bluuebunny/crossref_metadata_2025 huggingface dataset:
“It Is Permitted to Marry a Kushite”
Authors: Goldenberg David M.
Published: May 2013

A strange statement appears in Maimonides' (d. 1204) code of Jewish law, theMishneh Torah. When dealing with prohibited marriages, Maimonides writes that a convert from among the gentiles, including the seven Canaanite nations (Deuteronomy 7:3), may marry within the Jewish community. Originally there were some exceptions to this in regard to four nations: Ammon, Moab, Egypt, and Edom. However, Sennacherib, King of Assyria, commingled all the nations, and since then these four nations have been mixed up with all the other permitted nations, and they have all become permitted. “Thus a convert these days, whether he be an Edomite, an Egyptian, an Ammonite, a Moabite, a Kushite, or any other nation, whether male or female, is permitted to enter the community [of Israel, i.e. to marry within the community] immediately.”
Can Secular Spirituality be Religiously Inspired? The Hasidic Legacy in the Eyes of Skeptics
Authors: Ross Nicham
Published: May 2013

A trenchant and rather paradoxical Hasidic saying asserts the following: He who believes the tall tales told by the Hasidim may be a fool, but he who does not believe them is a heretic. It turns out that many secular writers have in fact read and examined Hasidic tales sympathetically, without necessarily regarding them as true. But what exactly is the relationship of such non-believers to Hasidism? Can a secularist genuinely connect with texts that seem to be totally immersed in their religious context and driven by specifically religious interests? Can a reader who repudiates the assumptions of the original author (and even of his intended audience) nevertheless engage in a personally uplifting or even spiritually-inspired reading of such texts? Is there a spiritual dimension capable of traversing the barriers of religious doctrine, and penetrating the inner world of the heretic?
Hannah Arendt's Eichmann Controversy as Destabilizing Transatlantic Text
Authors: Sacks Adam J.
Published: May 2013

The controversy surrounding Hannah Arendt's reportage on the Eichmann trial in Jerusalem and the subsequent book cannot be underestimated. For Arendt personally, the trial was the decisive event in the second half of her life and amounted to nothing less than a second exile. On the world stage, it marked not only a critical turning point in international consciousness of the Holocaust, but also both initiated and reflected a critical shift in intra-Jewish representations and expression. Arendt's book could in fact be considered as a master text for Judaic studies in the second half of the twentieth century. To mention two of many possible consequences, the controversy may be seen as a pivot point from which the culture of the public intellectuals of New York argued itself out of the spotlight, as well as a primary catalyst for two of the most significant works on the Holocaust penned by women: Lucy Davidowicz'sThe War against the Jews(1975) and Leni Yahil'sThe Holocaust(1987).
משנים את מידות העולם: חוג הלומדים המהפכני בקלויז ברודי ומהפכת יחידות המידה בראשית העת החדשה
Authors: כהנא מעוז
Published: May 2013

בשנת 1668 נדפס בלונדון ספרו של המלומד האנגלי ג׳ון וילקינס (John Wilkins, 1614–1672) :‘An Essay towards a Real Character, and a Philosophical Language’. וילקינס היה כומר אנגליקני מתון, פילוסוף נטורלי, וגם ממיסדי ה‘Royal Society of London’ – החברה המלכותית שהיתה לאבן דרך בהתפתחות המדעית של אירופה. בספרו הציג וילקינס כמה מסרים רדיקליים. אחד מהם היה יצירתה של שפת כתיבה חדשה, אוניברסלית, שתחליף את הלטינית 1672–1614 ,הישנה של הכנסיה הקתולית, ותשמש מצע קשר למלומדים ומבקשי אמת מכל העולם. מגמה דומה התבטאה במשאלה נוספת, דמיונית לא פחות המלומד האנגלי ביקש להחיל על העולם כולו יחידת מדידת אורך אחת ויחידה, שתחושב באופן רציונאלי ובסולם עשרוני. מאז התפרקות האימפריה הרומית, לכל הפחות, היתה אירופה נתונה בתוהו ובוהו של מידות אורך משקל ונפח. בתוך יחידה מדינית אחת כצרפת או אנגליה יכלו לשמש בו זמנית במקביל מאות מידות שונות. יחידות מידה (שפעמים רבות נשאו שמות זהים) נשמרו במקומות שונים בצורות שונות לגמרי. קביעת יחידות המידה היתה לכלי שרת גם בידי שליטים מקומיים – אלה, כמובן, ביקשו לסמן בעזרתן את מרחב סמכותם, וגם אלה, כידוע, רבו מספור.
Optimal Fault Detection and Exclusion Applied in GNSS Positioning
Authors: Yang Ling , Knight Nathan L. , Li Yong , Rizos Chris
Published: May 2013

