Small Unit Size Research Articles

Conformal polishing of a glass microlens array through oxyhydrogen flame-induced viscoelasticity flow at nano/microscale

Glass microlens arrays with small unit sizes and high integration capacities are widely utilized in various optical systems, but the femtosecond laser milling produces microscale residual steps and nanoscale rough topography on microlens surface. Accordingly, an oxyhydrogen flame polishing is proposed after femtosecond laser milling, aiming to efficiently fabricate the ultrasmooth surface without damaging shape accuracy by triggering a viscoelasticity flow at nano/microscale. Through simultaneous modelling of the polishing process, a large thermal power results in a high viscoelasticity flow velocity for nanoscale topography smoothing, followed by microscale step melting. Then, a single-point polishing experiment is conducted to determine the critical transition temperatures for nanoscale smoothing and microscale melting. It is further experimentally applied to achieve an ultrasmooth surface of cylindrical microlens array with its roughness less than 0.2 nm and no hydroxyl introduction. This process also effectively repairs subsurface damage and reduces the form error to ±0.5 μm, improving the surface quality and shape accuracy. Similar results are also observed for the polishing of spherical microlenses. In conclusion, the method of combining femtosecond laser milling and oxyhydrogen flame polishing holds promise for high-efficiency and high-quality fabrication of glass components with micro features.

CLUSTER FAST DOUBLE BOOTSTRAP APPROACH WITH RANDOM EFFECT SPATIAL MODELING

Panel data is a combination of cross-sectional and time series data. Spatial panel analysis is an analysis to obtain information based on observations affected by the space or location effects. The effect of location effects on spatial analysis is presented in the form of weighting. The use of panel data in spatial regression provides a number of advantages, however, the spatial dependence test and parameter estimators generated in the spatial regression of data panel will be inaccurate when applied to areas with a small number of spatial units. One method to overcome the problem of small spatial unit size is the bootstrap method. This study used the fast double bootstrap (FDB) method by modeling the poverty rate in the Flores islands. The data used in the study was sourced from the BPS NTT Province website. The results of Hausman test show that the right model is Random effect. The spatial dependence test concludes that there is a spatial dependence and the poverty modeling in the Flores islands tends to use the SAR model. SAR random effect model R2 shows the value of 77.38 percent and it does not meet the assumption of normality. Spatial Autoregressive Random effect model with the Fast Double Bootstrap approach is able to explain the diversity of poverty rate in the Flores Island by 99.83 percent and fulfilling the assumption of residual normality. The results of the analysis using the FDB approach on the spatial panel show better results than the common spatial panel.

The effect of unit size on the flow and heat transfer performance of the “Schwartz-D” heat exchanger

As a representative type of triple periodic minimal surface (TPMS) topology, the S-D structure exhibits distinctive heat transfer properties and is ideal for constructing high-performance heat exchangers (HXs). To explore the effect of unit size on the flow and heat transfer performance, three crossflow S-D HXs with different unit sizes and the same porosity are designed and produced by metal additive manufacturing in this study. Simulation results show that the reduction in unit size induces a larger scale of bifurcation flow and increases the frequency of flow area change in HX. Experimental results demonstrate that when the smallest unit size is adopted, the HX's effectiveness can be improved by at least 10%, but at the cost of a 42% increase in pressure drop. Meanwhile, the advantage of small unit size in heat transfer enhancement will be further expanded under large flow rate conditions. In addition, it is found that the effect of flow ratio on the heat transfer performance of the S-D HXs appears to be linear, and the unit-based Reynold number may be an appropriate dimensionless parameter for correlating their pressure drop and heat transfer data. All in all, this study is expected to provide a better understanding and guidance for the design and optimization of TPMS HXs.

