відповідальності. Використання різних форм (насамперед, повної та часткової) аутсорсінгу корпоративної соціальної відповідальності має найбільшу перспективу на регіональному рівні здійснення соціальної політики – в структурі фондів розвитку громади.В статье обоснована необходимость и определены пути использования аутсорсинга корпоративной социальной ответственности в социальной политике Украины. Основным аргументом в пользу такого аутсорсинга служит чрезвычайная сложность (а значит – и ресурсоемкость) процесса управления программами корпоративной социальной ответственности. Использования разных форм (прежде всего, полной и частичной) аутсорсинга корпоративной социальной ответственности имеет наибольшую перспективу на региональном уровне осуществления социальной политики – в структуре фондов местного развития.The paper argues the necessity and defines means of application of outsourcing to corporate social responsibility (CSR) in social policy of Ukraine. As CSR (corporate charity) is a secondary (not-product-related) activity to any for-profit organization, the allocation of recourses (human, managerial, financial etc.) to this activity may decrease effectiveness of the major (productrelated) functions, lessening the competitive ability of an enterprise. Initiation of specialized CSR-departments within an organizational structure (in order to provide expenditure control, feedback control and social effect monitoring) is a luxury, which most businesses in Ukraine can not afford. CSR-ignoring practices contradict imperatives of conventional modern business rules (e.g. sustainable development doctrine), which have presented CSR as a “must” for prosperous firms and successful for-profits throughout the world. Ukraine is also involved in the deployment of those imperatives as a new market economy country. Taking the burden of CSR-caused extra costs off a firm, outcontracting of CSR may contribute to wide spreading of corporate philanthropy, thus providing social policy and social-oriented activities in Ukraine with potentially essential assets. The paper derives, that deployment of CSR-outsourcing will produce the best effect on the regional level of social policy of Ukraine – within community foundations as community-based non-profit organizations, usually established in an area to help solving local social problems through accumulation and distribution chiefly local resources, aimed for social projects and programs of different kind