895 research outputs found
Astrophysical probes of dark matter: opportunities and challenges from a strong gravitational lensing perspective
PERANCANGAN DAN IMPLEMENTASI PATCH ANTENNA MIKROSTRIP SEGITIGA MENGGUNAKAN DIELEKTRIK UDARA PADA FREKUENSI 3400 MHz – 3600 MHz Design and Implementation of Triangular Microstrip Patch Antenna Using The Dielectric of Air on Frequency 3400 MHz – 3600 MHz
ABSTRAKSI: Antena mikrostrip banyak dikembangkan karena massanya yang ringan dan dapat menyesuaikan bentuk dengan tempat diletakkan. Metode pencatuan pada antena ini dapat dibedakan menjadi tiga, yaitu pencatuan mikrostrip, pencatuan probe, dan pencatuan EMC (electromagnetically coupled). Metode EMC pertama kali dikemukakan oleh K.F Lee, yang dirancang untuk menghasilkan bandwidth yang lebar.Pada Tugas Akhir ini, dirancang dan disimulasikan antena mikrostrip pada rentang frekuensi 3400 MHz – 3600 MHz untuk mendukung teknologi WiMAX, dengan menggunakan software Ansoft HFSS 9.2. Metode pencatuan yang digunakan adalah EMC yang menggunakan dielektrik udara pada struktur pencatuan L-strip, dengan bentuk patch segitiga. Pada simulasi, dilakukan pengulangan ukuran dimensi antena untuk mendapatkan hasil yang sesuai dengan spesifikasi rancangan antena, yaitu dengan mengubah ukuran patch, groundplane, feeder, serta tinggi air gap. Hasil simulasi yang diperoleh, diimplementasikan dengan menggunakan bahan, yaitu tembaga dengan ketebalan 1 mm.Hasil pengukuran yang didapatkan untuk frekuensi 3400 MHz – 3600 MHz adalah VSWR �� 1.25. Sedangkan untuk VSWR �� 2, dihasilkan bandwidth yang sangat lebar yaitu 1122 MHz pada rentang frekuensi 2878 MHz – 4000 MHz. Untuk pola radiasi antena yang terukur adalah unidireksional, serta polarisasinya berbentuk elips. Gain yang mampu dicapai antena ini adalah sekitar 6.31 dBi.Kata Kunci : Antena mikrostrip, Metode EMC, WiMAX, patch, groundplane, feeder, serta tinggi air gap.ABSTRACT: Many microstrip antennas are developed because of light in weight and adjusting a shape of placing. The feeding method of these antennas are divided into three types, which are microstrip feeding, probe feeding, and EMC (electromagnetically coupled) feeding. The EMC method is recognized at the first time by K.F Lee and designed for producing a wide bandwidth.At this Final Project, the microstrip antenna is designed and simulated at range frequency 3400 MHz – 3600 MHz for supporting WiMAX technology with using Ansoft HFSS 9.2 software. The used feeding method is EMC with the dielectric of air at the feeding structure of L-strip and triangular patch. In the simulation, the repetition of size of the antenna dimensions, which are patch, groundplane, feeder, and also a height of air gap, is done for getting a suitable result to the specification of antenna design. The result of simulation is implemented with using a material, which is a copper with a thickness 1 mm.The result of measurement, which is obtained for frequency 3400 MHz – 3600 MHz, is VSWR �� 1.25. At the value of VSWR �� 2, it results a very wide bandwidth, which is 1122 MHz at range frequency 2878 MHz – 4000 MHz. The measured radiation pattern of antenna is unidirectional, and also its polarization is ellipse. The obtained gain of this microstrip antenna is around 6.31 dBi.Keyword: microstrip antennas, The EMC method, WiMAX, patch, groundplane, feederand also a height of air gap,
The Impact of the Bologna Reform on Student Outcomes
How did the introduction of the Bachelor-degree system affect students in Ger-
many? Combining rich data on university students with administrative data
on universities' study programs, we exploit variation in the timing of Bachelor-
degree implementation across departments. To account for endogeneity in stu-
dents' enrollment decisions, we apply an instrumental-variable approach based
on the distance differential between an individual's nearest universities with a
Bachelor's and a traditional degree program. Overall, we do not find reform ef-
fects on students' mobility, drop out, and internship participation, although there
is indication that the reform reduced drop out for females and for high-achieving
students and increased study satisfaction
The influence of Wasta on employees and organisations in Kuwait: exploring the impact on human resource management, knowledge sharing, innovation and organisational commitment
This thesis examines the influence of wasta on employees and organisations in Kuwait. Wasta is a set of personal networks based on family or connections in which power and influence is used to accomplish things. As wasta evolved, it became deeply rooted in Kuwait. For instance, it became a tool which people use to get recruited in any position, regardless of their qualification. It is considered as a family obligation, a technique for doing business, and a practice which people use to maintain one s status. To date, there has been little research on the influence of wasta within organisations in terms of human resource management (HRM) practices, knowledge sharing, innovation, and organisational commitment in Kuwait. Consequently, the aim of this thesis is to address the research question: does wasta influence human resource management practices, knowledge sharing, innovation, and organisational commitment in Kuwait?