Epidemiologic assessment of dental health in the military exposed to toxic chemicals

Relevance. Destruction of toxic chemicals is impregnated with hazardous working conditions. In this regard, health monitoring in such workers is subject to more stringent requirements. Occupation-related difficulties in dental care availability cause faster dental health deterioration in the military. This adds relevance to finding and developing modern, rational and effective therapy and prevention measures tailored to specific working conditions the sites of toxic waste destruction.The objective is to evaluate the prevalence and structure of dental diseases and oral cavity disorders in the military exposed to toxic chemicals.Methods. A total of 178 male and female contracted military aged 27-50 years were examined within general medical examination required for admission to work with toxic chemicals. Standard dental methods were used during the examination: interview, visual, physical, and instrumental examinations. Examination data were fed into individual military medical records (form No. 2), as well as into earlier record forms.Results and discussion. Examined patients showed high prevalence of dental diseases (99.4 %), in particular, diseases of dental hard tissues and complicated dental caries. No less than half of the examined (54.5 %) required orthopedic dental treatment. More than 80 % of the examined revealed poor oral hygiene.Conclusion. Considering the high demand (90 %) for sanitation among the military, causing the 25% level of complicated f caries, with average tooth crown destruction score of 0.9 and absence of a staff dentist due to the small size of military units, it is deemed reasonable to involve specialists based on a prior agreed schedule and ensure compliance with developed methods and recommendations.

Building back better: Granular energy technologies in green recovery funding programs

Building back better: Granular energy technologies in green recovery funding programs

Runoff and soil loss in biocrusts and physical crusts from the Tabernas Desert (southeast Spain) according to rainfall intensity.

Biological soil crusts (biocrusts) influence hydrological and erosive processes in drylands, and their effects increase with hypothetic successional development. Runoff and raindrops, both dependent on rain intensity, are among the main causes of erosion in these areas. However, little is known about the existence of soil loss nonlinearity in relation to rain intensity and crust types; this nonlinearity could control biocrust succession and dynamics. The assumption of biocrust types as successional stages, which allow space-for-time sampling, makes it advisable to include all the successional stages when exploring possible nonlinearity. We considered seven types of crusts, three physical and four biological. We created four rainfall intensity levels in controlled laboratory conditions: 18, 60, 120, and 240 mm/h. In all but the last, we conducted the experiments at two levels of antecedent soil moisture. Generalized Lineal Models enabled us to test for differences. These analyses confirmed previous knowledge regarding the significant effect of rainfall intensity, crust type and antecedent soil moisture and their interactions on runoff and soil loss, despite the small sample size of the sample units. For example, runoff, and particularly soil loss, decreased along succession. Moreover, some results were novel: the runoff coefficient increased only up to 120 mm/h of rain intensity. A decoupling between runoff and soil loss occurred at high intensities. Soil loss increased as rainfall intensity increased only up to 60 mm/h, and then it decreased, mainly due to physical crusts, because of the formation of a water sheet on the surface due to the incoming rainwater exceeding the drainage capacity. Although soil loss was greater in the incipient cyanobacteria than in the most developed lichen biocrust (Lepraria community), the protection provided by any biocrust against soil loss was great compared to the physical crust, and almost as strong at all rain intensities. Soil loss increased with antecedent soil moisture only in physical crusts. Biocrusts resisted the rain splash even at a rainfall intensity of 240 mm/h.

IGCT Gate Unit for Zero-Voltage-Switching Resonant DC Transformer Applications

Recently, integrated gate-commutated thyristors (IGCTs) have shown a great potential for the soft-switching dc transformer applications based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter. The zero-voltage switching that is present in this converter topology enables an operation of IGCTs without clamping circuit and with significantly higher switching frequencies, while maintaining the exceptionally low conduction losses. The high voltage and current ratings of the IGCTs make them a preferred choice for an efficient bulk power transmission. This article shows how gate units for IGCTs can be optimized for this soft-switching application. It presents a simplification of the driving topology and the design process for high switching frequencies. This results in low power consumption and a very small size of the gate unit. The prototype of the gate unit is built and experimentally validated in a 2.5 kV 0.75 kA resonant operation of the IGCT.

