Two-disk System Research Articles

Low gain avalanche detectors for precision timing in the CMS MTD endcap timing layer

The MIP Timing Detector (MTD) of the Compact Muon Solenoid (CMS) is designed to provide precision timing information (with resolution of ∼40 ps per layer) for charged particles, with hermetic coverage up to a pseudo-rapidity of |η| = 3. This upgrade will reduce the effects of pile-up expected under the High-Luminosity LHC running conditions and brings new and unique capabilities to the CMS detector. The time information assigned to each track will enable the use of 4D reconstruction algorithms and will further discriminate in the time domain interaction vertices within the same bunch crossing to recover the track purity of vertices in current LHC conditions. The endcap region of the MTD, called the Endcap Timing Layer (ETL) will be instrumented with silicon-based low gain avalanche detectors (LGADs), covering the high radiation pseudo-rapidity region between |η| = 1.6 and 3.0. Each endcap will be instrumented with a two-disk system of LGADs, read out by Endcap Timing Readout Chips (ETROCs), being designed for precision timing measurements. We will present an overview of the MTD ETL design, which is detailed in the MTD technical design report. We will also present the R&D and test beam studies that were instrumental for achieving the ETL design, characterization of the LGAD sensors, as well as recent progress on the development of the ETROC readout electronics.

Investigation of wheel squeal noise under mode coupling using two-disk testrig experiments

Wheel squeal noise is a common problem that occurs in railway systems especially on curved tracks. These tonal noises are usually found at high frequency, typically over 1 kHz. The cause of the squeal noise remains unclear and could be different under varied conditions. Several mechanisms that could cause wheel squeal, including falling friction and mode coupling, have been proposed in literature. Most existing lab experimental investigations were focused on the squeal noise caused by falling friction with vertical contacts. As a result, the squeal noise generated by mode coupling could be missed due to the absence of a non-vertical contact angle. In this work, a two-wheel test rig has been designed with curved wheel profiles to achieve adjustable contact angles with lateral components. Experimental and numerical modal analysis of the two-disk system was conducted to determine the dynamic characteristics for exploration of mode coupling effects. Using a set of benchmark parameters predicted to be the cause of significant mode-coupled instability, squeal noise was found at frequencies higher than the existing falling friction experimental tests as reported in the literature. The frequency and amplitude measured in the experiments agreed with the predictions of the analytical mode coupling model. Further experiments varying control parameters, contact angle, angle of attack and direction of rotation were performed, confirming that the new squeal noise was caused by mode coupling.

A novel ANN-based four-dimensional two-disk hyperchaotic dynamical system, bifurcation analysis, circuit realisation and FPGA-based TRNG implementation

This paper describes the modelling, bifurcation analysis, circuit realisation and FPGA implementation of a novel ANN-based four-dimensional two-disk dynamical system exhibiting hyperchaos and hidden attractor. This paper provides a detailed analysis of the multistability, coexisting attractors and bifurcation properties of the novel two-disk dynamical system with hyperchaos. The novel two-disk dynamical system does not possess any rest point pinpointing the presence of hidden hyperchaotic attractor. We realise the dynamic equations of the two-disk hyperchaotic dynamical system with a real circuit. Next, we build design and implementation of ANN-based two-disk hyperchaotic dynamical system on FPGA. Finally, using FPGA-based implementation of the two-disk hyperchaotic dynamical system, we design and implement a novel high-speed True Random Number Generator (TRNG).

Vibrational Interaction of Two Rotors with Friction Coupling

A lumped parameter model is presented for studying the dynamic interaction between two disks in relative rotational motion and in friction contact. The contact elastic and dissipative characteristics are represented by equivalent stiffness and damping coefficient in the axial as well as torsional direction. The formulation accounts for the coupling between the axial and angular motions by viewing the contact normal force a result of axial behavior of the system. The model is used to investigate stick-slip behavior of a two-disk friction system. In this effort the friction coefficient is represented as an exponentially decaying function of relative angular velocity, varying from its static value at zero relative velocity to its kinetic value at very high velocities. This investigation results in the establishment of critical curve defining two-parameter regions: one in which stick-slip occurs and that in which stick-slip does not occur. Moreover, the onset and termination of stick-slip, when it occurs, are related to the highest component frequency in the system. It is found that stick-slip starts at a period nearly equal to that of the highest component frequency and terminates at a period almost three times that of the highest component frequency.

