Hard Disk Research Articles

High-Performance Flexible Piezoelectric Nanogenerator Based on Electrospun PVDF-BaTiO3 Nanofibers for Self-Powered Vibration Sensing Applications

In the present era of intelligent electronics and Internet of Things (IoT), the demand for flexible and wearable devices is very high. Here, we have developed a high-output flexible piezoelectric nanogenerator (PENG) based on electrospun poly(vinylidene fluoride) (PVDF)-barium titanate (BaTiO3) (ES PVDF-BT) composite nanofibers with an enhanced electroactive phase. On addition of 10 wt % BaTiO3 nanoparticles, the electroactive β-phase of the PVDF is found to be escalated to ∼91% as a result of the synergistic interfacial interaction between the tetragonal BaTiO3 nanoparticles and the ferroelectric host polymer matrix on electrospinning. The fabricated PENG device delivered an open-circuit voltage of ∼50 V and short-circuit current density of ∼0.312 mA m-2. Also, the PVDF-BT nanofiber-based PENG device showed an output power density of ∼4.07 mW m-2, which is 10 times higher than that of a pristine PVDF nanofiber-based PENG device. Furthermore, the developed PENG has been newly demonstrated for self-powered real-time vibration sensing applications such as for mapping of mechanical vibrations from faulty CPU fans, hard disk drives, and electric sewing machines.

Micromagnetic Simulation of L10-FePt-Based Transition Jitter of Heat-Assisted Magnetic Recording at Ultrahigh Areal Density.

The areal density of hard disk drives increases every year. Increasing the areal density has limitations. Therefore, heat-assisted magnetic recording (HAMR) technology has been the candidate for increasing the areal density. At ultrahigh areal density, the main problem of the magnetic recording process is noise. Transition jitter is noise that affects the read-back signal. Hence, the performance of the magnetic recording process depends on the transition jitter. In this paper, the transition jitter of L10-FePt-based HAMR technology was simulated at the ultrahigh areal density. The micromagnetic simulation was used in the magnetic recording process. The average grain size was 5.1 nm, and the standard deviation was 0.08 nm. The recording simulation format was five tracks in a medium. It was found that a bit length of 9 nm with a track width of 16.5 nm at the areal density of 4.1 Tb/in2 had the lowest transition jitter average of 1.547 nm. In addition, the transition jitter average decreased when increasing the areal density from 4.1 to 8.9 Tb/in2. It was found that the lowest transition jitter average was 1.270 nm at an 8 nm track width and a 9 nm bit length, which achieved an ultrahigh areal density of 8.9 Tb/in2.

Performance Enhancement of SMR-Based Deduplication Systems

Due to the fast-growing amount of data and cost consideration, shingled-magnetic-recording (SMR) drives are developed to provide low-cost and high-capacity data storage by enhancing the areal-density of hard disk drives, and (data) deduplication techniques are getting popular in data-centric applications to reduce the amount of data that need to be stored in storage devices by eliminating the duplicate data chunks. However, directly applying deduplication techniques on SMR drives could significantly decrease the runtime performance of the deduplication system because of the time-consuming SMR space reclamation caused by the sequential write constraint of SMR drives. In this article, an SMR-aware deduplication scheme is proposed to improve the runtime performance of SMR-based deduplication systems with the consideration of the sequential write constraint of SMR drives. Moreover, to bridge the information gap between the deduplication system and the SMR drive, the lifetime information of data chunks is extracted to separate data chunks of different lifetimes in different places of SMR drives, so as to further reduce the SMR space reclamation overhead. A series of experiments was conducted with a set of realistic deduplication workloads. The results show that the proposed scheme can significantly improve the runtime performance of the SMR-based deduplication system with limited system overheads.

Design A Mini Operating System Using Open Source System

Abstract: COSMOS (C# Open Source Managed Operating System) Paper provides a framework and tool-chain to develop an OS purely in managed code (C# and VB .NET). Cosmos supports integration with Visual Studio, and therefore is much easier to use. However, the framework is not rich, and therefore, there is still a lot of work to be done on OS developer side (E.g., it does not support mouse, file system etc.) In this paper, a microkernel based OS is developed using COSMOS framework for x86 based computer systems. This paper demonstrates device driver (PS/2) pointing device and GUI System. Since Cosmos does not provide support file system, mouse, keyboard, we have designed appropriate drivers for screen, mouse and keyboard. We have developed Event handlers and drivers for each device.In this part, we have developed drivers for Hard Disk and RAM to detect them in order to achieve partial fulfilment. From the development of general purpose computers, software industry has also evolved. However, there is not much improvement in OS development, as compared with other fields of software world: while other fields are enjoying power of garbage collection, OS developers are still doing their job in classic languages like C, C++ and assembly. Although there has been some research work regarding this, none of them was successful. This project is an attempt to develop a mini OS in pure managed code, particularly C# and .NET Framework 4.0.

