A cross layer multi hop network architecture for wireless Ad Hoc networks

In this paper, a novel decentralized cross-layer multi-hop cooperative network architecture is presented. Our architecture involves the design of a simple yet efficient cooperative flooding scheme,two decentralized opportunistic cooperative forwarding mechanisms as well as the design of Routing Enabled Cooperative Medium Access Control (RECOMAC) protocol that spans and incorporates the physical, medium access control (MAC) and routing layers for improving the performance of multihop communication. The proposed architecture exploits randomized coding at the physical layer to realize cooperative diversity. Randomized coding alleviates relay selection and actuation mechanisms,and therefore reduces the coordination among the relays. The coded packets are forwarded via opportunistically formed cooperative sets within a region, without communication among the relays and without establishing a prior route. In our architecture, routing layer functionality is submerged into the MAC layer to provide seamless cooperative communication while the messaging overhead to set up routes, select and actuate relays is minimized. RECOMAC is shown to provide dramatic performance improvements, such as eight times higher throughput and ten times lower end-to-end delay as well as reduced overhead, as compared to networks based on well-known IEEE 802.11 and Ad hoc On Demand Distance Vector (AODV) protocols

RECOMAC: a cross-layer cooperative network protocol for wireless ad hoc networks

A novel decentralized cross-layer multi-hop cooperative protocol, namely, Routing Enabled Cooperative Medium Access Control (RECOMAC) is proposed for wireless ad hoc networks. The protocol architecture makes use of cooperative forwarding methods, in which coded packets are forwarded via opportunistically formed cooperative sets within a region, as RECOMAC spans the physical, medium access control (MAC) and routing layers. Randomized coding is exploited at the physical layer to realize cooperative transmissions, and cooperative forwarding is implemented for routing functionality, which is submerged into the MAC layer, while the overhead for MAC and route set up is minimized. RECOMAC is shown to provide dramatic performance improvements of eight times higher throughput and one tenth of end-to-end delay than that of the conventional architecture in practical wireless mesh networks

Energy distribution control in wireless sensor networks through range optimization

A major objective in wireless sensor networks is to find optimum routing strategies for energy efficient use of nodes. Routing decision and transmission power selection are intrinsically connected since the transmission power of a node is adjusted depending on the location of the next hop. In this paper, we propose a location-based routing framework to control the energy distribution in a network where transmission ranges, hence powers, of nodes are determined based on their locations. We show that the proposed framework is sufficiently general to investigate the minimum-energy and maximum-lifetime routing problems. It is shown that via the location based strategy the network lifetime can be improved by 70% and the total energy consumption can be decreased to three-fourths to one-third of the constant transmission range strategy depending on the propagation medium and the size of the network

Throughput analysis of ALOHA with cooperative diversity

Cooperative transmissions emulate multi-antenna systems and can improve the quality of signal reception. In this paper, we propose and analyze a cross layer random access scheme, C-ALOHA, that enables cooperative transmissions in the context of ALOHA system. Our analysis shows that over a fading channel C-ALOHA can improve the throughput by 30%, as compared to standard ALOHA protocol

Stable Optical Frequency Comb Generation And Applications In Arbitrary Waveform Generation, Signal Processing And Optical Data M

This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was ±1 MHz, limited by the electronic waveform generator, and the RF carrier frequency is limited by the bandwidth of the photodetector. Similarly, using parabolic phase modulation together with time division multiplexing, RF chirp extension has been realized. Another application of the optical frequency combs studied in this thesis is real time data mining in a bit stream. A novel optoelectronic logic gate has been developed for this application and used to detect an 8 bit long target pattern. Also another approach based on orthogonal Hadamard codes have been proposed and explained in detail. Also novel intracavity modulation schemes have been investigated and applied for various applications such as a) improving rational harmonic modelocking for repetition rate multiplication and pulse to pulse amplitude equalization, b) frequency skewed pulse generation for ranging and c) intracavity active phase modulation in amplitude modulated modelocked lasers for supermode noise spur suppression and integrated jitter reduction. The thesis concludes with comments on the future work and next steps to improve some of the results presented in this work

Effects of total knee arthroplasty on ankle alignment in patients with varus gonarthrosis : do we sacrifice ankle to the knee?

