TCP Congestion Control Identification

Transmission Control Protocol (TCP) carries most of the traffic on the Internet these days. There are several implementations of TCP, and the most important difference among them is their mechanism for controlling congestion. One of the methods for determining type of a TCP is active probing. Active probing considers a TCP implementation as a black box, sends different streams of data to the appropriate host. According to the response received from the host, it figures out the type of TCP version implemented. TCP Behavior Inference Tool (TBIT) is an implemented tool that uses active probing to check the running TCP on web servers. It can check several aspects of the running TCP including initial value of congestion window, congestion control algorithm, conformant congestion control, response to selective acknowledgment, response to Explicit Congestion Notification (ECN) and time wait duration. In this paper we focus on congestion control algorithm aspect of it, explain the mechanism used by TBIT and present the results

Interpreting Measurements of Small Strain Elastic Shear Modulus under Unsaturated Conditions

Bender element testing of unsaturated isotropically compacted speswhite kaolin samples was used to investigate the variation of small strain elastic shear modulus G under unsaturated conditions. Testing was performed in a suction-controlled triaxial cell and involved combinations of isotropic loading and unloading stages and wetting and drying stages. Analysis of the experimental results indicated that the variation of G could be represented by a simple expression involving only mean Bishop’s stress p* and specific volume v, with the only significant mismatches between measured and predicted values of G occuring at the end of final unloading. No significant improvement of fit was achieved by incorporating additional dependency on degree of saturation Sr or a bonding parameter ζ. The proposed expression for G reverts to a well-established form for saturated soils as Sr tends to 1

Drillstring Vibration Analysis in Extended Reach Drilling (ERD) using WELLPLANTM

Oil and gas industry always aims efficient service with optimal expenses. This final year project, aiming to deal with one of the most important parameters, that has tremendous impact on drilling operations’ time and cost. This parameter as mentioned above on the topic is a Drillstring Vibrations. While drilling, Drillstring Vibration causes premature drillstring components and bit failure [8], and is a waste of drilling energy. To increase drilling efficiency, drillstring vibrations need to be monitored and analyzed and the optimum drilling parameters and practices need to be achieved as a well is being drilled. This results in a reduction in the drillstring failures and the amount of time spent tripping and/or fishing, and an increase in both bit life and drilling rate. Drillstring dynamics is one of the most important limiting factors in extended reach drilling. This is because, long sections of the drillstring lie on the low side of the wellbore while rotating. When the rotary speed exceeds a critical threshold the drillstring starts to snake, sliding up and down the borehole wall [1]. If rotated further beyond the threshold speed, the drillstring will eventually start to whir which can cause severe damage to string components after only a short period of time [1]. Therefore, the main scope of the project, considering the earlier mentioned issues, a WELLPLAN software (Critical Speed Module) used. The project mainly dealt with drillstring, axial stress, bending stresses and torsional oscillations known as stick-slip motion of the bit. Besides the WELLPLANTM software, a matlab M.file was developed that uses some predetermined equations to estimate the critical drillstring vibrations, and critical operational speed taking into account the weight on bit, BHA length and rock compressive strengt

Black Hole with Quantum Potential

In this work, we investigate black hole (BH) physics in the context of quantum corrections. These quantum corrections were introduced recently by replacing classical geodesics with quantal (Bohmian) trajectories and hence form a quantum Raychaudhuri equation (QRE). From the QRE, we derive a modified Schwarzschild metric, and use that metric to investigate BH singularity and thermodynamics. We find that these quantum corrections change the picture of Hawking radiation greatly when the size of BH approaches the Planck scale. They prevent the BH from total evaporation, predicting the existence of a quantum BH remnant, which may introduce a possible resolution for the catastrophic behavior of Hawking radiation as the BH mass approaches zero. Those corrections also turn the spacelike singularity of the black hole to be timelike, and hence this may ameliorate the information loss problem.Comment: 16 pages, 6 figures; Accepted in Nucl.Phys.