Roll Off Research Articles

A feasibility study of introducing chin straps of safety helmets as a statutory requirement in Hong Kong construction industry

Safety helmets contribute to the protection of head and wearing it is a statutory requirement in Hong Kong construction sites. However, there is a lack of secured system between the helmet and head which caused rolling off of helmet in few circumstances. A chin strap has a design function that secures the head and helmet in order to prevent it from rolling off. This paper aims to identify the current usage, safety performance and negative impact of using chin straps on safety helmets in the Hong Kong construction industry. It is found that effectively using chin straps can secure the helmets onto head and prevent it from rolling off. However, retractable chin straps brought greater discomfort to the workers than adjustable chin straps. It is also figured out when workers did not wear chin straps, there are few circumstances that will cause the helmets to roll off such as heading up/down, windy condition and slight impact. The most significant finding is that there is inadequate knowledge and cognition for workers who did not wear chin straps. It is thus necessary for the relevant government departments to revise the statutory requirements on safety helmets. Construction companies should also encourage the workers to use chin straps so that the safety performance of construction industry can be improved.

シリコンウェーハ研磨加工におけるウェーハエッジ部の表面形状創成過程

Design specifications of semiconductor devices are constantly being miniaturized for increasing the integration density of the devices, which requires highly flat surfaces of silicon wafers as the starting materials of the devices. However, surface flatness significantly deteriorates near the wafer edge because of edge roll off during polishing as the final stage of the wafer manufacturing process. To address this problem, various polishing methods such as the use of polishing pads with small deformation property have been conducted and, however, cannot meet the recent demand for diminishing edge roll off in small stock removal of 10μm or less. In this study, the influence of polishing pad property such as deformation property on obtained edge surface flatness was experimentally investigated in various stock removal, and the influence on the stress distribution near the wafer edge was investigated using finite element methods. Based on the results, thin polishing pads with large deformation property were developed. Polishing experiments on silicon wafers showed that the developed polishing pads achieved high surface flatness near the edge in the overall progress of polishing including small stock removal as compared to commercial pads.

Evaluation of Polishing Pad Property by Rubber Hardness Test-estimating Edge Surface Flatness of Workpiece

Demand for diminishing edge roll off of workpiece has rapidly increased, particularly in polishing silicon wafers as the substrates of the semiconductor devices and glass disks as the substrates of magnetic media disks. In general, the usage of harder polishing pads is thought to be very effective in achieving the high surface flatness of the workpiece edge. Then the hardness, especially the rubber hardness of the polishing pads is widely measured as one of the most important pad specifications in practical processes. However, it has not been clarified whether the edge surface flatness can be estimated by the current rubber hardness tests. Then, based on the elastic contact theory, the polishing pad property which influences the surface profile near the edge was investigated and, as a result, it was found that the usage of the indenter with a diameter of 20mm or above could estimate the obtained edge surface flatness appropriately in indentation tests such as rubber hardness tests.

Audio Denoising, Recognition and Retrieval by Using Feature Vectors

In this paper, we present the study of audio signal denoising, recognizing its audio type and retrieving similar signals from the database. Primarily the signal is denoised to remove any noise present in the unknown signal. Time Frequency Block Thresholding is used to achieve this. Removing the noise from audio signals requires processing of time-frequency coefficients in order to keep away from producing the musical noise. A block thresholding estimation procedure is introduced, which relates the parameters adaptively to signal property. Content Based Audio Retrieval system is very useful to identify the unknown audio signals. Audio signals are classified into music, speech and background sounds. This is done by the use of various feature vectors such as zero crossing rate, spectral centroid, spectral flux, spectral roll off. Use of multiple feature vectors improves the accuracy of the results being retrieved from the audio database. Various experiments demonstrate the performance and accurateness, providing good results for non standard signals.