Magnetic field microscope using high-sensitivity giant magneto-resistance sensor with AC field modulation

A new high-sensitivity giant magneto-resistance (GMR) sensor system was developed and applied to a magnetic field microscope for which a magneto-impedance (MI) sensor was used as a high-sensitivity magnetic probe. The GMR sensor system achieved a detectivity of 13 pT/√Hz at 100 Hz. The sensing limit and spatial resolution were examined compared with the MI sensor. A 100 Hz AC magnetic field from a patterned Cu line was imaged. The GMR sensor showed better spatial resolution than that of the MI sensor owing to its small sensor unit size. The sensing limit was the same for both the GMR sensor and the MI sensor. This limit is due to ambient magnetic field noise. The GMR sensor could reduce this noise by differential detection using two sensor units. These results suggest that the GMR sensor system has advantages for application to the magnetic field microscopes compared with the MI sensor.

Development and validation of rare earth modified Fe-BEA SCR catalyst for mitigation of NOx from NH3 gas turbine

This study investigated NH3-SCR of NOx from the exhaust of 300 kW NH3 gas turbine using Fe-zeolite and rare earth modified Fe-zeolite catalyst. As part of greenhouse gas reduction program, a gas turbine for power generation using NH3 and/or natural gas as fuel is developed where the challenge was to develop a catalyst that reduces NOx with high efficiency with minimum NH3 consumption as well as small SCR unit size. From laboratory bench scale evaluations Fe-BEA catalyst was identified to show desired NOx conversion, however upon aging in presence of steam at 800 °C the performance degraded. The Gd modified Fe-BEA catalyst showed high NOx reduction >98% at 600 °C and remained durable even after aging at 800 °C. The characterization results of XRD, UV and NH3-TPD revealed that addition of rare earth cations to Fe-BEA decreased the agglomeration of active iron species and stabilized the zeolite structure leading to minimal decrease in NH3 storage sites all of which are responsible for increased NOx conversion. The Gd/Fe-BEA catalyst was scaled up and tested behind a 300 kW NH3 gas turbine and it was demonstrated that the reduction of NOx from 477 ppm to 4.3 ppm, which is below the set target of 70 ppm in the exhaust was achieved.

A Bioinspired Ultratough Composite Produced by Integration of Inorganic Ionic Oligomers within Polymer Networks.

The nacre-inspired laminates are promising materials for their excellent mechanics. However, the interfacial defects between organic-inorganic phases commonly lead to the crack propagation and fracture failure of these materials under stress. A natural biomineral, bone, has much higher bending toughness than the nacre. The small size of inorganic building units in bone improves the organic-inorganic interaction, which optimizes the material toughness. Inspired by these biological structures, here, an ultratough nanocomposite laminate is prepared by the integration of ultrasmall calcium phosphate oligomers (CPO, 1 nm in diameter) within poly(vinyl alcohol) (PVA) and sodium alginate (Alg) networks through a simple three-step strategy. Owing to the small size of inorganic building units, strong multiple molecular interactions within integrated organic-inorganic hierarchical structure are built. The resulting laminates exhibit ultrahigh bending strain (>50% without fracture) and toughness (21.5-31.0 MJ m-3), which surpass natural nacre and almost all of the synthetic laminate materials that have been reported so far. Moreover, the mechanics of this laminate is tunable by changing the water content within the bulk structure. This work provides a way for the development of organic-inorganic nanocomposites with ultrahigh bending toughness by using inorganic ionic oligomers, which can be useful in the fields of tough protective materials and energy absorbing materials.

Can IMU Provide an Accurate Vertical Jump Height Estimate?