In Global Navigation Satellite System (GNSS) positioning, it is standard practice to apply the Fault Detection and Exclusion (FDE) procedure iteratively, in order to exclude all faulty measurements and then ensure reliable positioning results. Since it is often only necessary to consider a single fault in a Receiver Autonomous Integrity Monitoring (RAIM) procedure, it would be ideal if a fault could be correctly identified. Thus, fault detection does not need to be applied in an iterative sense. One way of evaluating whether fault detection needs to be reapplied is to determine the probability of a wrong exclusion. To date, however, limited progress has been made in evaluating such probabilities. In this paper the relationships between different parameters are analysed in terms of the probability of correct and incorrect identification. Using this knowledge, a practical strategy for incorporating the probability of a wrong exclusion into the FDE procedure is developed. The theoretical findings are then demonstrated using a GPS single point positioning example.
Functional analysis of bovine Nramp1 and production of transgenic cloned embryosin vitro
Authors: Cheng Xiang , Yu Xiaoli , Liu Yajun , Deng Jie , Ma Xiaoling , Wang Huayan
Published: May 2013

Natural resistance-associated macrophage protein 1 (Nramp1) plays an important role in restraining the growth of intracellular pathogens within macrophages. In this study,Nramp1cDNA was cloned from Qinchuan cattle and its anti-bacterial activity was demonstrated as being able to significantly inhibit the growth ofSalmonella abortusovisandBrucella abortusin macrophages. Calf fibroblasts stably transfected with pSP–NRAMP1–HA vector were used to reconstruct bovine embryos by somatic cell nuclear transfer (SCNT). Reconstructed embryos were maturatedin vitroand the blastocyst formation rate (14.0%) was similar to that of control embryos (14.5%). Transgenic blastocysts were transplanted into 43 recipient cattle, of which 14 recipients became pregnant as evidenced by non-return estrus and by rectal palpation. One fetus was aborted after 6½ months of pregnancy and transgene integration was confirmed by semi-quantitative polymerase chain reaction. Together, this study showed that bovine Nramp1 retains biological function against the growth of intracellular bacteria and can be used to reconstruct embryos and produceNramp1transgenic cattle, which may benefit the animal and enhance their ability to prevent attack by intracellular pathogens.
Viral endomyocardial infection in the 1st year post transplant is associated with persistent inflammation in children who have undergone cardiac transplant
Authors: Molina Kimberly , Denfield Susan , Fan Yuxin , Moulik Mousumi , Towbin Jeffrey , Dreyer William , Rossano Joseph
Published: May 2013

Background: Viral genome in cardiac allograft has been associated with early graft loss in children who have undergone cardiac transplant from unknown mechanisms. Methods: This study is a retrospective review of children who have undergone cardiac transplant at a single institution from 1/2004 to 5/2008. Patients underwent cardiac catheterisations with endomyocardial biopsies to evaluate for rejection – graded on Texas Heart Institute scale – and the presence of virus by polymerase chain reaction. Patients with virus identified during the first year post transplant were compared at 1 year post transplant with virus-free patients. Results: The cohort comprised 59 patients, and the median age at transplant was 5.1 years. Viral genomes were isolated from 18 (31%) patients. The PCR + group had increased inflammation on endomyocardial biopsies, with a median score of 4 (ISHLT IR) versus 1 (ISHLT 1R) in the PCR – group (p = 0.014). The PCR + group had a similar cardiac index (median 3.7 ml/min/m2), pulmonary capillary wedge pressure (median 10 mmHg), and pulmonary vascular resistance index (median 1.7 U m2) comparatively. PCR + patients were more likely to have experienced an episode of rejection (p = 0.004). Conclusions: Children who developed viral endomyocardial infections after a cardiac transplant have increased allograft inflammation compared with virus-free patients. However, the haemodynamic profile is similar between the groups. The ongoing subclinical inflammation may contribute to the early graft loss associated with these patients.
Evaluation of right ventricular function in patients with tetralogy of Fallot using the myocardial performance index and isovolumic acceleration: a comparison with cardiac magnetic resonance imaging
Authors: Koca Bülent , Öztunç Funda , Eroğlu Ayşe Güler , Gökalp Selman , Dursun Memduh , Yilmaz Ravza
Published: May 2013

Background: Assessment of right ventricular function is a key point in the follow-up of operated patients with tetralogy of Fallot. Cardiac magnetic resonance assessment of right ventricular function is considered the gold standard. However, this technique is expensive, has limited availability, and requires significant expertise to acquire and interpret the images. Myocardial performance index and isovolumic acceleration have recently been studied for the assessment of right ventricular function and are shown to be simple yet powerful tools for assessing patients with right ventricular dysfunction of various origins. Methods: In this study, the integrity of myocardial performance index and isovolumic acceleration obtained by tissue Doppler imaging echocardiography to quantify right ventricular function was assessed in 31 patients operated for tetralogy of Fallot. Myocardial performance index and isovolumic acceleration measurements were compared with the parameters derived by cardiac magnetic resonance imaging. Results: In this study, a significant correlation has not been detected between cardiac magnetic resonance-originated right ventricular ejection fraction, pulmonary regurgitation fraction and myocardial performance index, isovolumic acceleration obtained by tissue Doppler imaging echocardiography from the lateral tricuspid annulus of the right ventricle. Conclusion: We have concluded that when evaluated separately, myocardial performance index and isovolumic acceleration obtained from tissue Doppler imaging echocardiography can be used in the long-term follow-up of patients who have been operated for tetralogy of Fallot, but that they do not show correlation with cardiac magnetic resonance-originated right ventricle ejection fraction and pulmonary regurgitation fraction.
Adolescents’ ability to select healthy food using two different front-of-pack food labels: a cross-over study
Authors: Babio Nancy , Vicent Paloma , López Leonor , Benito Anna , Basulto Julio , Salas-Salvadó Jordi
Published: May 2013

Objective

To compare, in adolescents, two models of front-of-pack Guideline Daily Amounts (GDA) labels in terms of (i) friendliness and acceptance and (ii) the ability to choose a diet that closely follows the nutritional recommendations.