Distributed Activation Energy Modeling and Py-GC/MS Studies on Pyrolysis of Different Printed Circuit Boards for Resource Recovery.

Printed circuit boards (PCBs) constitute an important segment of electronic waste that can be effectively utilized to recover valuable metals and organics. The present work is focused on the kinetics and product distribution from pyrolysis of three different PCB samples, viz., television PCB (TV PCB), motherboard PCB (MB PCB), and hard disk PCB (HD PCB). The PCBs were pretreated to eliminate most of the metallic constituents. Kinetic analysis was performed using Vyazovkin’s isoconversional method and distributed activation energy model (DAEM). The average apparent activation energies obtained from the Vyazovkin method were 207.2, 158.9, and 179.7 kJ mol–1 for the TV PCB, MB PCB, and HD PCB, respectively. The DAEM with five, four, and four pseudo-components was used to describe the decomposition kinetics of the TV PCB, MB PCB, and HD PCB, respectively. Importantly, two types of distributions, viz., Gaussian and Weibull, were utilized to effectively model the nonisothermal data obtained from thermogravimetric analysis at 10 and 20 °C min–1. The evolution of pyrolysates belonging to functional groups such as phenolics, aromatics, aliphatics, halogenated compounds, N-containing compounds, and oxygenates was studied at two different temperatures (500 and 700 °C) using analytical pyrolysis–gas chromatograph/mass spectrometry (Py-GC/MS). The Py-GC/MS results demonstrated an increase in selectivity to aromatics and straight-chain aliphatics at 700 °C with a concomitant decrease in selectivity to phenols and oxygenates.

Performance evaluation of tape library systems

Magnetic tape provides a cost-effective way to retain the exponentially increasing volumes of data being produced. The low cost per gigabyte and the low energy consumption render tape a preferred option over hard disk drives and flash for infrequently accessed data. Assessing the performance of tape library systems is central to achieving appropriate storage provisioning and dimensioning. Performance is affected by the number and the operational characteristics of the tape drives and the robotic arms, and the mount and unmount policies deployed. In this paper, we develop a novel analytical model that accurately captures the principal aspects of tape library operation. Several relevant performance measures including the mean waiting time and the mount/unmount rates are derived. The model provides useful insights into the behavior of the tape libraries and yields results that enable a better understanding of the design tradeoffs. The validity of the model developed is confirmed by demonstrating a good agreement of the predicted performance with that obtained by simulation across various configurations. To mitigate the burden on the robotic mechanism, a scheme of accumulating multiple requests before sending them to the tape library is proposed and studied.

Hyperparameter Optimization on Ensemble Regression Tree for Lip Coloring Simulation

Technology helps us in many activities and keeps growing, so it makes activities more efficient, time-saving, using fewer resources and also information and entertainment are accessible. Machine Learning technology is the fastest-growing field in computer science that is used in many areas such as marketing, healthcare, manufacturing, information security, and transportation. One of the machine learning methods is the Ensemble of Regression Tree (ERT) which has succeeded in detecting facial features on the eyebrows, eyes, nose, and lips. However, utilization ERT method has not been found to detect specific areas such as lips only for gaining optimization. Then this research will be conducted to extract the facial feature annotation dataset from the iBUG 300W dataset with 68 facial features to 20 lip area points. The results of the extraction are reduced error rate, resources saving, lip features still detected and lip coloring simulation was successfully carried out using the configuration of hyperparameter values, tree = 4, regularization = 0.25, cascade = 8, feature pool = 500, oversampling = 40 and translation jitter = 0. From observations also discovered optimization that hard disk resource savings are 69.36%, RAM 30.8%, and CPU 3.8%; reduce the error rate by 0.058%; and increase inference speed by 39%.

