Diffraction of plane waves by a two-impedance wedge in cold plasma Ikiz, T.; Lyalinov, M.A.; Servest, A.H.
MMET Conference Proceedings. 1998 International Conference on Mathematical Methods in Electromagnetic Theory. MMET 98 (Cat. No.98EX114),
1998, Letnik:
2
Conference Proceeding
A wedge is an important conanical structure in diffraction theory. Practically a two-impedance wedge in a cold plasma may be used in modelling the electromagnetic scattering from a variety of large ...and complex objects. The solution is corrected in comparison with that obtained for the problem in question by Bobrovnikov and Fisanov (1988). In this study the scattered field is represented in the form of a Sommerfeld integral with an unknown spectral function. By using the impedance boundary conditions a nonhomogeneous functional equation is obtained. The solution of the functional equation can be represented in terms of /spl chi/-functions and S integrals. After determining the unknown spectral function in the Sommerfeld integral, the Sommerfeld contour is deformed into the steepest descent paths. During the deformation process the geometrical optics waves and the surface waves contributions are found. Diffraction coefficients are also discussed.
We study the problem of diffraction of an EM plane wave by an impedance wedge. In the general case of oblique incidence the problem was not solved explicitly, however, in some special cases of ...surface impedances the analytic solution has been obtained. The most natural way to obtain the practically important results for the diffraction coefficient in the general case of skew incidence is to apply the perturbation method. The problem can be solved for the normal incidence and for the grazing to the edge incidence. This enables us to develop the perturbation procedure for the following two cases: for very skew and almost normal incidences.
Plane wave diffraction by a resistive strip Veliev, E.I.; Kobayashi, K.; Ikiz, T. ...
MMET '96. VIth International Conference on Mathematical Methods in Electromagnetic Theory. Proceedings,
1996
Conference Proceeding
The analysis of the scattering by resistive strips is an important subject in diffraction theory. This geometry can be regarded as a suitable model of thin dielectric slabs and coating of finite ...length which are often used for radar cross section (RCS) reduction. In this paper, we shall analyze the plane wave diffraction by a resistive strip using the analytical-numerical approach which is entirely different from the previous methods employed to solve the impedance related problems. Applying the boundary condition to an integral representation of the scattered field, the problem is formulated as an integral equation satisfied by the unknown current density function. Expanding the current density function in terms of the Gegenbauer polynomials by taking into account the edge condition, our problem is reduced to the solution of an infinite system of linear algebraic equations (SLAE) satisfied by the unknown expansion coefficients.
One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for ...detection in shallow surveys at future apparitions. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 hours in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets). Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS. Most targets and recovered objects had apparent magnitudes centered around V~22.8 mag, with some becoming as faint as V~24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O-C residuals for our 1,854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22,000 positions of about 3,500 known minor planets and another 10,000 observations of about 1,500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields, increasing the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015.
Objectives. This study aimed to determine the relationship between musculoskeletal problems in office workers and their physical activity levels and quality of life. Methods. A questionnaire form, ...the quality of life scale (SF-36) and the international physical activity questionnaire (IPAQ) were used. Group differences were compared post hoc (Bonferroni) and non-parametrically (Mann-Whitney U test, etc.). Results. Among the participants, 81.7% experienced pain in at least one body area. Back pain was experienced most frequently at a rate of 54.8%, followed by neck and shoulder pain, respectively. According to the participants' physical activity levels, 58.5% (n = 141) were active, 37.3% (n = 90) were less active and 4.1% (n = 10) were very active. There was a significant relationship between the prevalence of musculoskeletal disorders (MSDs) among the participants and the participants' age, educational status, income status, regular exercise status, duration of computer use, eye complaints, complaints in the wrists and ergonomic chair use. Conclusion. The prevalence of MSDs was determined to be high in the office workers, while their levels of physical activity were found low. Training and exercises are needed to prevent MSDs in office workers and improve their levels of physical activity and quality of life.