Design

A randomized cross-over study was designed to compare two simplified front-of-pack GDA nutrition labels.

Setting

A Spanish secondary school.

Subjects

Eighty-one healthy adolescents aged between 14 and 16 years were recruited. Participants were randomly exposed to two experimental non-real food-choice conditions using multiple-traffic-light or monochrome nutritional labels. Participants had to choose options from a closed menu for 5 d on the basis of the experimental front-of-pack labelling. For each meal, three food options with different nutritional compositions were given to the participants. The contents of total energy and fat, saturated fat, sugar and salt of the chosen options were calculated.

Results

There were no significant differences in baseline sociodemographic and anthropometric characteristics between participants regardless of the experimental condition in which they started. There were no carry-over effects between the experimental sequences. It was observed that when participants used the multiple-traffic-light GDA system they chose significantly less total energy (mean –123·1 (sd 211·0) kJ (−29·4 (sd 50·4) kcal), P < 0·001), sugar (−4·5 (sd 4·6) g, P < 0·001), fat (−2·1 (sd 4·5) g, P = 0·006), saturated fat (−1·0 (sd 1·9) g, P = 0·002) and salt (−0·4 (sd 0·5) g, P < 0·001) than when they used the monochrome GDA system.

Conclusions

Compared with the monochrome GDA front-of-pack nutritional label, the multiple-traffic-light system helped adolescents to differentiate between healthier and less healthy food, theoretically making it possible for them to choose a diet closer to dietary recommendations.
Underusage of radiotherapy and a lack of socio-economic disparity in treatment outcome: a population-based study on adenoid cystic carcinomas
Authors: Cheung Rex
Published: May 2013

This study used receiver operating characteristic curve to analyse a long list of biological, treatment and socio-economic predictors of adenoid cystic carcinoma treatment outcome. Anatomical staging was found to be the most predictive factor of outcome.

Purpose

This study used receiver operating characteristic curve (ROC) to analyse surveillance, epidemiology and end results (SEER) adenoid cystic carcinoma data to identify predictive models and potential disparity in outcome.

Materials and methods

For the risk modelling, each factor was fitted by a generalised linear model to predict the cause-specific survival. The area under the ROC was computed. Similar strata were combined to construct the most parsimonious models. A random sampling algorithm was used to estimate the modelling errors. Risk of adenoid cystic carcinoma death was computed for the predictors for comparison.

Results

There were 5,947 patients diagnosed from 1973 to 2009 included in this study. The mean follow-up time (SD) was 93·8 (90·6) months. Three out of five patients were women. The mean (SD) age was 58·55 (16·01) years. SEER stage was the most predictive factor of outcome (ROC area of 0·68). Sex, radiotherapy and surgery had ROC areas of about 0·57. None of the socio-economic disparities was found for treatment outcome. Radiotherapy was underused in localised and regional stages when the intent was curative, especially in older patients.

Conclusion

Anatomical staging was predictive and useful in treatment selection. Understaging and underuse of radiotherapy may have contributed to poor outcomes.
Metastatic small-cell lung carcinoma to the thyroid gland: a case report
Authors: Boimel Pamela , Turaka Aruna
Published: May 2013

Object

Metastasis to the thyroid gland is a rare event.

Methods

We describe an unusual case of a 38-year-old woman with a history of small-cell lung cancer (SCLC), presenting with a new nodule in the thyroid gland, found to be metastatic SCLC, without evidence of widespread dissemination.

Conclusions

A new thyroid nodule should be carefully evaluated for metastasis in a patient with a history of prior malignancy.
A qualitative study exploring the perceived impact of supervision training on cognitive therapy supervisor practice
Authors: Younge Joanne , Campbell Anne
Published: May 2013

Although cognitive therapy (CT) has a large empirical base, research is lacking for CT supervision and supervision training, which presents an obstacle for evidence-based practice. A pilot CT supervision training programme, based on Milne's evidence-based supervision and Roth & Pilling's supervision competences was developed by the Northern Ireland Centre for Trauma and Transformation (NICTT), an organization specializing in CT therapy provision and training. This pilot study qualitatively explores CT supervisors’ perceptions of the impact the training had on their practice. Semi-structured interviews were conducted with seven participants, transcribed verbatim and analysed using Burnard's thematic content analysis. Findings illustrated that experienced CT supervisors perceived benefit from training and that the majority of supervisors had implemented contracts, used specific supervision models and paid more attention to supervisee learning as a result of the training. Obstacles to evaluating supervision included the lack of reliable user-friendly evaluation tools and supervisor consultancy structures. Recommendations are also made for future research to establish the long-term effects of supervision training and its effect on patient outcomes. Implications for future training based on adult learning principles are discussed.
Participant Sexual Orientation Matters
Authors: Steffens Melanie C. , Landmann Sören , Mecklenbräuker Silvia
Published: May 2013