Overview of Adhesive Bonding Technology for Nano- and Microsystem Technics

The review focuses on adhesive bonding technology, which is used both for manufacturing various micro- and nanoelectronic devices, sensors and microsystems, and for assembling or integrating various components. Information on the theory of adhesive bonding mechanisms is presented. The properties and applications of four classes of polymers are reviewed: thermoplastic, ther-mosetting, elastomeric, and hybrid. The classification of different mechanisms used to initialize the curing process of adhesives is presented. Existing methods of applying polymers to the wafer surface are described. The main types of designs and principles of operation of adhesive wafer bonding equipment are presented, as well as its main suppliers. Examples of procedures and suitable process parameters are given for both wafer bonding with a continuous layer of adhesive and wafer bonding with patterned adhesive layers (also called selective or local bonding). The conditions required to improve the quality of the adhesive bond and to reduce the density of defects are specified, including cases of bonding wafers made from different materials. Adhesive wafer bonding is used for the fabrication of three-dimensional integrated circuits, and for the integration of integrated circuits with microsystems such as infrared focal plane arrays, spatial light modulators (micromirror arrays), microtip arrays for data storage systems, and laser systems. Adhesive wafer bonding is also used for the fabrication of microcavities in packaging applications, for manufacturing of liquid crystal on silicon (LcoS) components, for thin-film solar cells, for radiofrequency components, for microfuel cells, for hard disk drive microactuators, for the bioMEMS and micrototal analysis systems.

The impact of strength exercises in the opposite double hierarchical style on some abilities in the effectiveness of the hard disk for the class (F40) for men

The importance of the research is reflected in the use of the opposite double hierarchical training method and the design of structural charts as a time indicator for organizational work that depends on the use of weights, rubber ropes and medical balls in different shapes and weights, and through a serious practical attempt to investigate modern training alternatives using strength exercises in this opposite double hierarchical method to achieve Good technical performance and a high level of achievement, and this is one of the necessities of working on how to overcome the stability of the achievement level for the effectiveness of discus throwing for (F40) players with disabilities, because the great progress witnessed in athletics activities is due to the benefit of workers in the field of sports training from following the correct scientific method And good training in order to achieve the goals to be reached, and the research problem was the researchers noticed that the effectiveness of the discus throw for the disabled for the F40 category still suffers from stability in developing results and reaching the best records compared to other countries and other activities.

Regionalized chemical footprint method to identify aquatic ecotoxicity hotspots of hard disk drive rare-earth magnets.

The chemical footprint (ChF), which combines life cycle assessment (LCA) and quantitative risk assessment principles, shows promise for exploring localized toxicity impacts of manufacturing processes, which is not achievable with LCA alone. An updated ChF method was applied to the global annual production of a hard disk drive (HDD) rare-earth element (REE) magnet assembly, assuming a supply chain in East and Southeast Asia. Existing REE magnet assembly LCA inventories were combined with supplier manufacturing locations to create a cradle-to-gate spatial unit process inventory. Emissions from the electricity grid for each manufacturing site were downscaled to hydrobasins of interest using the Global Power Plant Database. The predicted no effect concentration (PNEC) was chosen as the ecotoxicity pollution boundary to determine the threshold for dilution of each chemical of concern (CoC) and to calculate the ChF. Finally, a high-resolution hydrological database provided volumes of the freshwater river reach draining each hydrobasin and was used to calculate the dilution capacity (DC), that is, the volume required to remain at or below the PNEC for each CoC. The total ChF of annual REE magnet assembly production was 6.91E12 m3 , with hotspots in watersheds in China and Thailand where REEs are processed and steel metalworking takes place. Metals were the primary CoCs, with cadmium and chromium(VI) comprising 77% of total ChF. Dilution factors ranged from 5E-09 to 9E + 03 of the DC of the waterbody, reflecting the spatial variability in both emissions and DC. An advanced ChF method was demonstrated for HDD REE magnets. Scoping is a key step required to reduce model complexity. The use of regionalized fate factors and standardized hydrological data sets improves the comparability of ChFs across hydrobasins. Additional work to combine data sets into readily available tools is needed to increase usability and standardization of the ChF method and promote wider adoption. Integr Environ Assess Manag 2023;19:272-283. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Circulation statistics and the mutually excluding behavior of turbulent vortex structures.

