Rear Shield Research Articles

A new genus and new species of eriophyid mites from Papua New Guinea: a potential biological control agent of Falcataria moluccana (Fabaceae)

A new genus and species of the subfamily Nothopodinae, Colopodacini from Papua New Guinea are described and illustrated. Solenidiversum falcatariae gen. nov. sp. nov. infests Falcataria moluccana (Miq.) Barneby and Grimes (Fabaceae) and causes erineum on both the leaf surfaces. Solenodiversum gen. nov. has the solenidion on the inner side of tarsus I, tibiae of both legs completely fused with tarsus, all leg and ventral opisthosomal setae present, empodium entire and scapular tubercles on rear shield margin. With this new genus and species, the current number of Colopodacini is 16 genera and 41 species. A key to the genera of the Colopodacini tribe is given.

Lesch-Nyhan Syndrome: Evaluation of a Modified Bite Device to Prevent Bite Injuries

Lesch-Nyhan syndrome (LNS) is a serious form of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency, a hereditary purine metabolism disorder. The prevalence reported in the literature is 1/380,000 to 235,000 births. Males are affected and females are heterozygous carriers. LNS patients present a combination of hypotonia, spasticity, and neurological and behavioral disorders. They also show an obsessive-compulsive self-injurious behavior with bites and injuries to the lips, tongue, cheeks and fingers. The literature offers little scientific contribution related to the management of this problem. The authors describe their experience with a 4-year-old LNS patient and present a viable solution to control and avoid bite injuries, namely a specifically modified bite. The patient was treated at the Pediatric Dentistry Department of “Sapienza” University of Rome with a modified bite with the internal surface, in contact with the teeth, realized in 2-mm-thick soft silicone, and the exterior part consisting of a transparent resin shell with front and rear shields to separate lips and cheeks from the dental arches. At a 12-month follow-up visit, compliance was excellent: the child wore the device with regularity and without discomfort, even during soft-food feeding. No intraoral bite injuries were found, with a general improvement of the young patient’s quality of life.

Numerical analysis of hard rock tunnel excavated by double shield TBM based on CWFS model

In order to study the mechanical response of a hard rock tunnel excavated by double shield tunnel boring machine (DS-TBM), a numerical method was introduced to simulate the TBM excavating process. The failure modes of surrounding rock mass described based on the cohesion weakening and frictional strengthening (CWFS) Mohr-Coulomb strain-softening criterion. The characteristics of stress field and plastic zone on the cross and longitudinal section of the tunnel were analyzed in detail, and the results were compared with those in the intrinsic condition (when TBM model is not activated). The simulation results indicate that the stress paths at the vault are relatively simple, and the stress concentration caused by excavation unloading is obviously reduced by lining and backfill grouting, while the sidewall is less disturbed by the excavation of TBM. The invert experiences three unloading processes, due to excavation, the contact between the rear shield and the bottom of surrounding rock, as well as backfill grouting at gap between the lining and the rock mass. The vault has a larger plastic zone than the invert, attributing to the geometrical difference between the cutter-head and the front shield, as well as the conicity of the front and rear shields. The area of plastic zones gradually increases along the tunnel route, but it becomes stable after the rear shield.

Pattern of safety risk assessment in road fleet transportation of hazardous materials (oil materials)

PurposeOne of the most important problems in the road fleet transportation of hazardous materials is truck accidents in which the main influential factors are the type of truck and its safety conditions. This research aimed to propose the pattern of assessing safety risk of road fleet transportation of hazardous materials and classifying trucks with a safety approach. Design/methodology/approachIn this research, first the safety risk contributing factors (SRCFS) and sub-safety risk contributing factors (Sub-SRCFS) of road oil trucks were identified using job hazard analysis (JHA) method and finalized by expert consensus. Thereafter, fuzzy analytical hierarchy process (FAHP) was employed in order to weigh the determined SRCFS and Sub-SRCFS. Finally, the safety risk assessment pattern in road oil truck was presented considering failure modes and effect analysis (FMEA) approach. FindingsThe results showed that the most important SRCFS in the road fleet of hazardous materials transportation in the carrier and tank groups were “technical characteristics of the carrier” and “technical characteristics of the tank”. In addition, the most important Sub-SRCFS included unsuitable inspection of the truck (tank and carrier), poor brake system, and lack of the strength of front and rear shields of the carrier. Originality/valueThe results showed that the main causes of increased accident risk are the lack of use of front and rear shields, brake system and inappropriate inspections. The lack of systematic inspection can be the most important case to increase the risk of road transport of hazardous materials.

