Tree Collision Research Articles

Hybrid Collision Avoidance-Tree Resolution for M2M Random Access

Wireless machine-to-machine (M2M) communication with synchronized traffic patterns plays an important role in many aircraft systems. Recent research has separately examined collision avoidance mechanisms, such as presmoothing and access barring, as well as collision resolution mechanisms, such as tree resolution, for M2M random access. In contrast, we examine the combination of collision avoidance and tree collision resolution into hybrid M2M random access protocols in the context of the popular Long-Term Evolution wireless system.

The Throughput Analysis of IBTCRPP-CSMA in Ad Hoc Network

From the point of view to improve QoS of Ad Hoc network, this paper analyses the problem about mobile nodes in Ad Hoc network and decides to solve the problem by designing effective MAC protocol. Therefore, a novel random multi-access protocol using Binary Tree Collision Resolution for collision packets in Probability-Persistent Random Multi-Access (IBTCRPP-CSMA) is proposed. The throughput of IBTCRPP-CSMA and computer simulation experiments are obtained. Simulation results agree with theoretical analysis. By contrasts of throughputs among several CSMA protocols, IBTCRPP-CSMA has higher throughput and channel utilization, thereby ensuring the system’s high QoS.

The application of energy-absorbing structures on side impact protection systems

This paper presents a system to improve the protection to the occupants of a World Rally Championship Car in case of a side impact involving a tree collision using energy-absorbing structures. An outline of the immediate events after the car crash into a tree is provided followed by an analysis of a typical standard rollcage, then the design criteria and features of a carefully selected design concept. The design model is produced using solid modelling/I-DEAS 11 softwares and PAM-Crash is used for the simulations. The simulation results show that Side Impact Protection System (SIPS) is capable of absorbing and dissipating 98% of the energy of a 14 m/s impact involving a 0.2 m diameter tree.

An efficient framed-slotted ALOHA algorithm with pilot frame and binary selection for anti-collision of RFID tags

Reducing the number of tag collisions is one of the most important issues in RFID systems, as collisions induce inefficiency. This paper presents a mechanism of grouping of tags via a bit mask, quick tag estimation by a pilot frame and near optimal binary tree-based collision resolution with a frame. Performance analysis and simulation results show that the proposed anti-collision algorithm consumes fewer time slots as compared to previous work, and approaches to the case with the optimal frame size using binary tree collision resolution.

A simple performance analysis of RFID networks with binary tree collision arbitration

Radio Frequency Identification (RFID) networks are becoming a widespread technology in industry and commerce. In this paper, we propose a simple performance analysis of RFID networks, based on the binary tree collision arbitration protocol. We evaluate various network performance metrics such as throughput, delay and average number of packets needed to take a census of the RFID tags. In order to validate our analytical results, we develop a simple, yet accurate, simulator and show that the predicted analytical performance is in good agreement with the simulation results. While the analytical approach does not take into account the communication channel characteristics, we evaluate, through simulations, the impact of fading and topology (in terms of tag spatial density) on the network performance.

Baumunfälle im Straßenverkehr - Unfallmechanismus und Verletzungsmuster

In Germany, the county of Mecklenburg-Vorpommern has got the highest frequency of traffic accidents. 42 % of all deadly injured car accident victims in Mecklenburg-Vorpommern sustained a tree collision. Aim of this study was to analyze tree collisions regarding typical pattern and severity of injury. During an on-going prospective, non-interventional accident survey within a defined area of the county of Mecklenburg-Vorpommern tree collisions with minimum one victim sustaining a Maximum Abbreviated Injury Scale of 1-6 injury were analyzed. In between January 2001 and June 2004 287 accidents were documented. 19 % (54) were tree collisions. 81 % of drivers were male. 36 of 54 tree collisions (67 %) occurred on straight roadways. The mean ISS was 31.3 (SD +/- 29.8), 30 % (23) of the passengers died. 70 of 78 individuals sustained more than one injury. With that, the combination of head- and chest trauma was most frequent and associated with the highest injury severity. Especially tree collisions lead to severe trauma. Interestingly, most accidents did occur on straight roadways.