A mixed method sequential exploratory research design is utilised to examine the specified research question. The justification behind this approach is that both qualitative and quantitative strategies supplement each other by giving a more in-depth and complete picture of the topic. Based on a total of 343 individual responses, the outcomes identified with wasta in businesses are considerable, as it does not only impact employees performance, but also the entire organisation s performance. The findings revealed that wasta influences HRM practices, knowledge sharing, innovation, and organisational commitment in Kuwait. In addition, the results of this study developed new models that fit within the context of this research and suggests several recommendations that could be developed to reduce the unwanted effects of wasta and improve employees as well as organisations performance.
Consequently, this thesis provides a conceptual framework of what wasta is, how it is being executed, and ways in which it impacts employees and organisations in terms of the measured variables. It aims to deliver insight for citizens, employees, local and multi-national organisations, and the government in Kuwait about how the practice of wasta impacts performance, either positively or negatively. This thesis contributes to new knowledge within the field of business in the Middle East and provides a basis on which further research could be carried out. Therefore, this research will support and provide additional value to the minimum research that is available on wasta in Kuwait and worldwide
Modeling and solving a vehicle-sharing problem
Motivated by the change in mobility patterns, we present a new modeling
approach for the vehicle-sharing problem. We aim at assigning vehicles to
user-trips so as to maximize savings compared to other modes of transport. We
base our formulations on the minimum-cost and the multi-commodity flow problem.
These formulations make the problem applicable in daily operations. In the
analysis we discuss an optimal composition of a shared fleet, restricted sets
of modes of transport, and variations of the objective function
Primordial power spectrum and cosmology from black-box galaxy surveys
We propose a new, likelihood-free approach to inferring the primordial matter
power spectrum and cosmological parameters from arbitrarily complex forward
models of galaxy surveys where all relevant statistics can be determined from
numerical simulations, i.e. black-boxes. Our approach, which we call simulator
expansion for likelihood-free inference (SELFI), builds upon approximate
Bayesian computation using a novel effective likelihood, and upon the
linearisation of black-box models around an expansion point. Consequently, we
obtain simple "filter equations" for an effective posterior of the primordial
power spectrum, and a straightforward scheme for cosmological parameter
inference. We demonstrate that the workload is computationally tractable, fixed
a priori, and perfectly parallel. As a proof of concept, we apply our framework
to a realistic synthetic galaxy survey, with a data model accounting for
physical structure formation and incomplete and noisy galaxy observations. In
doing so, we show that the use of non-linear numerical models allows the galaxy
power spectrum to be safely fitted up to at least
/Mpc, outperforming state-of-the-art backward-modelling techniques by a
factor of in the number of modes used. The result is an unbiased
inference of the primordial matter power spectrum across the entire range of
scales considered, including a high-fidelity reconstruction of baryon acoustic
oscillations. It translates into an unbiased and robust inference of
cosmological parameters. Our results pave the path towards easy applications of
likelihood-free simulation-based inference in cosmology. We have made our code
pySELFI and our data products publicly available at
http://pyselfi.florent-leclercq.eu.Comment: 22 pages, 12 figures. Matches MNRAS published version. The main
results are equations (25), (26), and figure 10. The pySELFI code is publicly
available on the first author's website (currently
http://pyselfi.florent-leclercq.eu) and on GitHub
(https://github.com/florent-leclercq/pyselfi/
SHARP -- VII. New constraints on the dark matter free-streaming properties and substructure abundance from gravitationally lensed quasars
We present an analysis of seven strongly gravitationally lensed quasars and
the corresponding constraints on the properties of dark matter. Our results are
derived by modelling the lensed image positions and flux-ratios using a
combination of smooth macro models and a population of low-mass haloes within
the mass range 10^6 to 10^9 Msun. Our lens models explicitly include
higher-order complexity in the form of stellar discs and luminous satellites,
as well as low-mass haloes located along the observed lines of sight for the
first time. Assuming a Cold Dark Matter (CDM) cosmology, we infer an average
total mass fraction in substructure of f_sub = 0.012^{+0.007}_{-0.004} (68 per
cent confidence limits), which is in agreement with the predictions from CDM