Cochlear implants (CIs) improve spoken language skills as well as social and academic performance in children with severe and profound sensorineural hearing loss.
We compare the social skills, ...academic competence, and problem behaviors in children with CIs and their typical-hearing peers and investigate the relationship between language skills and social skills, academic competence, and problem behaviors in children with CIs.
Thirty-two children with CIs were divided into two groups according to implantation age: early (
= 17) and late-implanted group (
= 15). The control group was formed by the inclusion of five same-sex classmates of each implanted child selected by the teachers of the children with CIs. Thus, 160 typical-hearing children were included in the control group.
Thirty-two children with CIs and 160 typical-hearing children participated in this study.
Primary school teachers rated the children's social skills, academic competence, and problem behaviors using the Social Skills Rating System (SSRS). The language skills of the children with CIs were assessed with the Turkish Expressive and Receptive Language Test (TIFALDI).
A statistically significant difference was found between the SSRS scores of the study and control groups, which was mostly due to lower social skills, and academic competence, and higher problem behavior ratings in the late-implanted group. In the study group, there was a statistically significant correlation between TIFALDI and SSRS scores.
Early cochlear implantation provides advantages in social skills and vocabulary for children with profound congenital hearing loss. Late-implanted children need special support in different developmental areas despite attending mainstream education.
Hearing loss is associated with reduced quality and quantity of auditory input, and difficulty in cognitive and language skills. This study aimed to investigate the relationship between language, ...working memory, and rapid naming skills in children with mild to moderate sensorineural hearing loss (MMHL).
Twenty children with MMHL with the same auditory experience and demographical conditions using bilateral hearing aids were included. Verbal memory subscale of the Working Memory Scale (WMS), consisting of verbal short-term memory (V-STM) and verbal working memory (V-WM) subtests, was administered to all participants. They also completed rapid automatized naming tasks and standardized language measures.
The language score showed a moderate and significant correlation with verbal memory (VM) score (p = 0.03, r = 0.48) and a moderate and negative correlation with rapid automatized naming (RAN) duration (p = 0.06, r = −0.61). The VM score showed a moderate and significant negative correlation with RAN duration (p = 0.01, r = −0.67). The language level has a strong and significant positive correlation with V-STM (p = 0.007, r = 0.60), V-WM (p = 0.009, r = 0.58), and VM level (p = 0.003, r = 0.65). VM subtests levels have a strong and significant positive correlation with each other (p = 0.017, r = 0.53). RAN level has a strong and significant negative correlation with VM (p = 0.001, r = −0.70), V-WM (p = 0.001, r = −0.76), V-STM (p = 0.001, r = −0.69), and language level (p = 0.001, r = −0.77).
The results suggest that the language, verbal working memory, and rapid naming skills of children with MMHL are closely related. It is recommended that the relationship between verbal short-term memory, verbal working memory, rapid naming skills, and language skills should be considered in therapeutic and educational settings. To the best of our knowledge, this is the first study to examine the relationships between verbal-short-term -working memory, duration of rapid automatized naming, and language skills in children with MMHL.