SHOULDER PAIN AND WEAKNESS - ADVENTURE RACING

HISTORY A 35 year-old right-handed elite adventure racer sustained a left shoulder injury while mountain biking when he collided into a tree with his left anterior shoulder. Three weeks prior he had bruised his left face and strained his left neck when he collided with a tree. The shoulder/neck pain associated with both incidents was mild and resolved within several days. Two weeks following the second tree collision, the patient developed severe left shoulder pain, weakness, and dysesthesias involving the proximal upper extremity immediately following a swimming session. Over the next two week, opiate medication was necessary to control the pain and provide satisfactory sleep. Four weeks later he presented to this clinic with no significant improvement in his symptoms. He denied parasthesias or weakness in the other limbs. He was otherwise in good health. PHYSICAL EXAMINATION Examination in our clinic revealed mild atrophy of the left supraspinatus and infraspinatus muscles with normal active external rotation. Testing of the other muscles in the upper limbs tested revealed normal 5/5 strength. Sensation was intact bilaterally to light touch and pin prick and muscle stretch reflexes were 2+/4 and symmetric ROM of the upper extremities. Manual muscle testing was 4/5 for left shoulder abduction and 3/5 for left shoulder. Palpation revealed no tenderness in the left upper extremity, shoulder girdle or cervical paraspinal muscles. Spurling's test was significant for axial cervical pain, bilaterally. He had a mildly positive impingement sign for the right shoulder. Anterior apprehension test, anterior/posterior load and shift tests, and O'Brien's test were negative. DIFFERENTIAL DIAGNOSIS Rotator cuff tendinopathy or tear. Upper cervical radiculopathy. Suprascapular neuropathy. Brachial neuritis. Upper cervical plexopathy. TESTS AND RESULTS Radiographs of cervical spine and left shoulder: normal, MRI of cervical spine: mild left C6 foraminal stenosis. MRI of left shoulder: no evidence of rotator cuff pathology, spinoglenoid cysts, or labrum tear. Electrodiagnostic testing: – conduction delay of the left suprascapular nerve, with 50% less amplitude in the motor unit potential, compared to the right, – 2+ spontaneous denervation activity in the left supraspinatus and infraspinatus muscles, with mild evidence of reinnervation. – normal conduction study of other peripheral nerves and normal needle electromyography study in other left upper limb and cervical paraspinal muscles. FINAL DIAGNOSIS Left suprascapular neuropathy with some axonal loss. TREATMENT AND OUTCOMES Utilization of NSAIDs and opiates for pain control. Relative rest from physical activity for the next 4 weeks. Physical therapy for strengthening exercises focusing on the supraspinantus and infraspinatus muscles. Return to sports activities by 4 weeks. Patient became pain free within two months. Repeat electrodiagnostic tests 5 months after onset of pain revealed complete reinnervation of the supraspinatus muscle, but incomplete reinnervation of the infraspinatus muscle, which showed continued spontaneous activity and polyphasic motor units. Recovery of full strength of supraspinatus muscle within 8 months, but only moderate recovery of strength of infraspinatus muscle.

Save the Trees

From 1981 to 1989, 323 patients whose diagnoses resulted from ski injuries were emergently admitted to a Class 1 Trauma Hospital. Of this group, 107 (33%) were injured in skier-tree collisions. This tree collision group (TC group) was compared with a group that did not hit a tree (non-tree-collision group or NTC group). The average age of the TC group was 26 years, compared with 31 years in the NTC group. The Revised Trauma Score (RTS) was recorded for each patient. The TC group's average trauma score was 7.205, compared with 7.7395 for the NTC group. The Injury Severity Score (ISS) was also recorded. The TC group's ISS averaged 14.7, compared with 9.1 for the NTC group. Both of these scores demonstrated statistical significance. Certain injuries such as skull fractures, head injuries, pelvic fractures, and chest injuries (including rib fractures, pneumothoraces, and pulmonary contusions) were more common in the TC group. Tibia fractures were more common in the NTC group. Femur fractures and upper extremity fractures were evenly distributed between the two groups. Seven deaths were recorded in the TC group and five deaths occurred in the NTC group.

The robustness and performance of tree collision resolution algorithms in an unshared feedback error environment

This paper discusses in detail the robustness of the Capetanakis Collision Resolution Algorithm (CCRA) with and without the arrival epoch modification for multiple access networks. In particular, we show that the algorithm is robust against errors that cause different stations to see different feedback information about the results of the transmission attempts, and we quantify, through simulations and analysis, the performance (throughput/delay) degradation caused by those unshared errors.

Urban Trees and Roadside Safety

This paper describes a research project performed as part of a clear zone implementation program for Huntsville, Alabama. A literature review and a field investigation program were the two major components of the project. Investigators visited the sites of 164 urban tree accidents to identify their characteristics. Time of day, day of week, accident severity, roadway geometry, pavement surface condition, lateral distance from the pavement to the tree, tree size, and tree density were among the characteristics investigated. Among the major findings were that: there were strong similarities between urban and rural tree collision patterns, but urban accidents were less severe; the outside of horizontal curves was highly over‐represented; and 80% of the collisions were within 20 ft of the pavement edge. Recommendations were provided for city ordinances and operating procedures for future tree plantings. A plan was also devised for retrofitting the clear zone concept to existing trees along city streets.

Deterministic vs. probabilistic tree collision resolution algorithms

Deterministic vs. probabilistic tree collision resolution algorithms