Development and in-situ application of a real-time monitoring system for the interaction between TBM and surrounding rock

In this study, a real-time monitoring system for the interaction between TBM (Tunnel Boring Machine) and surrounding rock is developed, in which the focus is on the cutter-head vibration, and the interaction between the surrounding rock and the shield. The monitoring system consists of sensors, data acquisition subsystem, remote data transmission-storage subsystem and data analysis subsystem. A program is developed to carry out unattended operation of the monitoring software. Further, it can transmit the data synchronously from inside the tunnel to the system outside the tunnel, as well as give feedback information of any operation error to the users automatically. The feasibility, stability, durability of the developed monitoring method has been validated. Subsequently, the time-domain and spectral frequent-domain analysis methods for the accelerated velocity of cutter-head vibration are put forward. Further, the back-calculation analyses method for the surrounding rock pressures acting on the shield and shield jamming warning approach is also developed. Then, the developed monitoring method has been implemented on the double-shield TBM in China’s Lanzhou Water Resource Project. Many evolution rules have been obtained. Firstly, the cutter-head vibration monitoring results show that: (a) the cutter-head vibration is significantly correlated with the TBM advance parameters and the geological conditions; (b) the cutter-head vibrates intensely during TBM restarting after a stoppage or entrapment; (c) the cutter-head vibration intensity increases with the increasing cutter-head rotational speed and penetration rate. Secondly, in-situ monitoring of the surrounding rock pressures acting on the shield manifests that: (a) the surrounding rock pressures acting on the shield is non-uniform, which increase with the growing distance from the tunnel face; (b) the contact scope enlarges from the front shield to the rear shield gradually with time, and the surrounding rock loads acting on the shield increases simultaneously; (c) the squeezing pressures acting on the shield decrease and then return to the relatively small pressures after the relief countermeasures were conducted on the trapped TBM. The measured data give insights on the intense cutter-head vibration warning and shield jamming prediction. Furthermore, the verifications, significances, advantages, weaknesses and future improvements of the monitoring system are discussed.

Presenting a conceptual pattern of HSE performance of oil trucks.

Accidents are among the main problems in the oil product supply chain. The most important effective factors in these events are the kind of trucks used and their health, safety, and environment (HSE) condition. The aim of this study was to present a conceptual pattern of the HSE performance of oil trucks in oil industries. In this study, 20 truck models (with fixed tanks), in use over different periods of time, were investigated. In this regard, the criteria and sub-criteria were first determined in two parts-carrier and tank-and weighted by fuzzy analytical hierarchy process (FAHP). The results showed that the most important sub-criteria regarding the HSE factors of the carrier were resistance and strength of the front and rear shields, the brake system, and the ventilation system. The most important sub-criteria regarding the HSE factors of the tank were tank shell thickness and a good tank design shape with respect to portable material. It should be noted that the weight of the criteria with each other and sub-criteria with each other are not equal. This issue is important for decision-making. The main reason for the use of trucks with the lowest score in developing countries is the lack of attention by managers to safety issues and international standards and agreements such as the ADR.

One new genus and three new species of Diptilomiopinae from Vietnam (Acari: Eriophyoidea)

In this paper, we described one new genus Babus gen. nov. from the subfamily of Diptilomiopinae by characters as below: scapular setae (sc) placed ahead of the rear shield margin, anterolateral setae on coxisternum І (1b) absent, tarsal empodium divided, legs with six segment, basiventral femoral setae (bv) and antaxial genual setae (l'') on leg II absent. Two new species, Babus chukrasium sp. nov. collected from Chukrasia tatularis A. Juss. and Babus anisatae sp. nov. from Clausena anisata (Willd.) Hook. f. ex Benth. were herein described. In addition, another new species Trimeroptes chaetophori sp. nov. collected from Rubus chaetophorus Card. was also described and illustrated from the same subfamily. All of new species described here are vagrants on the under surfaces of leaves, and no damage was observed.