A 3-D Miniaturized High Selectivity Bandpass Filter in LTCC Technology

Transmission zeros are used to improve the roll-off factors of filters but as a consequence, the out-of-band rejection decreases. In this work, an LTCC filter design is presented which employs a series inductor (implemented as a via hole) to improve the out-of-band rejection by introducing a third transmission zero. The filter, designed for GPS band (1.57 GHz), has one of the smallest reported foot prints ( (0.063×0.048×0.005)λg) and demonstrates the highest roll off factor (16.7 dB/100 MHz) for this band. With only four LTCC layers, the design is cost effective and thus highly suitable for miniaturized, ultra-thin system-on-package applications.

Concatenated Coding in OFDM for Wimax Using USRP N210 and GNU Radio

A software Defined Radio (SDR) device employs a reconfigurable hardware (Universal Software Radio Peripheral-USRP) that may be programmed over-the-air or software (GNU Radio) to function under different Wireless standards. This paper analyzes the effect of various parameters such as channel noise, frequency offset, timing offset, timing beta, FLL (Frequency Lock Loop) bandwidth, Costas loop (phase) bandwidth, filter roll off factor and multiply const on OFDM signal in WiMAX physical layer with concatenated coding using SDR test bed. Concatenated coding is performed by suggesting RM coder and Convolutional coders as inner code and outer codes respectively. Moreover, bit error rate and symbol error rates performance are analyzed by varying bits per symbol, window size and modulation scheme. Results proved that BER and SER values are improved as modulation scheme size (M) is increased. OFDM signal transmission and reception is performed using USRP N210 and configured by GNU radio in the laboratory environment.

Superhydrophobic New Zealand leaves: contact angle and drop impact experiments

Dynamic wetting of the adaxial leaf surfaces of several New Zealand native plants has been studied using water drops, contact angle measurements and drop impact experiments. Three native plants (Arthropodium bifurcatum, Euphorbia glauca and Veronica albicans) are identified as superhydrophobic, having advancing contact angles >160°, with <12° hysteresis and <10° roll off angle. These data are comparable to leaves of the lotus (Nelumbo nucifera), an international superhydrophobicity benchmark. Scanning electron microscopy reveals a range of epidermal microstructures and submicron epicuticle wax textures on native leaves, including superhydrophobic microstructures that are similar to those found on exotic leaves. Drop impacts on N. nucifera, A. bifurcatum and E. glauca were filmed using a high speed camera at Weber number between 15 and 200. Drops impacting on the two native plants exhibited asymmetry due to vascular bundles on the leaf surfaces. Biomimicry and dynamic wetting are important for development of industrial superhydrophobic surfaces.

Single-Mode, High-Speed, and High-Power Vertical-Cavity Surface-Emitting Lasers at 850 nm for Short to Medium Reach (2 km) Optical Interconnects

The vertical-cavity surface-emitting lasers (VCSELs) with high single-mode (narrow linewidth) output power are essential to minimize chromatic dispersion and to further improve the bit-rate distance product in a multimode fiber, which has a significant propagation loss (~3.5 dB/km) at 850 nm wavelength. Here, we demonstrate the detailed design considerations and fabrication of a single-mode, high-power, and high-speed VCSELs at the 850 nm wavelength with oxide-relief and Zn-diffusion apertures for the application of short (0.3 km) to medium reach (2 km) optical interconnects. By optimizing the relative geometric sizes between two such apertures in our demonstrated 850-nm VCSELs, we can not only attain high single-mode output power (~6.5 mW), but also with a reasonable threshold current (<; 2.0 mA). Furthermore, the spatial hole burning effect induced low-frequency roll off can also be minimized in our optimized structure to obtain a maximum data rate up to 26 Gbit/s. The record-high bit rate-distance products for OM4 MMF transmission under ON-OFF keying (14 Gbit/s × 2.0 km) modulation formats have been successfully demonstrated by the use of our VCSEL.