The small-scale statistical properties of velocity circulation in classical homogeneous and isotropic turbulent flows are assessed through a modeling framework that brings together the multiplicative cascade and the structural descriptions of turbulence. We find that vortex structures exhibit short-distance repulsive correlations, which is evidenced when they are "tomographically" investigated, by means of planar cuts of the flow, as two-dimensional vortex gases. This phenomenon is suggested from model improvements which allow us to obtain an accurate multiscale description of the intermittent fluctuations of circulation. Its crucial new ingredient, the conjectured hard disk behavior of the effective planar vortices, is then found to be strongly supported from a study of their spatial distributions in direct numerical simulations of the Navier-Stokes equations.

Task allocation and planning for product disassembly with human–robot collaboration

This paper presents a comprehensive disassembly sequence planning (DSP) algorithm in the human–robot collaboration (HRC) setting with consideration of several important factors including limited resources and human workers’ safety. The proposed DSP algorithm is capable of planning and distributing disassembly tasks among the human operator, the robot, and HRC, aiming to minimize the total disassembly time without violating resources and safety constraints. Regarding the resource constraints, we consider one human operator and one robot, and a limited quantity of disassembly tools. Regarding the safety constraints, we consider avoiding potential human injuries from to-be-disassembled components and possible collisions between the human operator and the robot due to the short distance between disassembly tasks. In addition, the transitions for tool changing, the moving between disassembly modules, and the precedence constraint of components to be disassembled are also considered and formulated as constraints in the problem formulation. Both numerical and experimental studies on the disassembly of a used hard disk drive (HDD) have been conducted to validate the proposed algorithm. • Disassembly sequence planning considering human-robot collaboration (HRC) • Consideration of constraints including limited resources and human worker’s safety • Distributing and planning disassembly tasks among human, robot, and HRC • Experimental validation on disassembly of used hard disk drives (video available)

A Study of Three-Dimensional Equalization for Reproducing a Double-Layer Magnetic Recording Medium

To increase the recording density of hard disk drives (HDD), three-dimensional (3-D) magnetic recording with multiple recording layers is attracting much attention as a next-generation recording method. We have reported that the two-dimensional (2-D) partial response maximum likelihood (PRML) can achieve a good BER performance using the PR channel obtained from the differential-phase bit response in the 3-D magnetic recording system with a double recording layer. In this study, we realize the 3-D equalization by the 2-D finite impulse response (FIR) (2-D FIR) filter and 2-D PRML system over two layers and evaluate the 3-D equalization to further increase the recording density. The transfer function of the 2-D PR channels is determined by the response for the in-phase or differential-phase bits in a double-layer magnetic recording medium. The results show that the 2-D PRML channels with 3-D equalization based on the differential-phase transfer function achieve a good bit error rate (BER) performance for system noise.

Multiple Spin Injection Into Coupled Field Generation Layers for Low Current Operation of MAMR Heads

Microwave-assisted magnetic recording (MAMR) is a promising technique for improving the recording density of hard disk drives (HDDs). We propose a spin-torque oscillator (STO) structure with two field generation layers (FGLs) and two spin-injection layers (SILs) for microwave generation. By using a macrospin model and micromagnetic simulations, we numerically demonstrate the low current operation of the STO. The nearly antiparallel oscillations of the FGLs, which make suitable microwave distribution for MAMR, are stabilized by slight modulation of the in-plane phases of the FGLs and synchronization of the SILs. The enlarged spacing between the FGLs enhances the microwave amplitude at the media plane. These results indicate that, by using the dual-SIL dual-FGL STO, write heads for MAMR can operate using little energy to achieve high recording density.

Bit-Flipping Scheme Using K-Means Algorithm for Bit-Patterned Media Recording

As the need for storing significant amounts of data has increased, an increased areal density (AD) of hard disk drives is required. Bit-patterned media recording (BPMR) with the ability to increase AD is regarded as one of the future magnetic storage systems. Reducing the distance between islands storing 1 bit can provide high AD, but it creates problems of intersymbol and intertrack interferences. In this study, we propose a bit-flipping scheme using the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -means algorithm for the BPMR system. In the proposed scheme, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -means algorithm, which is an iterative clustering method for identifying similar samples and assigning them to clusters, is used to assign the samples that consist of the main and neighboring data to clusters. The predicted index from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -means is utilized to compare and flip the sign of the main data when the sign is different. The proposed scheme flips the sign of data that is predicted to be an error and improves the performance using the neighboring information.