Research participants’ sexual orientation is not consistently taken into account in experimental psychological research. We argue that it should be in any research related to participant or target gender. Corroborating this argument, an example study is presented on the gender bias in face recognition, the finding that women correctly recognize more female than male faces. In contrast, findings with male participants have been inconclusive. An online experiment (N = 1,147) was carried out, on purpose over-sampling lesbian and gay participants. Findings demonstrate that the pro-female gender bias in face recognition is modified by male participants’ sexual orientation. Heterosexual women and lesbians as well as heterosexual men showed a pro-female gender bias in face recognition, whereas gay men showed a pro-male gender bias, consistent with the explanation that differences in face expertise develop congruent with interests. These results contribute to the growing evidence that participant sexual orientation can be used to distinguish between alternative theoretical explanations of given gender-correlated patterns of findings.
Auditory Distraction Eliminates Retrieval Induced Forgetting
Authors: Marsh John E. , Sörqvist Patrik , Beaman C. Philip , Jones Dylan M.
Published: May 2013

The Retrieval-Induced Forgetting (RIF) paradigm includes three phases: (a) study/encoding of category exemplars, (b) practicing retrieval of a sub-set of those category exemplars, and (c) recall of all exemplars. At the final recall phase, recall of items that belong to the same categories as those items that undergo retrieval practice, but that did not undergo retrieval practice themselves, is impaired. The received view is that this is because retrieval of target category-exemplars (e.g., “Tiger” in the category Four-legged animal) requires inhibition of nontarget category-exemplars (e.g., “Dog” and “Lion”) that compete for retrieval. Here, we used the RIF paradigm to investigate whether ignoring auditory items during the retrieval-practice phase modulates the inhibitory process. In two experiments, RIF was present when retrieval practice was conducted in quiet and when it was conducted in the presence of spoken words that were drawn from a different category to that from which the targets for retrieval practice were selected. In contrast, RIF was abolished when words that were either identical to, or merely semantically related to, the retrieval-practice words were presented as background speech. The results suggest that the act of ignoring speech can reduce inhibition of the non-practiced category-exemplars, thereby eliminating RIF, but only when the spoken words are competitors for retrieval (i.e., belong to the same semantic category as the to-be-retrieved items).
Mechanosensitivity and compositional dynamics of cell–matrix adhesions
Authors: Schiller Herbert B , Fässler Reinhard
Published: May 2013

Cells perceive information about the biochemical and biophysical properties of their tissue microenvironment through integrin‐mediated cell–matrix adhesions, which connect the cytoskeleton with the extracellular matrix and thereby allow cohesion and long‐range mechanical connections within tissues. The formation of cell–matrix adhesions and integrin signalling involves the dynamic recruitment and assembly of an inventory of proteins, collectively termed the ‘adhesome’, at the adhesive site. The recruitment of some adhesome proteins, most notably the Lin11‐, Isl1‐ and Mec3‐domain‐containing proteins, depends on mechanical tension generated by myosin II‐mediated contractile forces exerted on cell–matrix adhesions. When exposed to force, mechanosensitive adhesome proteins can change their conformation or expose cryptic‐binding sites leading to the recruitment of proteins, rearrangement of the cytoskeleton, reinforcement of the adhesive site and signal transduction. Biophysical methods and proteomics revealed force ranges within the adhesome and cytoskeleton, and also force‐dependent changes in adhesome composition. In this review, we provide an overview of the compositional dynamics of cell–matrix adhesions, discuss the most prevalent functional domains in adhesome proteins and review literature and concepts about mechanosensing mechanisms that operate at the adhesion site.
The balance of brains—corruption and migration
Authors: Ariu Andrea , Squicciarini Mara Pasquamaria
Published: May 2013

Corruption plays a significant role in how (un)attractive a country is to skilled workers. Rather than focusing on education or immigration policies, governments ought first to tackle corruption in the labour market if they want to attract international talent.
Homo artefaciens
Authors: Kováč Ladislav
Published: May 2013

Karl Popper's doctrine of empirical falsification has influenced many natural scientists, even though it denies the role of inductive reasoning. In reality, however, scientific progress can only come from objective measurements and the acknowledgement of the uncertainty of our models of the world.
Spectrum sensing and power efficiency trade‐off optimisation in cognitive radio networks over fading channels
Authors: Hassan Emad S.
Published: May 2013