The aim of the present study was to determine if an inertial measurement unit placed on the metatarsal part of the foot can provide valid and reliable data for an accurate estimate of vertical jump height. Thirteen female volleyball players participated in the study. All players were members of the Republic of Serbia national team. Measurement of the vertical jump height was performed for the two exemplary jumping tasks, squat jump and counter-movement jump. Vertical jump height estimation was performed using the flight time method for both devices. The presented results support a high level of concurrent validity of an inertial measurement unit in relation to a force plate for estimating vertical jump height (CMJ t = 0.897, p = 379; ICC = 0.975; SQJ t = −0.564, p = 0.578; ICC = 0.921) as well as a high level of reliability (ICC &gt; 0.872) for inertial measurement unit results. The proposed inertial measurement unit positioning may provide an accurate vertical jump height estimate for in-field measurement of jump height as an alternative to other devices. The principal advantages include the small size of the sensor unit and possible simultaneous monitoring of multiple athletes.

Green inclusive leadership and green creativity in the tourism and hospitality sector: serial mediation of green psychological climate and work engagement

Green creativity contributes to green innovation and green sustainability in both the manufacturing and services sectors. However, academic research offering more nuanced insights about the drivers of green creativity (GCRT) is deficient, particularly within the tourism and hospitality sector. The present study thus theorized a model based on the Componential Theory of Creativity (CTC) to examine green inclusive leadership (GIL), green psychological climate (GPC), and green work engagement (GWE) as antecedents of GCRT. The model not only posits the direct associations but also accommodates a more complex interaction of variables by anticipating the mediation effect of GPC and GWE on the association of GIL and GCRT. The data collected through Prolific from 302 employees in the tourism and hospitality sector is analyzed using PROCESS macro. Findings confirmed a positive association of GIL with GPC and GCRT, GPC with GWE, and GWE with GCRT. In addition, the sequential mediation effect of GPC and GWE is supported. These results are useful for the tourism and hospitality sector, where a relational leadership style, such as inclusive leadership, is more relevant for fostering creativity, given the small size of business units, the sector's service-oriented nature, and the power of employees at the point of interface with the customers.

Improving Language Translation Using the Hidden Markov Model

Translation software has become an important tool for communication between different languages. People’s requirements for translation are higher and higher, mainly reflected in people’s desire for barrier free cultural exchange. With a large corpus, the performance of statistical machine translation based on words and phrases is limited due to the small size of modeling units. Previous statistical methods rely primarily on the size of corpus and number of its statistical results to avoid ambiguity in translation, ignoring context. To support the ongoing improvement of translation methods built upon deep learning, we propose a translation algorithm based on the Hidden Markov Model to improve the use of context in the process of translation. During translation, our Hidden Markov Model prediction chain selects a number of phrases with the highest result probability to form a sentence. The collection of all of the generated sentences forms a topic sequence. Using probabilities and article sequences determined from the training set, our method again applies the Hidden Markov Model to form the final translation to improve the context relevance in the process of translation. This algorithm improves the accuracy of translation, avoids the combination of invalid words, and enhances the readability and meaning of the resulting translation.

A miniaturized frequency selective rasorber with high selectivity passband and wideband absorption properties

A miniaturized frequency selective rasorber (FSR) with high selectivity passband and wideband absorption properties is presented. Its performance as an absorber over a wide absorption band from 8.08 to 18.08 GHz through the structure of metal incurved square loop structure loaded resistors. The frequency selective surface (FSS) using Jerusalem cross array and metallic patch realizes the transmission frequency band from 2.7 to 3.52 GHz. And the insertion loss (IL) is 0.37 dB at 3.08 GHz. The symmetry and miniaturized elements design enable the proposed FSR to achieve satisfactory incident angle stability. Its small unit size effectively avoids the generation of grating lobes in the absorption band and the interference to Radar Cross Section (RCS) reduction.