Retrieving Forensically Sound Evidence From the ESP Series of IoT Devices

The ESP series of electronics chips and boards are one of the most popular IoT devices and are dominant in the low-end IoT market. Unlike traditional electronic devices, in order to maintain the compact size, ESP devices are not equipped with a hard disk drive. Instead, their microcontrollers are tightly coupled with flash storage chips, which are the high-value targets from a digital forensics (DFs) perspective. To retrieve forensically intact evidences from these devices’ flash storage chips, investigators must be very careful in extracting data, in case the microcontrollers are activated unintentionally, which may allow the microcontroller to write something to the flash storage chips—the result will be unacceptable at court because the data integrity is concerned. This article is trying to solve this challenge, especially for tiny devices, by providing a standard process, utilizing 3D-printed enclosures, spring pins, and cold soldering techniques. The proposals here for the ESP series of IoT devices can be further explored in other IoT devices in the field of DFs.

Wave File Compression Analysis and Implementation using The Huffman Method

One of the sound file formats that are widely used in the Windows operating system is the Wave format (*. WAV). This format is widely used for gaming and multimedia purposes. Wave is actually a raw format where the voice signal is directly recorded and quantized into digital data. The basic format of this file by default does not support compression and is known as PCM (Pulse Code Modulation). If you record a CD Audio quality song using a sampling rate of 44.1 kHz, 16 bits per sample, 2 channels (stereo), then the total media required to store this audio data per second is 176,400 bytes, so for a duration of 1 minute it takes 10,584 MB. If the average duration of one song is 5 minutes, it takes more than 50 MB of space to store the audio data of the song. This is of course very wasteful of storage media such as hard disks even though there are currently large hard disk capacities available.

Molecular hints of two-step transition to convective flow via streamline percolation.

Convection is a key transport phenomenon important in many different areas, from hydrodynamics and ocean circulation to planetary atmospheres or stellar physics. However, its microscopic understanding still remains challenging. Here we numerically investigate the onset of convective flow in a compressible (non-Oberbeck-Boussinesq) hard disk fluid under a temperature gradient in a gravitational field. We uncover a surprising two-step transition scenario with two different critical temperatures. When the bottom plate temperature reaches a first threshold, convection kicks in (as shown by a structured velocity field) but gravity results in hindered heat transport as compared to the gravity-free case. It is at a second (higher) temperature that a percolation transition of advection zones connecting the hot and cold plates triggers efficient convective heat transport. Interestingly, this picture for the convection instability opens the door to unknown piecewise-continuous solutions to the Navier-Stokes equations.

Fast DNA encoding algorithm inspired by the SPOOLing system.

The digital images are widely used in many fields, such as the military, government, and traffic. DNA encoding, as an important means of image encryption, has received increasing attention due to its powerful parallelism. But its low coding efficiency limits its application. This paper designs a quartering search method and proposes a fast DNA encoding algorithm inspired by the simultaneous peripheral operations online system. By trading off memory for time, the base combinations corresponding to 256 different pixel values are precomputed and prestored in the computer memory or hard disk in advance. When the corresponding DNA encoding or decoding operations are carried out, the data can be called to avoid a large number of repeated calculations. Experimental results and comparative analyses show that the proposed algorithm can greatly improve the efficiency of DNA encoding or decoding and be practical. Our algorithm can further facilitate the promotion and application of DNA encoding in the field of image encryption.

Shingled Magnetic Recording (SMR) and Two-Dimensional Magnetic Recording (TDMR)

Data areal-density has always been a key metric in magnetic recording. An increase in ‘bits per square inch’ allows a higher capacity product to be developed at similar cost. Areal densities have grown at rates as high as 100% per year, but by 2010 these rates had dropped to more like 10%. In response to this slowdown, numerous other avenues were explored including increasing the number of disks in the form factor - an opportunity enabled by the advent of helium-filled drives. Alongside such mechanical improvements, two important innovations were made in the physical recording processes. These innovations were Shingled Magnetic Recording (SMR) and Two Dimensional Magnetic Recording (TDMR). SMR was developed as a response to the difficulty of maintaining fields while writing very narrow tracks with a conventional magnetic head. By keeping the head relatively wide, the field could be kept strong and by overlapping the written tracks, the final track pitch could be reduced. Two Dimensional Magnetic Recording (TDMR) was developed recognizing that increases in track density were also limited by the interference between tracks. By reading back the wanted track(s) with several closely-spaced sensors, the effects of the interference could be greatly mitigated. Both SMR and TDMR are now widely deployed in modern hard disk drives although neither realized the gains originally anticipated.