Onboard Fire Safety Assessment Standards for Indonesian Non Convention Roll On Roll Off Passenger Ferries

Roll on roll off passenger ferries play very important role in connecting Indonesia’s more than 17,000 islands. Since these ferries are categorized as ‘Non-convention’ vessels they are not mandatory to comply with international regulations, therefore they are very vulnerable to accidents including fire accident. The study was carried out to establish onboard fire safety assessment standards for Roll on roll off ferries operating on Indonesian waters to be used as guidance for authorities and operators to assess and to ensure the safety of the ferries. The assessment standards are focused on three accident sources include: the vessel; people on board; and the cargo. The standards are derived from fire hazards and their potential risk levels, which are categoriesed as intolerable; tolerable; and negligible. Refer to the risk levels obtained realistic and appropriate actions could then be implemented to prevent the ferries from fire accidents.

Fog-Harvesting Potential of Lubricant-Impregnated Electrospun Nanomats

Hydrophobic PVDF-HFP nanowebs were fabricated by a facile electrospinning method and proposed for harvesting fog from the atmosphere. A strong adhesive force between the surface and a water droplet has been observed, which resists the water being shed from the surface. The water droplets on the inhomogeneous nanomats showed high contact angle hysteresis. The impregnation of nanomats with lubricants (total quartz oil and Krytox 1506) decreased the contact angle hysteresis and hence improved the roll off of water droplets on the nanomat surface. It was found that water droplets of 5 μL size (diameter = 2.1 mm) and larger roll down on an oil-impregnated surface, held vertically, compared to 38 μL (diameter = 4.2 mm) on a plain nanoweb. The contact angle hysteresis decreased from ~95 to ~23° with the Krytox 1506 impregnation.

Fabrication of Super-Hydrophobic Microchannels via Strain-Recovery Deformations of Polystyrene and Oxygen Reactive Ion Etch

In this article, we report a simple approach to generate micropillars (whose top portions are covered by sub-micron wrinkles) on the inner surfaces of polystyrene (PS) microchannels, as well as on the top surface of the PS substrate, based on strain-recovery deformations of the PS and oxygen reactive ion etch (ORIE). Using this approach, two types of micropillar-covered microchannels are fabricated. Their widths range from 118 μm to 132 μm, depths vary from 40 μm to 44 μm, and the inclined angles of their sidewalls are from 53° to 64°. The micropillars enable these microchannels to have super-hydrophobic properties. The contact angles observed on the channel-structured surfaces are above 162°, and the tilt angles to make water drops roll off from these channel-structured substrates can be as small as 1°.

Unaccompanied transport as a strategy for international road hauliers in Ro-Ro short sea shipping

As a consequence of the problems of sustainability caused by the growth of road transport, short sea shipping (SSS) has attracted much attention from the European Union in recent years. Road hauliers, as clients of shipping companies, constitute a key player in the development of SSS. For these firms, the use of this transport mode implies a change to their traditional all-road transport operations. Consequently, if these firms want to maintain stable operations in the SSS context, they need to face the challenge of modifying their profile and adopt an appropriate organisational structure. The aim of this article is twofold: first, to analyse, in the context of roll on-roll off SSS, the two possible operating strategies for road transport firms: accompanied versus unaccompanied transport, in an attempt to determine their characteristics and the factors that condition their use; and second, to analyse the challenges facing international hauliers by changing the process from the all-road transport option to the use of unaccompanied transport in SSS operations, and how these challenges are addressed. A study is made of five international road hauliers that have adapted to become intermodal transport operators. Our findings reveal five key areas for change: organisation of haulage and fleet restructuring, restructuring of driving staff, changes in the operating model and development of coordination capabilities, improving the commercial capacity at destination, and establishing an adequate infrastructure to organise haulage in the destination country. Proper management of the adjustment process largely determines the success of road hauliers in the use of unaccompanied SSS.