Optimizing a four-props support using the integrative design approach

Modern approach to the design process of technical means requires taking into consideration the issues concerning the integration of different sources of data and knowledge, and various methodologies of design. Thus, the importance of integrative approach is growing. The integration itself could be understood as a link between these different methodological solutions. Another problem is the issue concerning the optimization of technical means because of the range of design requirements. The presented issues are the basis for design approach that uses integrative approach as the basis for constructional optimization of designed technical mean. It bases firstly on the concept of integration three main subsystems of a technical mean: structural one, drive one and control one. Secondly it includes the integration of three aspects of a construction: its geometrical characteristics, its material characteristics and its assembly characteristics. One of areas of utilization of the proposed integrative approach to designing process is elaborating the construction of mining mechanized supports. There different systems of mining support characterizing by different sets of advantages and disadvantages. The importance of the design process is considered with the working conditions of mining supports that are closely linked with geological characteristics of mined beds. A mining mechanized support could be treated as the logical union of three mentioned constructional subsystems. The structural one includes among others canopy, rear shield and foot pieces. The drive one includes hydraulic props and its equipment. Finally the control one include the system of hydraulic valves ant their parameters.

강의 레이저-아크 하이브리드 용접시 공정변수에 따른 비드용접특성 (I) - 보호가스 유량 및 레이저 아크간 거리의 영향 -

Recently many studies for improvement of productivity and automation of process are in progress, and among others, laser-arc hybrid welding that combined laser and arc has attracted much attention. Since parameters by interactions as well as the parameters of each heat source should be considered, There are a lot of hardship in actual application, even though many researches have been done so far. Therefore in this study, bead welding was done to examine the effects of the flow rate of shield gas and the distance between laser and arc during laser-arc hybrid welding. As for hybrid heat source, disk laser and MIG were used. As experiment result, sound bead and weld with no defect were formed when the flow rate of front and rear shield gas were respectively 20 l/min and 15 l/min, and deep penetration was done at DLA=3 mm.

Advance numerical simulation of tunneling by using a double shield TBM

Double shield TBMs are amongst the most technically sophisticated excavation machines in use by tunneling industry. However, using the shielded machine limits access to the walls for observation of ground conditions and presence of shield makes the machine susceptible to entrapment or seizure in weak rocks under high stresses which results in high convergence. To realistically evaluate the possibility of machine seizure in such grounds, the interaction between the rock mass and shields, lining and backfilling need to be understood. This study explains the application of numerical analysis for 3D simulation of mechanized tunneling by using a double shield TBM. For this purpose, a comprehensive numerical simulation is developed to systematically evaluate the potential of excessive ground convergence. Simulation results at five reference points on the tunnel circumference along the tunnel have been examined. The results are including longitudinal displacement profile (LDP) as well as contact force profiles (LFP) on both front and rear shields, frictional forces and required thrust to move the machine, stress history of ground, and estimated loading of the segments. The results also proved that numerical analyses can successfully be used for prediction of loads on the shield during excavation to assess risks of machine entrapment.

3D finite difference model for simulation of double shield TBM tunneling in squeezing grounds

One of the main concerns in using a shielded machine in deep rock tunnels is the possibility of the shield seizure in squeezing ground. To realistically evaluate the possibility of machine seizure in such grounds, the interaction between the rock mass and shield, lining and backfilling need to be understood. This paper will explain the background theories and the application of numerical analysis for 3D modeling of mechanized tunneling by using a double shield TBM in squeezing ground. The discussions will include the effects of advance rate during excavation cycle of a shielded TBM to observe the impact of tunneling rate on the possibility of machine jamming in the squeezing grounds. Simulation results at five reference points on the tunnel circumference along the tunnel or longitudinal displacement profile (LDP) as well as longitudinal contact force profiles (LFP) on both front and rear shields have been examined. Also, maximum thrust force required to overcome friction and drive TBM forward is calculated. This exercise allows for evaluation of the effects of various parameters on convergence and contact forces between the rock and shield, which in turn determines the required propel forces and can define the possibility of machine entrapment.