Amaç –Dünyada her geçen gün turist sayısı artış göstermekte ve bu artışa bağlı olarak turizm destinasyonları arasındaki rekabet de hız kazanmaktadır. Destinasyonların rekabette üstünlük sağlamaları ...için rakipleri ile aralarındaki farkları ortaya çıkarmaları gerekmektedir. Destinasyon pazarlaması kapsamında gerçekleştirilen tanıtım, imaj, marka ve konumlandırma çalışmaları destinasyonların başarıyı sağlamasında anahtar rol oynamaktadır. Bu çalışmanın temel amacı, Kırıkkale ilinin destinasyon imajına yönelik olaraküniversite öğrencilerinin algısının belirlenmesidir. Yöntem –Araştırma nicel araştırma yöntemi, tarama modeli ve tekil tarama deseni ile gerçekleştirilmiştir. Araştırmanın çalışma evreni olarak Kırıkkale ili, örneklem olarak Kırıkkale Üniversitesi öğrencileri olarak belirlenmiştir. Araştırmada veri toplama tekniği olarak anket kullanılmıştır. Anket uygulaması sonucunda, 464 adet değerlendirilebilir anket formu elde edilmiştir. Anketlerden elde edilen verilerin analizinde t-testi ve tek yönlü varyans analizi (anova) kullanılmıştır.Bulgular –Araştırmadan elde edilen sonuçlar, Kırıkkale’nin genel olarak destinasyon imajının çok olumlu olmadığını göstermektedir. Şehrin genel özellikleri, tarih ve kültür, doğal çevre, turizm ve boş zaman faktörlerinin imajına yönelik algı görece daha olumsuzdur. Örneklemin büyük kısmının, Kırıkkale’nin beklentilerini karşılamadığı, bir daha gelmek istemediği ve Kırıkkale’yi çevresine tavsiye etmeyeceği bulgulanmıştır.Tartışma –Turizm sisteminin kompleks yapısı, destinasyon imajını hem gelişmiş hem de gelişmekte olan destinasyonların turizm politikası ve planlaması açısından en önemli destinasyon pazarlaması faktörlerinden biri haline getirmektedir. Kırıkkale’nin destinasyon imajının olumlu olmadığı, benzer çalışma ve destinasyonlarla karşılaştırıldığında da daha düşük seviyede olduğu anlaşılmaktadır. Kırıkkale gibi deniz-kum-güneş gibi olanaklarını bulunmayan destinasyonların “imaj” çalışmalarına bütüncül olarak yaklaşmaları gerekmektedir.
Purpose –The number of tourists in the world is increasing day by day and the competition among tourism destinations is gaining momentum in line with this increase. In order for destinations to gain competitive advantage, they need to reveal the differences between them and their competitors. Promotion, image, brand and positioning activities carried out within the scope of destination marketing play a key role in ensuring the success of destinations. The main purpose of this study is to determine the perception of university students regarding the destination image of Kırıkkale province.Design/methodology/approach –The research was conducted with quantitative research method, survey model and single survey design. Kırıkkale province was determined as the study population and Kırıkkale University students as the sample. A questionnaire was used as a data collection technique. As a result of the questionnaire application, 464 evaluable questionnaire forms were obtained. In the analysis of the data obtained from the questionnaires, t-test and one-way analysis of variance (anova) were used.Findings –The results obtained from the research show that the overall destination image of Kırıkkale is not very positive. The perception towards the image of the general characteristics of the city, history and culture, natural environment, tourism and leisure factors is relatively more negative. It was found that the majority of the sample did not meet their expectations, did not want to come to Kırıkkale again and would not recommend Kırıkkale to others.Discussion –The complex nature of the tourism system makes destination image one of the most important destination marketing factors for tourism policy and planning in both developed and developing destinations. It is understood that the destination image of Kırıkkaleis not positive and is at a lower level when compared with similar studies and destinations. Destinations like Kırıkkale, which do not have sea-sand-sun opportunities, should approach "image" studies holistically.
School counsellors often encounter ethically challenging situations due to contradictory values and roles. This qualitative research aimed to define school counsellors' ethical dilemmas and their ...responses to such situations. Twenty-seven school counsellors in Turkey were asked to respond to 13 vignettes with ethical dilemmas. The most frequent ethical dilemmas involved the limits of confidentiality, confusion about counsellors' professional roles in school settings, uncooperative behaviours among stakeholders, and suspected child sexual abuse. It was revealed that counsellors prioritise the students' benefit and respect students' privacy. They follow legal guidelines in risky situations and insist on working within their areas of competence; they are not willing to accept noncounselling tasks. The results and implications for counsellors, counsellor educators and researchers are discussed.
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