Multiple secondary users can cooperate to increase the reliability of spectrum sensing in cognitive radio (CR) networks. However, the total transmission power grows approximately linearly with the number of cooperative secondary users. This study proposes a new approach to optimise the trade‐off between sensing reliability and power efficiency in cooperative CR networks over fading channels. The authors assume K cooperative secondary users each collect N samples during the sensing time. The proposed approach is based on dividing the spectrum sensing into two phases. In the first phase, the authors use only n1 of N samples (n1 ≤ N), to check the channels state, then k of K cooperative secondary users (k ≤ K), which are in deeply faded channels are discarded. The authors call this n1 a check point of the sensing time. The spectrum sensing with relatively less‐faded channels are continued during the second phase. Therefore there is a check point at which the sensing time can be optimised in order to maximise the probability of detection and the power efficiency. Several experiments are carried out to test the performance of the proposed approach in terms of probability of detection and power efficiency. The obtained results show that the proposed approach enhances the probability of detection and shortens the optimal sensing time. Moreover, it improves the overall power efficiency.
Vertical edge‐based mapping using range‐augmented omnidirectional vision sensor
Authors: Bacca Bladimir , Cufí Xavier , Salví Joaquim
Published: May 2013

Laser range finder and omnidirectional cameras are becoming a promising combination of sensors to extract rich environmental information. This information includes textured plane extraction, vanishing points, catadioptric projection of vertical and horizontal lines, or invariant image features. However, many indoor scenes do not have enough texture information to describe the environment. In these situations, vertical edges could be used instead. This study presents a sensor model that is able to extract three‐dimensional position of vertical edges from a range‐augmented omnidirectional vision sensor. Using the unified spherical model for central catadioptric sensors and the proposed sensor model, the vertical edges are locally projected, improving the data association for mapping and localisation. The proposed sensor model was tested using the FastSLAM algorithm to solve the simultaneous localisation and mapping problem in indoor environments. Real‐world qualitative and quantitative experiments are presented to validate the proposed approach using a Pioneer‐3DX mobile robot equipped with a URG‐04LX laser range finder and an omnidirectional camera with parabolic mirror.
Modelling and control of a springless resonant linear permanent magnet oscillomotor
Authors: Agarlita Sorin‐Cristian , Tutelea Lucian Nicolae , Boldea Ion
Published: May 2013

Several configurations of resonant linear permanent magnet (PM) oscillomotors have been proposed lately for different devices. Higher efficiency for competitive costs and weight, in comparison with rotary actuators containing rotary to linear transmission, can be secured by operation at resonance (mechanical eigenfrequency is equal to electrical frequency). This study proposes a closed‐loop position control system for a new, springless, resonant linear permanent magnet oscillomotor and demonstrates through digital simulations its capability to deliver precise and wide levels of output power under good efficiency conditions not only at a given (resonant) frequency, but for ±10% frequency range around it.
A novel rotor configuration for brushless doubly‐fed induction generators
Authors: Gorginpour Hamed , Jandaghi Behzad , Oraee Hashem
Published: May 2013

Brushless Doubly‐Fed Induction Generator has attractive features to be the first choice in next generation of wind generators. However, its efficiency and power‐to‐weight ratio are slightly lower in comparison to induction machine with the same rating. Considerable part of these imperfections arises from the rotor design, which produces magnetic field with considerable undesirable spatial harmonics. This paper proposes a novel rotor configuration to reduce spatial harmonic distortion of air‐gap magnetic field as well as improving some drawbacks of the conventional structure, including unequal magnitudes of rotor bar currents, teeth saturation at low average air gap magnetic fields, high core loss and inefficient magnetic material utilization. The rotor loops are connected in series in the new scheme rather than nested arrangement of the conventional design. Furthermore, the Imperialist Competitive Algorithm is used for optimising the conductor distributions in order to improve spatial distribution of the rotor magneto‐motive force. The rotor current is evaluated in each iterative step using electric equivalent circuit. The analytical procedure of determining the circuit parameters is modified for the case of series loops. Effectiveness of the novel configuration is verified by comparing the results of optimised and conventional designs in several experimental and simulation studies.
Direct current driving impedance matching method for rectenna using medical implant communication service band for wireless battery charging
Authors: Cheng Hui‐Wen , Yu Tsung‐Chi , Luo Ching‐Hsing
Published: May 2013

This study proposes a direct‐current (DC) driving impedance matching method for rectennas for the wireless charging of implantable lithium‐ion (Li‐ion) rechargeable batteries using the medical implant communication service band. Unlike the traditional method, which uses only the DC resistive load or battery potential, the proposed method adopts the output DC current of the dual‐diode rectifiers to establish a simple equivalent model for wireless battery charging. Using this model, the optimised impedance matching network of the rectenna is derived to maximise efficiency within the charging range of a Li‐ion battery. For 10 dBm input radio‐frequency (RF) power, the highest RF‐to‐DC conversion efficiency of the traditional matching method is 22.3%. For the proposed method, the RF‐to‐DC conversion efficiency is > 75% in the potential range of 3.7 to 4.2 V, which is the range used for over 90% of the charging duration. The best battery charging efficiency was 76.2% at a transmission distance of 50 cm.
VHF communication channel characterisations over complex wooded propagation paths with applications to ground wireless sensor networks
Authors: Sizov Vladimir , Gashinova Marina , Zakaria Nor , Cherniakov Mikhail
Published: May 2013