Improvement of slider off-track vibration through design parameter modifications of a compatible FDB spindle system

Recently, the hard disk drive (HDD) industry has tried to use a compatible spindle system regardless of the number of disks because of the resulting cost reduction and standardization of components. The center of gravity (CG) location predominantly affects the disk and slider off-track vibration, which is why the rocking mode of a spindle system is affected by the CG. Any changes to the CG affect the operational vibration of the spindle system. In a compatible fluid dynamic bearing (FDB) spindle system, changing the number of disks may alter the CG. Nevertheless, research into the compatibility of FDB designs has not been undertaken. In this study, FDB design parameters were selected to reduce the slider off-track vibration with variations in the CG considering a compatible spindle system. First, a verified finite element (FE) model of a spindle system was constructed. The amplitude and frequency of the rocking mode were compared between a one-disk spindle system and a two-disk spindle system using the FE model, considering the relationship between the CG location, which is changed by the number of disks, and the location of the upper and lower journal bearings. HDD prototypes were then manufactured using the improved design. Based on the manufactured spindle system, the variations in the rocking mode characteristics and slider off-track vibration were measured and operational vibration tests were performed to verify the effect of the number of disks on the slider off-track vibration. An improved FDB spindle design was developed with a reduced rocking mode, and a compatible spindle system was proposed.

A Non-Phenomenological Account of Friction/Vibration Interaction in Rotary Systems

Using a nonlinear model of a two disk brake system, coupled equations of motion are found for their frictional interaction. The mathematical formulation relates the tribological events at micron scale and the macroscopic scale vibration response of a two-disk brake system. This is accomplished by a viscoelastic account of interaction at the micron scale, its statistical quantification through the approximate analytical representation of the statistical expectation of contact force and the introduction of the contact force into the macroscale dynamics of the two-disk system. Steady-state analysis of the system establishes the relation between friction torque and speed and supports observed behavior of many mechanical systems with friction. It is shown that, as a result of coupling of the macrosystem’s dynamics and contact, there are combinations of parameters at the micro- and macroscale that yield negative slope in friction torque/sliding speed relation, a well known source of dynamic instability. This results in an effective negative damping that tends to decrease with decrease in the normal load and/or increase in structural damping of the system.

A Study of the Effects of Motion on Mass Transfer in Pits in a Two-Disk Hydrodynamic System

Effects of medium motion on the mass transfer in model pits in a two-disk hydrodynamic system are studied. Steel 12Х18Н10Т in sodium chloride solutions at 293 to 333 K was an object of the study. The dependences obtained allow evaluating the effects of medium motion on mass transfer in a model pit, depending on its geometrical parameters.

Using rank hashing function to develop a data allocating scheme for a two-disk system

A new algorithm for distributing a set of multiattribute records onto a two-disk system is presented. The rank hashing allocation has been used to develop this new algorithm. We show that the new scheme can achieve the strictly optimal efficiency for partial match queries and all records can be allocated properly into a two-disk system. A simulation experiment was carried out; results are compared with conventioned methods. Based on the average response time, the performance of the new scheme is better than that of the two conventional methods.

Elastic particle scattering from two hard disks

In a scattering problem where an incoming particle interacts elastically with more than one scatterer the trajectories that the particle can follow can be quite complex, even in two dimensions. In this paper the elastic scattering of a particle from a two-disk system is solved explicitly. This is a nontrivial problem that can serve to introduce the concepts needed to understand more complex systems of three or more disks, which defy an explicit analytic treatment. Indeed, a target of more than two disks of equal radius leads to behavior that has recently been termed chaotic scattering.