Soil CO 2 efflux following rotary tillage of a tropical soil

Stopping the increase of atmospheric CO 2 level is an important task and information on how to implement adjustments on tillage practices could help lower soil CO 2 emissions would be helpful. We describe how rotary tiller use on a red latosol affected soil CO 2 efflux. The impact of changing blade rotation speed and rear shield position on soil CO 2 efflux was investigated. Significant differences among treatments were observed up to 10 days after tillage. Cumulative CO 2 efflux was as much as 40% greater when blade rotation of 216 rpm and a lowered rear shield was compared to blade rotation of 122 rpm and raised shield. This preliminary work suggests that adjusting rotary tiller settings could help reduce CO 2 efflux close to that of undisturbed soil, thereby helping to conserve soil carbon in tropical environments.

Forecast analysis of monitoring data for high slopes based on three-dimensional geological information and an intelligent algorithm

In this study, a real-time monitoring system for the interaction between TBM (Tunnel Boring Machine) and surrounding rock is developed, in which the focus is on the cutter-head vibration, and the interaction between the surrounding rock and the shield. The monitoring system consists of sensors, data acquisition subsystem, remote data transmission-storage subsystem and data analysis subsystem. A program is developed to carry out unattended operation of the monitoring software. Further, it can transmit the data synchronously from inside the tunnel to the system outside the tunnel, as well as give feedback information of any operation error to the users automatically. The feasibility, stability, durability of the developed monitoring method has been validated. Subsequently, the time-domain and spectral frequent-domain analysis methods for the accelerated velocity of cutter-head vibration are put forward. Further, the back-calculation analyses method for the surrounding rock pressures acting on the shield and shield jamming warning approach is also developed. Then, the developed monitoring method has been implemented on the double-shield TBM in China’s Lanzhou Water Resource Project. Many evolution rules have been obtained. Firstly, the cutter-head vibration monitoring results show that: (a) the cutter-head vibration is significantly correlated with the TBM advance parameters and the geological conditions; (b) the cutter-head vibrates intensely during TBM restarting after a stoppage or entrapment; (c) the cutter-head vibration intensity increases with the increasing cutter-head rotational speed and penetration rate. Secondly, in-situ monitoring of the surrounding rock pressures acting on the shield manifests that: (a) the surrounding rock pressures acting on the shield is non-uniform, which increase with the growing distance from the tunnel face; (b) the contact scope enlarges from the front shield to the rear shield gradually with time, and the surrounding rock loads acting on the shield increases simultaneously; (c) the squeezing pressures acting on the shield decrease and then return to the relatively small pressures after the relief countermeasures were conducted on the trapped TBM. The measured data give insights on the intense cutter-head vibration warning and shield jamming prediction. Furthermore, the verifications, significances, advantages, weaknesses and future improvements of the monitoring system are discussed.

The Giotto dust impact detection system

The dust impact detection system (DIDSY) comprises six independent subsystems with the primary aim of registering the impacts of all particulates of significant mass incident on the Giotto probe during the post-perihelion encounter with Comet Halley in 1986. Mounted on Giotto's front dust shield, the detectors determine the mass distribution of the dust with a dynamic range of some 16 decades of mass and an ultimate spatial resolution of some 70 km. An additional detector located on the rear shield monitors the dust particles that are able to penetrate the front dust shield. Sensing techniques comprise diaphragm-mounted piezoelectric elements for large and intermediate masses, film capacitance discharge sensors for intermediate masses and impact charge sensors for the smallest masses. They are controlled and the data processed by a microprocessor-based system that allows the wide range of anticipated flux rates to be handled. Measurement principles and sensor characteristics are described.

Physical properties of cometary dust: Relation of DIDSY data to grain properties

The Dust Impact Detection System (DIDSY) for the Giotto Halley Mission consists of two types of sensors for the detection of cometary dust particles: two impact plasma sensors and five piezo-electric momentum sensors. One sensor of each type is covered by a penetration film. A 1 μm thick aluminum film covers an impact plasma sensor. One momentum sensor is mounted onto the rear shield behind the 1 mm front shield made from aluminum. The parameters measured are the total charge released upon impact and the amplitude of the acoustic signal generated by the impact. Both quantities depend on the mass and speed of the impacting particles. At the impact speed of 68 km/sec the mass of cometary dust particles can be determined in the mass range from 10 −17 g to 10 −3 g. From the difference in the countrates measured by the sensors with and without penetration film the average bulk density of dust particles of masses 10 −14 g and 10 −6 g can be determined. With appropriate calibration an accuracy of a factor of 2 for both the mass and density determination can be obtained.