Results of measurement trials to estimate path loss and signal fading levels in very‐high frequency band are presented for a node‐to‐node ad‐hoc sensor network communication link with very low elevated antennas. Different typical landscapes were tested; from flat open areas to uneven woodland areas. Practical recommendations regarding utilisation of VHF band are formulated.
Miniaturisation of dual band monopole antennas loaded with screen printed cobalt nanoparticle ink
Authors: Sowpati Arun K. , Nelo Mikko , Palukuru Vamsi K. , Juuti Jari , Jantunen Heli
Published: May 2013

In this study, miniaturisation of dual band monopole antennas has been investigated with the screen printed magnetic thick films of cobalt nanoparticle ink. The resonant frequencies of antennas were tuned by printing of the ink with different layer thicknesses on top of the antenna elements. The influence of magnetic layers on resonance frequency, return loss, total efficiency and radiation pattern were measured and compared with a reference antenna without layers. For example, five layers of magnetic film (total thickness of 90 µm) on the monopole antenna tuned the frequency by 137 and 297 MHz in the lower (900 MHz) and upper frequency (1800 MHz) bands, respectively. The total efficiency of a magnetic film loaded monopole antenna in the upper frequency band was found to be increased marginally or remain unchanged. The radiation patterns of the antenna remained essentially unchanged, despite the presence and use of the magnetic thick films.
Developments in retrodirective array technology
Authors: Fusco Vincent , Buchanan Neil
Published: May 2013

There has been significant interest in retrodirective antennas, especially considering the wealth of applications that could be significantly enhanced, or created, by the use of such technology. There is enormous potential for retrodirective antennas where complicated automatic tracking systems would benefit from being replaced by much simpler systems. Retrodirective array technology offers one solution pathway since it can offer extremely fast tracking with relatively simple circuitry. Retrodirective or self‐steering arrays are suited for low radio frequency (RF) power mobile terminal use particularly on or between un‐stabilised vehicles. In this type of operational scenario, high degrees of relative movement are expected, and power consumption and weight of the antenna must be kept to a minimum. In this study, the authors give a brief historical review of basic retrodirective technology and elaborate on some recent developments at Queens University of Belfast associated with retrodirective antenna technology in relation to, two‐way communications, ultrafast RADAR, microwave imaging, spatial power transmission, mitigation of multipath effects and spatial encryption.
Dual‐band, dual‐circularly polarised antenna element
Authors: Dorsey William Mark , Zaghloul Amir I.
Published: May 2013

A dual‐band element that operates with dual‐circular polarisation in two separate industrial, scientific and medical bands is presented. The design that is based on concentric square slot/shorted‐ring configuration is realisable in cost‐effective printed circuit board technology making it attractive for low‐cost personal communications devices. The antenna element provides a flexible topology that allows for convenient, independent control of the polarisation and impedance bandwidth of two distinct frequency bands with no fundamental limitation on the ratio between the high‐ and low‐band frequency ranges. The topology of this element is presented, and the antenna concept is validated via simulated and measured results.
Torque ripple reduction technique with improved flux response for a direct torque control induction motor drive
Authors: Singh Bhoopendra , Jain Shailendra , Dwivedi Sanjeet
Published: May 2013

The availability of limited voltage vectors in a conventional direct torque control drive fed from a two‐level inverter causes torque and current ripples. In this study, a new torque ripple reduction technique with a modified look up table incorporating a larger number of synthesised non‐zero active voltage vectors is proposed to overcome the limitations of the conventional and duty ratio control switching strategies. The voltage vector selection criteria in the proposed technique are based to prevent the stator flux demagnetisation during the low‐speed operation with significant reduction in torque and current ripple. The proposed switching strategy is investigated through simulation and experimentally validated on a test drive.
Evaluations of current control in weak grid case for grid‐connected LCL‐filtered inverter
Authors: Xu Jinming , Xie Shaojun , Tang Ting
Published: May 2013

For grid‐connected inverters, switching harmonics can be effectively attenuated through an LCL‐type filter. In order to suppress resonance and guarantee good performance, many strategies (e.g. active damping (AD), harmonic resonant control, repetitive control and grid feedforward) have been proposed. However, the wide variation of grid impedance value challenges system stability in practical applications. The aforementioned methods need to be investigated. This study evaluates the applicability of each part of the overall control in a weak grid case with the use of a stability criterion. It has been demonstrated that the feedback‐based AD control can work well in a wide range of grid conditions. However, the resonant and repetitive control methods meet constraints. The grid feedforward method brings in an extra positive feedback path, and consequently results in high harmonics or even instability. Finally, a recommendation for system design has been presented. Simulations and experiments have been provided to verify the analysis.
Simple analytical approach to predict large‐signal stability region of a closed‐loop boost DC–DC converter
Authors: Liu Sucheng , Zhou Luowei , Lu Weiguo
Published: May 2013

A simple analytical approach to predict large‐signal stability region of switching power converters is presented. By the concept of input–output stability, the large‐signal stability region is estimated via the small‐signal feedback control loops. Therefore the influence of the small‐signal loop gains on the large‐signal stability region is also revealed. A Boost DC–DC converter with average‐current mode control is adopted as the example throughout the study to illustrate the derivation of the presented approach. The effectiveness of the approach is verified by both simulations and experimental results.
Generalised analytical methods and current‐energy control design for modular multilevel cascade converter
Authors: Wan Yun , Liu Steven , Jiang Jianguo
Published: May 2013

