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THz band is envisioned to be used in 6G systems to meet the ever-increasing demand for data rate. However, before an eventual system design and deployment can proceed, detailed channel sounding measurements are required to understand key channel characteristics. In this paper, we present a first extensive set of channel measurements for urban outdoor environments that are ultra-wideband (1 GHz 3dB bandwidth), and double-directional where both the transmitter and receiver are at the same height. In all, we present measurements at 38 Tx/Rx location pairs, consisting of a total of nearly 50,000 impulse responses, at both line-of-sight (LoS) and non-line-of-sight (NLoS) cases in the 1-100 m range. We provide modeling for path loss, shadowing, delay spread, angular spread and multipath component (MPC) power distribution. We find, among other things, that outdoor communication over tens of meters is feasible in this frequency range even in NLoS scenarios, that omni-directional delay spreads of up to 100 ns, and directional delay spreads of up to 10 ns are observed, while angular spreads are also quite significant, and a surprisingly large number of MPCs are observed for 1 GHz bandwidth and 13 degree beamwidth. These results constitute an important first step towards better understanding the wireless channel in the THz band.

A highly automated diagnostic methodology that reduces No Trouble Found (NTF) rates in hyper-scale data centers and provides faster quality response including failure analysis to suppliers for PAM4 based optical transceivers (200G/400G) is presented.

We consider a class of singularly perturbed 2-component reaction-diffusion equations which admit bistable traveling front solutions, manifesting as sharp, slow-fast-slow, interfaces between stable homogeneous rest states. In many example systems, such as models of desertification fronts in dryland ecosystems, such fronts can exhibit an instability by which the interface destabilizes into fingering patterns. Motivated by the appearance of such patterns, we propose two versions of a 2D stability criterion for (transversal) long wavelength perturbations along the interface of these traveling slow-fast-slow fronts. The fronts are constructed using geometric singular perturbation techniques by connecting slow orbits on two distinct normally hyperbolic slow manifolds through a heteroclinic orbit in the fast problem. The associated stability criteria are expressed in terms of the nonlinearities of the system and the slow-fast-slow structure of the fronts. We illustrate and further elaborate the general set-up by explicitly working out the existence and transversal (in)stability of traveling fronts in a number of example systems/models. We analytically establish the instability of invading bare soil/vegetation interfaces against transversal long wavelength perturbations in several dryland ecosystem models and numerically recover fingering vegetation patterns counter-invading an invading desertification front.

Facebook Datacenter consists of a large number of servers that run diverse Facebook services aggregated to serve any given user request. To allow this aggregation, servers have to interact with each other via different traffic flows which are managed by networking fabric. The underlying connection powering this fabric consists of a large number of pluggable optical interconnects and On Board Optical (OBO) modules carrying production data. This connectivity at scale requires fast and reliable detection of the link failures to ensure resolution. In the first generation of the deployments, detection of the link failure was sequential and a slow process. The troubleshoot process was equally tedious as the available tools required characterizing one optical transceiver at a time. Further, the failure analysis also presented a majority of resolution with no failed optics as a root cause resulting in high No Trouble Found (NTF) rate. In this paper we introduce a novel link failure detection and resolution method that improves on the previous method across three dimensions: faster resolution, reliable troubleshooting and scalable implementation. We introduce BER Illusion Methodology (BIM) that is a highly scalable and resource efficient solution that significantly reduces the time taken to troubleshoot pluggable optical interconnects. This is also scalable to next-gen OBO modules at Facebook datacenters aiming to lower the NTF rate and optimally utilizing the available resources. BIM, which is based on Open Compute Platform (OCP) network switches, can be used to troubleshoot 128 QSFP28, 64 QSFP56 or 32 OBO modules simultaneously in under 30 minutes. The tool is easy to implement and capable of also reporting diagnostics on the transceiver such as Transmitter Power, Transmitter Bias Current, Receiver Power, Case Temperature, Bit Error Rate result per channel, Vendor information and Manufacturing part number. This additional test data report along with true failure indication helps optic suppliers gain confidence and build customer credibility. The open-source nature and the universal applicability of this tool offers possibility for other users to adopt and further customize it for their networking needs.

Cholesteatoma is a common benign lesion of the middle ear characterised by accumulation of keratinous debris. It is associated with local bony erosions and hence serious intracranial and labyrinthine complications which prompts surgical intervention. Earlier, High resolution computed tomography (HRCT) was used in combination with clinical examination to arrive at a diagnosis. Computed tomography (CT) gives excellent definition of bony structures, but lacks sensitivity in differentiating between various causes of soft tissue densities. Magnetic resonance imaging (MRI) is more useful in evaluation of soft tissue details. We conducted this study with an aim of evaluating the role of diffusion weighted imaging in diagnosis of cholesteatoma and its utility to differentiate cholesteatoma from granulation/ inflammatory tissue. The study was conducted on forty patients between March 2018 and February 2019 who were clinically suspected of chronic suppurative otitis media with cholesteatoma. These patients were subjected to HRCT and Diffusion weighted MRI (DW-MRI) examination of temporal region and findings were correlated with intraoperative and histological features. Our study found that, HRCT had a sensitivity of 83.3% and specificity of 58.3% in detection of cholesteatoma, while MRI was found to accurately predict the presence of cholesteatoma in 91.6% of the cases evaluated. The sensitivity, specificity, positive predictive value and negative predictive value were 91.6%, 91.6%, 95.6% and 84.6%, respectively. Hence, we conclude that diffusion weighted magnetic resonance imaging is a useful technique for cholesteatoma imaging with high sensitivity and specificity. Combination of HRCT and MRI will be helpful to make an accurate diagnosis.

The utilization of distributed computing server farm is developing quickly to fulfill the large increment required for systems administration, High-Performance Computing(HPC) as well as stockpiling assets for executing business and logical applications. The process of Virtual Machine (VM) solidification is inclusive of VMs getting relocated in order to make use of less physical servers. As a result, it enables the shut down or lowpower mode of more number of servers which enhances the vitality utilization effectiveness, working expense and CO2 discharge. An urgent advance in VM union is have over-burden discovery, which endeavors to foresee whether a physical server is going to be oversubscribed with VMs. On the contrary to usual studies which performed utilization of CPU being the standalone indicator for host overload, a multiple correlation host overload detection algorithm was proposed in the recent study by considering a lot of factors in this regard. A higher load balance model was introduced in this text for the general public cloud, supported by the concept of cloud partitioning, in addition to a switch mechanism used to strategize differently under different scenarios. The IP address is generally shared by a true server and carbo balance. In this regard, the load balancer considers the interface developed with IP address which accepts request packets and the packets are directed to the selected servers. With an aim to improve the efficiency in public cloud environment, the algorithm employed the sport theory in the load balancing strategy.