Total knee arthroplasty is one of the most commonly preferred surgical methods in the treatment of patients with varus gonarthrosis. In this study, we aimed to evaluate the radiological changes observed in the ankles after total knee arthroplasty. Between May 2012 and June 2013, 80 knees of 78 patients with varus deformity over 10A degrees underwent total knee arthroplasty. For each patient, full-leg standing radiographs were obtained pre- and post-operatively. Mechanical and anatomical axes (HKA and AA), lateral distal femoral angle, medial proximal tibial angle, lateral distal tibial angle (LDTA), ankle joint line orientation angle (AJOA), tibial plafond talus angle (PTA) and talar shift were measured for each patient both pre- and post-operatively. Pre-operatively, the mean HKA was 16.6A degrees and the mean AA was 10.41A degrees, both in favour of varus alignment. Post-operatively, the mean HKA decreased to 3.6A degrees and the mean AA to -2.1. The mean LDTA was 87.3A degrees. Before the operation, the mean AJOA was -7.6A degrees, opening to the medial aspect of the ankle, and it was 0.04A degrees after the operation and opening to the lateral aspect (p < 0.05). Our study reveals the changes occurring in the ankle after acute correction of long-standing varus deformity of the knee using total knee arthroplasty. In cases undergoing knee arthroplasty, effect of the acute change in the alignment of the knee on the ankle should be taken into consideration and the amount of correction should be calculated carefully in order not to damage the alignment of the ankle

How about nano? Impact of size of plastics on plastic pollution and the magnitude of the problem

In the last decade we have realized that the plastics we use every day, and for practically everything, may be the biggest environmental polluters humans have ever released to the environment (EU DG, 2011). Since the first reports of plastic pollutions, we have learned so much about the issue. Macro and micro plastic pollution topics have been extensively studied, investigated, regulated, and in some cases litigated (Uren Webster et al., 2020)(Barnes, Galgani, Thompson, Barlaz, 2009)(Environment Agency, 2018). As it happened in most of the past cases, we have started with the most obvious and visible problem: macro plastics

Hemostasis in Cardiac Surgery: How We Do it with Limited Resources

Hemostasis in cardiac surgery is still a severe problem for surgeons. Blood and its products are the most valuable at the same time dangerous arms of surgeons. Industries produced many biological or non-biological products, which increase the cost of operations, are available for this issue. Decision making and producing solutions must be the most important properties of a cardiac surgeon. In any condition and resources, true strategy and patience will bring the success. Antiaggregants and anticoagulants are widely used agents, and in emergency or early cases, surgeons have to operate these patients. Both groups of drugs are growing, and in an emergency position, it is hard to know which drugs the patient using or given and what kind of medical status he/she has. For example non vitamin-K oral anticoagulants newer drugs and not known so much except cardiologists and cardiovascular surgeons. Simple solutions may have better results. Of course, in some conditions, urgent consultation can solve the problem. Cardiac surgeons have to figure out the problem by using their experience and surgical materials. Working as a team is a big advantage, more than one surgeon, experienced operation nurses and closer follow up in intensive care unit

Management of Pediatric Appendicitis

Appendicitis is the most common surgical diagnosis for children who present with abdominal pain to the emergency department. However, there are nonspecific examination findings and variable historical features during its presentation. Diagnosis of appendicitis in the pediatric patient may be challenging for the clinician dealing with these children. It is important to have a high index of suspicion and taking a detailed history and physical examination. In diagnosis of appendicitis, adjunctive studies that may be useful are the white blood cell count, C-reactive protein, urinalysis, ultrasonography and computerized tomography when necessary. When appendicitis is suspected, patients should receive immediate surgical consultation, as well as volume replacement and antibiotics if indicated. The most accurate diagnostic tool is perhaps the serial examinations by the same examiner. With this timely approach, it will be possible to prevent the significant morbidity that is associated with delayed diagnoses in younger patients