Optimal placement and sizing of distributed generation with small signal stability constraint

In recent decades, galloping growth of distributed generation (DG), and its vital role from technical, financial, and environmental point of view, has made it more prominent that DG and its utilization need to be analyzed meticulously. Since most DG units’ output power is DC or is not in accordance with network frequency, they need to be connected to the network via power electronic interface. Therefore, the behavior of power electronic interface and their low inertia can affect distribution system’s small signal stability and optimal size and location of DG unit consequently. In this paper, dynamic models for Inverter-Based DG unit (IBDG), network branches, and loads are utilized in order to scrutinize impacts of small signal stability constraint on optimal size and location of IBDG in radial distribution system (RDS). Similar to many previous studies, a genetic algorithm has been implemented to find optimal size and location of IBDG with the aim of total active power loss minimization. Simulation results on the IEEE 33-bus test system show that, DG placement studies without small signal stability consideration, can lead to inaccurate outcomes which have deleterious impacts on small signal stability.

Combined effects of tool surface texturing, cutting parameters and minimum quantity lubrication (MQL) pressure on micro-grinding of BK7 glass

Capability of sintered micro-grinding tool is limited by low chip space, ineffective lubrication access and premature loading which results in high cutting forces and brittle mode fractures on the work surfaces. Usage of textured tool is one of the methods to avoid aforesaid phenomena and to achieve high cutting performance. On machine fabrication of textured micro-tools and correlating their cutting mechanism with texture dimension are some of the primary challenges. A new electric discharge texturing method for on-machine fabrication of textured tools is devised and the tools with optimum intermittent ratio but varying texture dimensions are fabricated. Micro-grinding experiments are carried out on BK7 glass to establish the correlation between cutting performance with texture dimension, cutting parameters and MQL (minimum quantity lubrication) pressure. It is concluded that tool with small size and large number of texture units reduced the cutting forces, surface roughness and edge chipping by 25–35 % of those obtained by a tool without texture at depth of cut 10 μm and feed rate 5 mm/min. The amount of reductions of these two process parameters even reached to 50–60 % at high depth of cut 40 μm and feed rate 11 mm/min. The reduction in output parameters is supported by the observation of effective migration of chips in the passive areas. It is also established in this study that MQL spray droplet size should be very close to the texture dimension to ensure maximum cutting fluid access in the machining zone. Analytical derivation of penetration depth for textured tools indicated delayed chances of ductile to brittle transition when the tools with small size texture units are used in place of the tools with large size texture units.

On the Design of Ultrawideband Circuit Analog Absorber Based on Quasi-Single-Layer FSS

In this letter, an ultrawideband and single-layer circuit analog absorber with a low profile and small unit size is proposed. The absorber is composed of a Rogers 4003 dielectric with two square loop arrays, respectively, printed on the top and bottom, and a metal ground below. Lumped resistors are embedded on the four edges of the square-loop arrays to introduce resistance loss. Equivalent circuit, input impedance, and current distribution are then presented to provide great insight into the existence of three resonances and wideband. The absorber offers a fractional absorption bandwidth of 132.3% (4.91:1) with at least 10 dB reflection reduction. The thickness and the unit size are, respectively, reduced to $0.075\lambda _{L}$ (wavelength at the lowest frequency) and $0.13\lambda _{L}$ , leading to a good performance under oblique incidence. A good agreement between the calculated, simulated, and measured results validates the proposed design.

Low risk pregnancies after a cesarean section: Determinants of trial of labor and its failure.