Modular multilevel cascade converter (MMCC) is a family of the emerging multilevel converters that are configured with a cascaded connection of full‐bridge submodules or half‐bridge ones by distinct topological structures. So far, MMCC family can be classified by basic configurations and submodule types into single‐star full‐bridge, double‐star half‐bridge (modular multilevel converter (MMC)), double‐star full‐bridge, double‐star half‐bridge back‐to‐back (indirect MMC), triple‐star full‐bridge (modular multilevel matrix converter, M3C), single‐delta full‐bridge and double‐delta full‐bridge (Hexverter). This study introduces a generalised and standard analytical procedure for MMCC and deals with the double‐star half‐bridge case (MMC) as example. A particular defined circulating current with a clearer physical meaning is used to analyse the complicated branch current composition and branch energy fluctuation. A full mathematical model based on state‐space equations is established for MMC and a corresponding energy‐current control strategy is presented. The validity of the control design and effectiveness of MMC is confirmed by simulation and experiment.
Low conduction loss and low device stress three‐level power factor correction rectifier
Authors: Su Bin , Zhang Junming , Wen Huiqing , Lu Zhengyu
Published: May 2013

A low conduction loss and low device stress three‐level rectifier is proposed and the corresponding neutral‐point voltage balance control scheme is presented in this study. Compared with the conventional rectifier, the MOSFET voltage rating can be reduced by half. The inductance and the volume of input inductor are reduced. The conduction losses can also be lowered because of the elimination of the front–end bridge rectifier and the adoption of synchronous rectification. The neutral‐point voltage balance algorithm based on the average current‐mode modulation is illustrated with constant frequency operation. To verify the theoretical analysis, a universal line input 100 kHz, 900 W prototype is built. The experimental results show that the input inductor volume is greatly reduced and the neutral‐point voltage balance of the prototype is fulfilled considering various load conditions and dynamic processes. The proposed rectifier improves the efficiency by 2% under 90 V line input voltage compared with the conventional one.
Implementing dynamic quick response with high‐frequency feedback control of the deformable constant on‐time control for Buck converter on‐chip
Authors: Chen Wen‐Wei , Chen Jiann‐Fuh , Liang Tsorng‐Juu , Huang Jian‐Rong , Wei Lu‐Chi , Ting Wei‐Yuan
Published: May 2013

In this study, implementing a dynamic quick response with high‐frequency feedback control (HFFC) of the deformable constant on‐time (COT) control for Buck converter on‐chip is proposed. The concept uses the HFFC to filter Vout at the load transient to change the on‐time width dynamically, preventing Vout from dropping markedly. Finally, 12 V input voltage, 3.3 V output voltage and 60 W output power with the HFFC are implemented to achieve a dynamic quick response for the integrated circuit of the proposed constant frequency COT for Buck converter. Experimental and SIMPLIS simulation results are compared to verify the viability and superiority of the proposed approach.
State‐space representation of DFIG‐based wind power plants
Authors: Díaz Guzmán , González‐Morán Cristina , Viescas Ceferino
Published: May 2013

This study shows a methodology for state‐space representation of large wind power plants, through models that include the dynamics of the internal grid. The methodology presented fundamentally separates plant and controls at the stage of formation of the model. It is shown then that most of the plant can be built up from elementary RL branches – with special clarification about the reduction of the induction machine to an RL network – that are put together by means of a incidence matrix. The problems and solutions of reference frame dynamics – complex because of the existence of two control frames for the doubly‐fed induction generator and different frames in the grid, one for each generator – are also discussed. The control is separately formulated into a gain matrix, and control and plant are put together by simple matrix algebra. As a result, detailed, large systems can be easily formed. The study shows an example in which ten generators are considered and shows that there may appear particular dynamic features when multi‐machine systems (rather than single, aggregated machine systems) are represented.
Power peaks against installed capacity in tidal stream energy
Authors: Sánchez Marcos , Iglesias Gregorio , Carballo Rodrigo , Fraguela Jose A.
Published: May 2013

Owing to the natural variability of tidal flow, the curve of available power against time at the site of a tidal stream plant is typically spiky. This means that, for the power peaks to be fully exploited, the installed capacity of the plant would have to be large relative to its mean power output. In practice, a balance should be struck between the percentage of the total resource that is exploited and the installed power (and installation cost) of the plant. The purpose of this study is to examine this problematic through a case study: a tidal stream plant proposed for Ria de Ortigueira, a large estuary in north‐west Spain with a tidal range of 4.5 m. A numerical model of the estuary hydrodynamics is implemented, calibrated and successfully validated using field data. The model is used to determine the tidal flow patterns. The question of the installed capacity is examined for the two areas with the greatest potential as tidal stream sites. It is shown that the nominal power that is required can be greatly reduced by relinquishing the peaks of the power curve, with only a slight reduction in the energy output.
Proportional resonant individual pitch control for mitigation of wind turbines loads
Authors: Zhang Yunqian , Chen Zhe , Cheng Ming
Published: May 2013