hydrodynamical simulations to within 1 sigma. This result is closer to the
predictions than those from previous studies that did not include line-of-sight
haloes. Under the assumption of a thermal relic dark matter model, we derive a
lower limit on the particle relic mass of m th > 5.58 keV (95 per cent
confidence limits), which is consistent with a value of m_th > 5.3 keV from the
recent analysis of the Ly-alpha forest. We also identify two main sources of
possible systematic errors and conclude that deeper investigations in the
complex structure of lens galaxies as well as the size of the background
sources should be a priority for this field.Comment: 14 pages, 7 figures, accepted for publication in MNRA
Modeling and solving the multimodal car- and ride-sharing problem
We introduce the multimodal car- and ride-sharing problem (MMCRP), in which a
pool of cars is used to cover a set of ride requests, while uncovered requests
are assigned to other modes of transport (MOT). A car's route consists of one
or more trips. Each trip must have a specific but non-predetermined driver,
start in a depot and finish in a (possibly different) depot. Ride-sharing
between users is allowed, even when two rides do not have the same origin
and/or destination. A user has always the option of using other modes of
transport according to an individual list of preferences.
The problem can be formulated as a vehicle scheduling problem. In order to
solve the problem, an auxiliary graph is constructed in which each trip
starting and ending in a depot, and covering possible ride-shares, is modeled
as an edge in a time-space graph. We propose a two-layer decomposition
algorithm based on column generation, where the master problem ensures that
each request can only be covered at most once, and the pricing problem
generates new promising routes by solving a kind of shortest path problem in a
time-space network. Computational experiments based on realistic instances are
reported. The benchmark instances are based on demographic, spatial, and
economic data of Vienna, Austria. We solve large instances with the column
generation based approach to near optimality in reasonable time, and we further
investigate various exact and heuristic pricing schemes
Cosmology from Large Populations of Galaxy-Galaxy Strong Gravitational Lenses
We present a forecast analysis on the feasibility of measuring the
cosmological parameters with a large number of galaxy-galaxy scale strong
gravitational lensing systems. Future wide area surveys are expected to
discover and measure the properties of more than 10 000 strong lensing systems.
We develop a hierarchical model that can simultaneously constrain the lens
population and cosmological parameters by combining Einstein radius
measurements with stellar dynamical mass estimates for every lens.
Marginalizing over the lens density profiles and stellar orbital anisotropies,
we find that can be constrained to a precision of with 10 000
galaxy-galaxy lens systems, which would be better than any existing
single-probe constraint. We test our method on 161 existing lenses, finding
. We also show how to mitigate against the potential systematic
of redshift evolution in the mean lens density profile of the population
Multiple Symmetric Lipomatosis: New Classification System Based on the Largest German Patient Cohort
Background:
Multiple symmetric lipomatosis (MSL) is defined as a disorder of nonencapsulated adipose tissue growth. Its prevalence is indicated as 1:25,000 and affects, as stated in the literature, mainly Mediterranean males (male:female ratio of 15:1). Phenotypes are still classified as defined by Donhauser in 1991. We report clinical and phenotypic data of the largest patient cohort investigated in Germany so far.
Methods:
Forty-five patients diagnosed with MSL at the University Hospital Regensburg between 2007 and 2017 were photographed, clinically examined, and blood samples were taken. Based on the photographs (n = 33), 11 independent observers assessed patients using the Donhauser classification. Furthermore, the bodies of all patients were subdivided into 12 body areas, and the viewers had to indicate all MSL-affected areas per patient. Prevalence was calculated, comorbidities were assessed, and blood samples were analyzed.
Results:
According to the established Donhauser classification, less than 50% of the patients could be classified. Therefore, based on the constellations of MSL-affected body areas, a new classification that divides phenotypes of MSL into 5 types (Ia, Ib, Ic, II, and III) was set up and was able to cover 100% of our patients. The male to female ratio was found to be 1:2.5 (male:female). Prevalence of MSL in the catchment area was found to be 1:25,000. Hypercholesterinemia and hypothyroidism were frequent comorbidities, and blood analyses were normal besides a hypercholesterinemia.
Discussion:
The new proposed classification system describes 5 subtypes and allowed to classify all assessed patients. Male to female ratio (1:2.5) contradicted most previous publications
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