IntroductionIn pregnancies after a previous cesarean section (CS), a planned repeat CS delivery has been associated with excess risk of adverse outcome. However, also the alternative, a trial of labor after CS (TOLAC), has been associated with excess risks. A TOLAC failure, involving a non-planned CS, carries the highest risk of adverse outcome and a vaginal delivery the lowest. Thus, the decision regarding delivery mode is pivotal in clinical handling of these pregnancies. However, even with a high TOLAC rate, as seen in Norway, repeat CSs are regularly performed for no apparent medical reason. The objective of the present study was to assess to which extent demographic, socioeconomic, and health system factors are determinants of TOLAC and TOLAC failure in low risk pregnancies, and whether any effects observed changed with time.Materials and methodsThe study group comprised 24 645 second deliveries (1989–2014) after a first delivery CS. Thus, none of the women had prior vaginal deliveries or more than one CS. Included pregnancies were low risk, cephalic, single, and had gestational age ≥ 37 weeks. Data were obtained from the Medical Birth Registry of Norway (MBRN). The exposure variables were (second delivery) maternal age, length of maternal education, maternal country of origin, size of the delivery unit, health region (South-East, West, Mid, North), and maternal county of residence. The outcomes were TOLAC and TOLAC failure, as rates (%), relative risk (RR) and relative risk adjusted (ARR). Changes in determinant effects over time were assessed by comparing rates in two periods, 1989–2002 vs 2003–2014, and including these periods in an interaction model.ResultsThe TOLAC rate was 74.9%, with a TOLAC failure rate of 16.2%, resulting in a vaginal birth rate of 62.8%. Low TOLAC rates were observed at high maternal age and in women from East Asia or Latin America. High TOLAC failure rates were observed at high maternal age, in women with less than 11 years of education, and in women of non-western origin. The effects of health system factors, i.e. delivery unit size and administrative region were considerable, on both TOLAC and TOLAC failure. The effects of several determinants changed significantly (P < 0.05) from 1989–2002 to 2003–2014: The association between non-TOLAC and maternal age > 39 years became weaker, the association between short education and TOLAC failure became stronger, and the association between TOLAC failure and small size of delivery unit became stronger.ConclusionLow maternal age, high education, and western country of origin were associated with high TOLAC rates, and low TOLAC failure rates. Maternity unit characteristics (size and region) contributed with effects on the same level as individual determinants studied. Temporal changes were observed in determinant effects.

A 32-Unit 240-GHz Heterodyne Receiver Array in 65-nm CMOS With Array-Wide Phase Locking

This paper reports a 32-unit phase-locked dense heterodyne receiver array at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> = 240 GHz. To synthesize a large receiving aperture without large sidelobe response, this chip has the following two features. The first feature is the small size of the heterodyne receiver unit, which is only λ(f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> )/4 × λ(f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> )/2. It allows for the integration of two interleaved 4 × 4 arrays within a 1.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> die area for concurrent steering of two independent beams. Such unit compactness is enabled by the multi-functionality of the receiver structure, which simultaneously accomplishes local oscillator (LO) generation, inter-unit LO synchronization, input wave coupling, and frequency downconversion. The second feature is the high scalability of the array, which is based on a strongly coupled 2-D LO network. Large array size is realizable simply by tiling more receiver units. With the upscaling of the array, our de-centralized design, contrary to its prior centralized counterparts, offers invariant conversion loss and lower LO phase noise. Meanwhile, the entire LO network is also locked to a 75-MHz reference, facilitating phase-coherent pairing with external sub-terahertz transmitters. A chip prototype using a bulk 65-nm CMOS technology is implemented, with a dc power of 980 mW. Phase locking of the 240-GHz LO is achieved among all 32 units, with a measured phase noise of -84 dBc/Hz (1-MHz offset). The measured sensitivity (BW = 1 kHz) of a single unit is 58 fW. Compared to previous square-law detector arrays of comparable scale and density, this chip provides phase-sensitive detection with ~4300× sensitivity improvement.

Urban development-induced displacement and quality of life in Kolkata

This paper draws together issues of urban development-induced displacement and resettlement and the quality of life of the affected population over the longer term. It reviews settlement strategies related to the Kolkata Environmental Improvement Project, exploring residents’ recollection of the relocation process and comparing and contrasting the situation over time of two groups of low-income households: those who refused a resettlement package and chose to continue to reside in their canalside huts; and those who accepted the package and moved into new flats provided by the government. The paper highlights issues of livelihoods, social cohesion and sanitation among both sets of households to find out whether those who were resettled experienced improvement in these aspects of their lives. Findings point to resettled households’ overall satisfaction with sanitation despite periodic lapses in functioning, and a modicum of social support, but significant livelihood problems among the poorest households, and dissatisfaction with the small size of units.