This study addresses the mitigation of wind turbine loads and fatigue such as blade bending moments, tilt and yaw moments etc. Currently, the wind turbine blades are normally controlled to turn collectively to limit the excess of wind power above rated wind speed conditions without any load attenuation. The individual pitch control (IPC) is a promising way to reduce the wind turbine loads. This study presents a proportional resonant (PR) IPC, which does not need the measurement of blade azimuth angle and multiple complex Coleman transformations between rotational coordinate frame and stationary coordinate frame. The new strategy can attenuate the 1p and higher harmonics on the wind turbine blades as well as 3p on the hub without any filters. The wind turbine code fatigue, aerodynamics, structures and turbulence is applied to a doubly fed induction generator‐based wind power generation system. The simulations are performed on the National Renewable Energy Laboratory 1.5 MW upwind reference wind turbine model. The simulation results are presented and discussed to demonstrate the capability and effectiveness of the proposed PR IPC method.
Thyristor‐based flexible ac transmission system for controlling the vanadium redox flow battery
Authors: Ontiveros Leonardo Javier , Mercado Pedro Enrique
Published: May 2013

The vanadium redox flow battery (VRB) is a large stationary energy storage system; which presents high‐speed response and overload capacity characteristics. The VRB produces a dc voltage between two terminals; so a power conditioning system composed principally by a dc/ac flexible ac transmission system (FACTS), is required in order to connect the battery to the power system. In this regard, this study proposes a new FACTS compensator for controlling the VRB based on a 12‐pulse thyristor converter with commutated capacitors on the ac side. This type of compensator offers a good transient response with low‐power converter losses. Simulations of the FACTS compensator employing Matlab/Simulink software validate the proposal and show the good performance of the proposed device.
Design, analysis and fabrication of a novel six‐axis micropositioning stage
Authors: Hu Ya‐Hui , Hwu Farn‐Shiun , Lin Kao‐Hui
Published: May 2013

The design and development of a novel six‐axis micropositioning stage are presented in this study. Based on Stewart's theory, negative Poisson's ratio is adopted for the design of flexure hinges for this stage. The stage consists of a top hexagonal plate, a bottom hexagonal plate and six trapezoidal amplifiers. The flexure hinge in the inner part of the amplifier has a symmetrical double layer, and that in the outer part of the amplifier has an unsymmetrical single layer. The deformation and amplification are calculated in a numerical simulation with the finite element method. An experiment for measuring the displacement of the stage is carried out. In the experiments, each amplifier is driven by a piezoelectric transducer, and the displacements are measured with a laser displacement sensor then recorded for comparison of the single‐axis amplifier with the six‐axis stage. The results show that the amplification of the displacement of a single‐axis amplifier is about 15. Also, the simulation and experimental results for the six‐axis stage show all errors of motion to be <3%. It is obvious that the novel six‐axis stage possesses the characteristics of high amplification and minimisation, as well as being low cost.
Experimental investigation of the effect of the design parameters of pressboard in mineral oil on creepage discharge propagation
Authors: Kim Yong‐Han , Seok Bok‐Yeol , Lee Young‐Jo , Koo Ja‐Yoon
Published: May 2013

One of the vital causes of the failure of oil transformers is considered as the creepage discharge propagation on pressboard. The authors performed an experimental investigation under an AC step test voltage to analyse the effects of the structure, distance and gluing direction of pressboard on creepage propagation. Flat, ribbed and grooved test specimens were prepared. Further, breakdown experiments were conducted for two gluing directions, parallel and vertical with respect to the electric field. For parallel gluing, the average breakdown voltage (VBD) of the ribbed and grooved types was 1.2–1.33 times that of the flat type. For vertical gluing, the VBD of the flat type was 1.28–1.66 times that of the same type with parallel gluing, whereas the values for the ribbed and grooved types were 1.02–1.11 times the corresponding values for parallel gluing. The rib height and groove depth do not seem to contribute greatly to the breakdown strength because most of the flashover propagation appeared not on the pressboard's surface but at the glued interface. The results of this preliminary investigation may be useful for improving the dielectric creepage strength of solid insulation systems using pressboard as radial spacers, and high‐voltage winding lead support parts.
Mesh optimisation methods for unstructured transmission‐line modelling
Authors: Sewell Phillip , Benson Trevor M. , Vukovic Ana , Cole Sam
Published: May 2013

Transmission‐line modelling (TLM) is a valuable technique for numerical simulation of electromagnetic fields. Recently, investigations have been successfully carried out into the use of the TLM approach on unstructured meshes However, as the local characteristics of mesh geometry will clearly make an impact upon the fidelity of simulations, it is necessary to examine suitable techniques for mesh optimisation. Three different methods have been investigated here to find optimal meshes for subsequent TLM simulations: the centroidal Voronoi Tessellation method, the optimal Delaunay triangulation method and a spring relaxation method. These different techniques are assessed in terms of maximum efficiency of the subsequent TLM simulations and the computational cost that is incurred to identify them. Several different canonical examples of mesh are considered to determine the generality of the conclusions drawn.