Fabrication and Electrowetting Properties of Poly Si Nanostructure Based Superhydrophobic Platform

Poly-silicon based superhydrophobic surface (water contact angle >150°) is being fabricated and its electrowetting properties have been studied. The polysilicon thin film has been deposited over patterned gold electrodes. The polysilicon film is structured to form nanoscale features using Reactive Ion Etching. A thin film of HfO2 high k-dielectric is deposited over the structured polysilicon surface. The surface was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane (PFOS). Such a surface showed Superhydrophobic behavior with water contact angle of 172° and roll off angle <3°. The electrowetting properties of the fabricated device was studied by applying a DC voltage between the gold electrode and the droplet. The electrowetting commences when the applied voltage was 18 V and the contact angle is reduced to 152°. As the applied voltage was increased there was decrease in contact angles.

Under-water superoleophobic glass: unexplored role of the surfactant-rich solvent.

Preparing low energy liquid-repellant surfaces (superhydrophobic or superoleophobic) have attracted tremendous attention of late. In all these studies, the necessary liquid repellency is achieved by irreversible micro-nano texturing of the surfaces. Here we show for the first time that a glass surface, placed under water, can be made superoleophobic (with unprecedented contact angles close to 180 degrees and roll off angles only a few fractions of 1 degree) by merely changing the surfactant content of the water medium in which the oil (immiscible in water) has been dispersed. Therefore, we propose a paradigm shift in efforts to achieve liquid-repellant systems, namely, altering the solvent characteristics instead of engineering the surfaces. The effect occurs for a surfactant concentration much larger than the critical micelle concentration, and is associated to strong adsorption of surfactant molecules at the solid surface, triggering an extremely stable Cassie-Baxter like conformation of the oil droplets.

Low roll off radiation efficiency of charge transfer state excitons based on organic photovoltaic and electroluminescent integrated device

Organic photovoltaic and electroluminescent (EL) integrated devices were fabricated with a heterojunction structure consisting of Rubrene electron donor and fullerene electron acceptor. By using infrared transmission filter and near infrared detector, the ELCT signals of charge transfer state (CTS) excitons were separated from the light emission of singlet (ELSE) or triplet exciton. The EL external quantum efficiencies from pure CTS excitons exhibited ultra-low roll off characteristics. Meanwhile, an improved exponential model was proposed to accurately simulate the relationship between the light emission photons of CTS and singlet excitons versus applied bias, which illuminated the roll off of ELCT and ELSE.

A Three-stage 3.1-10.6 GHz Low-noise Amplifier with High and Flat Gain, Consuming 3.7 mw power from a 1.8 V Supply Using Triple Coordination Technique

A 3.1 to 10.6 GHz low-noise amplifier (LNA) in 0.18 μm technology is presented in this paper. The proposed LNA is implemented in a three-stage structure, including a current reusing cascode structure, a middle stage which compensates gain roll off in middle band and a buffer stage. The low-power dissipation of the design along with the high and flat gain provides a very appropriate combination in ultrawideband frequency design. The designed LNA achieves an average gain of 20 dB and a noise figure less than 2. The power consumption of the design is 3.7 mw.

Experimental Study of Vibrations of Gerbil Tympanic Membrane with Closed Middle Ear Cavity

The purpose of the present work is to investigate the spatial vibration pattern of the gerbil tympanic membrane (TM) as a function of frequency. In vivo vibration measurements were done at several locations on the pars flaccida and pars tensa, and along the manubrium, on surgically exposed gerbil TMs with closed middle ear cavities. A laser Doppler vibrometer was used to measure motions in response to audio frequency sine sweeps in the ear canal. Data are presented for two different pars flaccida conditions: naturally flat and retracted into the middle ear cavity. Resonance of the flat pars flaccida causes a minimum and a shallow maximum in the displacement magnitude of the manubrium and pars tensa at low frequencies. Compared with a flat pars flaccida, a retracted pars flaccida has much lower displacement magnitudes at low frequencies and does not affect the responses of the other points. All manubrial and pars tensa points show a broad resonance in the range of 1.6 to 2kHz. Above this resonance, the displacement magnitudes of manubrial points, including the umbo, roll off with substantial irregularities. The manubrial points show an increasing displacement magnitude from the lateral process toward the umbo. Above 5kHz, phase differences between points along the manubrium start to become more evident, which may indicate flexing of the tip of the manubrium or a change in the vibration mode of the malleus. At low frequencies, points on the posterior side of the pars tensa tend to show larger displacements than those on the anterior side. The simple low-frequency vibration pattern of the pars tensa becomes more complex at higher frequencies, with the breakup occurring at between 1.8 and 2.8kHz. These observations will be important for the development and validation of middle ear finite-element models for the gerbil.