On the design of multiple key hashing files for concurrent orthogonal range retrieval between two disks

This paper concerns the following problem: given a set of multi-attribute records, a fixed number of buckets and a two-disk system, arrange the records into the buckets and then store the buckets between the disks in such a way that, over all possible orthogonal range queries (ORQs), the disk access concurrency is maximized. We shall adopt the multiple key hashing (MKH) method for arranging records into buckets and use the disk modulo (DM) allocation method for storing buckets onto disks. Since the DM allocation method has been shown to be superior to any other allocation methods for allocating an MKH file onto a two-disk system for answering ORQs, the real issue is knowing how to determine an optimal way for organizing the records into buckets based upon the MKH concept. A performance formula that can be used to evaluate the average response time, over all possible ORQs, of an MKH file in a two-disk system using the DM allocation method is first presented. Based upon this formula, it is shown that our design problem is related to a notoriously difficult problem, namely the Prime Number Problem. Then a performance lower bound and an efficient algorithm for designing optimal MKH files in certain cases are presented. It is pointed out that in some cases the optimal MKH file for ORQs in a two-disk system using the DM allocation method is identical to the optimal MKH file for ORQs in a single-disk system and the optimal average response time in a two-disk system is slightly greater than one half of that in a single-disk system.

Influence of a contact region in a frictional surface on squeal in electromagnetic friction clutches and brakes.

A squeal phenomenon in an electromagnetic clutch depends not only on time-independent factors (shape and size, natural frequencies and damping ratios of a rotor and an armature) but also on variable factors (a contact region and a contact position). In this paper, the stability of a two-disk system modeled after a practical clutch is discussed theoretically. Numerical calculations based on this squeal theory show the influence of a contact region and a contact position on the squeal : (1) the fourth mode squeal is generated when an armature is in contact with the outer pole of a rotor ; (2) the lower mode squeal is generated when the armature is in contact with the outer part of the facing surface of the rotor ; (3) no squeal is generated when the armature is in contact with the entire facing surface or with the inner pole of the rotor.

Performance of two-disk partition data allocations

In this paper, we present a method, called the partition data allocation method, to allocate a set of data into a multi-disk system. Using the partition data allocation method, we shall show that, in a two-disk system, the performance is influenced by how we disperse similar data onto different disks.

Primary plate identification of group A beta-hemolytic streptococci utilizing a two-disk technique

A two-disk system is described which allows primary plate identification of group A beta-hemolytic streptococci. Group A beta-hemolytic streptococci could be visualized on primary throat culture plates by using trimethoprim-sulfamethoxazole to inhibit normal flora. In the heavily inoculated area of Trypticase soy agar plates containing 5% sheep blood, a 25-microgram/ml trimethoprim-sulfamethoxazole disk was placed contiguous to a 0.04-U bacitracin disk. A total of 259 throat specimens were examined with this two-disk system. The swabs from these throat specimens were incubated in Todd-Hewitt broth. The bacterial pellet from the broths was stained by fluorescent antibody as a control. Of the cultures that were determined to be positive on the plates, 75% could be read unequivocally after overnight incubation, whereas the remaining 25% required subculture. The plates recovered 91% of the cultures which were considered as true positives by the broth-fluorescent-antibody technique. This method provided a significant savings in time compared with standard plate methods and in cost of materials compared with broth-fluorescent-antibody methods. This technique is particularly valuable for producing rapid results in laboratories where fluorescence microscopy would not be cost-effective.

Use of the disk file on stretch

The paper begins by briefly describing the Stretch (IBM 7030) computer with special emphasis given to the organization and operation of its input-output equipment. Physical characteristics of the two-disk system (4,194,304 72-bit words, 8 µ sec-per-word transmission rate, etc.) are noted. Timing limitations due to arm motion and disk rotation are discussed. Applications of disk usage are discussed separately for problem programs and for systems programs such as compilers and the supervisory program. Approximately 260,000 words of disk storage are reserved for the storage of systems programs and the subroutine library. Problem programs, however, are not currently filed on the disk. Certain programming techniques are discussed for transmitting words between disk and core storage with minimum delaying and interruption of the arithmetic unit. Dumps on disk are considered for both recovery from computer malfunction and for mathematical or physical developments during the calculation.