Verification of Icephobic/Anti-icing Properties of a Superhydrophobic Surface

Four aluminum surfaces with wettability varied from superhydrophilic to superhydrophobic were prepared by combining an etching and a coating process. The surface wettability was checked in terms of water contact angle (CA) and sliding angle (SA) under different humidity at -10 °C. High-speed photography was applied to study water droplet impact dynamics on these surfaces. It was found that single and successive water droplets could rebound on the superhydrophobic surface and roll off at a tilt angle larger than 30° under an extremely condensing weather condition (-10 °C and relative humidity of 85-90%). In addition, the superhydrophobic surface showed a strong icephobic property, the ice adhesion on this surface was only 13% of that on the superhydrophilic surface, though they had a similar nano/microtopological structure. Moreover, this superhydrophobic surface displayed an excellent durability of the icephobic property. The ice adhesion only increased to 20% and 16% of that on the superhydrophobic surface after the surface was undergone 20 icing/ice-breaking cycles and 40 icing/ice-melting cycles, respectively. Surface profile and XPS studies on these surfaces indicated a minor damage of the surface nano/microstructure and the coating layer upon these multiple ice-breaking and ice-melting processes. Therefore, this superhydrophobic surface could be a good candidate for icephobic applications.

Flat Feet, Happy Feet? Comparison of the Dynamic Plantar Pressure Distribution and Static Medial Foot Geometry between Malawian and Dutch Adults

In contrast to western countries, foot complaints are rare in Africa. This is remarkable, as many African adults walk many hours each day, often barefoot or with worn-out shoes. The reason why Africans can withstand such loading without developing foot complaints might be related to the way the foot is loaded. Therefore, static foot geometry and dynamic plantar pressure distribution of 77 adults from Malawi were compared to 77 adults from the Netherlands. None of the subjects had a history of foot complaints. The plantar pressure pattern as well as the Arch Index (AI) and the trajectory of the center of pressure during the stance phase were calculated and compared between both groups. Standardized pictures were taken from the feet to assess the height of the Medial Longitudinal Arch (MLA). We found that Malawian adults: (1) loaded the midfoot for a longer and the forefoot for a shorter period during roll off, (2) had significantly lower plantar pressures under the heel and a part of the forefoot, and (3) had a larger AI and a lower MLA compared to the Dutch. These findings demonstrate that differences in static foot geometry, foot loading, and roll off technique exist between the two groups. The advantage of the foot loading pattern as shown by the Malawian group is that the plantar pressure is distributed more equally over the foot. This might prevent foot complaints.

Superhydrophobic Hybrid Inorganic–Organic Thiol-ene Surfaces Fabricated via Spray-Deposition and Photopolymerization

We report a simple and versatile method for the fabrication of superhydrophobic inorganic-organic thiol-ene coatings via sequential spray-deposition and photopolymerization under ambient conditions. The coatings are obtained by spray-deposition of UV-curable hybrid inorganic-organic thiol-ene resins consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), triallyl isocyanurate (TTT), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles. The spray-deposition process and nanoparticle agglomeration/dispersion provide surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior, dependent on the concentration of TMTVSi and hydrophobic silica nanoparticles, can be varied over a broad range to ultimately provide coatings with high static water contact angles (>150°), low contact angle hysteresis, and low roll off angles (<5°). The cross-linked thiol-ene coatings are solvent resistant, stable at low and high pH, and maintain superhydrophobic wetting behavior after extended exposure to elevated temperatures. We demonstrate the versatility of the spray-deposition and UV-cure process on a variety of substrate surfaces including glass, paper, stone, and cotton fabric.