External Efficiency Research Articles

Monte Carlo Modeling of a High‐Efficiency Tandem Luminescent Solar Concentrator Containing a Polarization Volume Grating Layer

This article develops a Monte Carlo model to optimize a newly introduced tandem luminescent solar concentrator. This innovative structure comprises two parallel transparent polymeric waveguides separated by an air gap. The first waveguide, which is exposed to sunlight, contains fluorophores and performs as a traditional luminescent solar concentrator. In contrast, the second waveguide is equipped with an inner polarization volume grating layer, strategically placed to couple the emitted photons within the escape cone, directing them into the second waveguide and preventing reabsorption. The finite difference time domain method is employed to optimize the performance of this grating. The results show a significant improvement in external photon efficiency compared to the conventional luminescent solar concentrator.

Conversion of 30 W laser light at 1064 nm to 20 W at 2128 nm and comparison of relative power noise

Abstract All current gravitational wave (GW) observatories operate with Nd:YAG lasers with a wavelength of 1064 nm. The sensitivity of future GW observatories could benefit significantly from changing the laser wavelength to approximately 2 μm combined with exchanging the current room temperature test mass mirrors with cryogenically cooled crystalline silicon test masses with mirror coatings from amorphous silicon and amorphous silicon nitride layers. Laser light of the order of ten watts with a low relative power noise would be required. Here we use a laboratory-built degenerate optical parametric oscillator (OPO) to convert the light from a high-power Nd:YAG laser to 2128 nm. With an input power of 30 W, we achieve an output power of 20 W, which corresponds to an external conversion efficiency of approximately 67%. We find that the relative power noise spectrum marginally increases during the wavelength conversion process. Our result is an important step in the development of low-noise light around 2 μm based on existing low-noise Nd:YAG lasers.

Effect of trimetazidine dihydrochloride therapy on myocardial external efficiency in preclinical individuals with an HCM sarcomeric gene mutation

Abstract Background Hypertrophic cardiomyopathy (HCM) is frequently caused by pathogenic gene variants, i.e. mutations in genes encoding sarcomere proteins. Previous studies have shown that preclinical asymptomatic individuals with a heterozygous sarcomere mutation have decreased myocardial external efficiency (MEE), which is thought to be a key pathomechanism in the onset and progression of HCM. Purpose In the ENERGY trial, preclinical individuals with an HCM sarcomere gene mutation without hypertrophy were treated with the metabolic anti-anginal drug trimetazidine (TMZ) to determine whether the reduced MEE can be corrected at an early pre-hypertrophic disease stage. Methods 40 MYBPC3 and MYH7 asymptomatic mutation carriers without hypertrophy were treated for eight weeks with TMZ or placebo in a double-blind randomized study design. Directly before and after treatment, study participants underwent an [11C]-acetate PET/CT-scan and cardiac magnetic resonance imaging to measure MEE. A cardio-pulmonary exercise test was performed to measure the influence of TMZ on exercise parameters. Results Eight weeks of treatment with TMZ 20mg three times daily did not significantly alter MEE compared to placebo. The mean MEE changed from 30.3±3.8 percent to 29.8±4.3 percent in the placebo group and from 30.1±4 percent to 29.1±4 percent in the TMZ group. After adjustment for baseline, the TMZ group did not have a significantly different MEE (95% CI, -2.863 to 1.986, P=0.68) compared to placebo. Exercise parameters VO2max and respiratory exchange ratio were not significantly altered by treatment with TMZ. Conclusion The ENERGY trial is the first proof-of-concept randomized controlled trial with well-matched (age, sex, mutation) groups to test the hypothesis that TMZ improves MEE at a preclinical disease stage. We conclude that metabolic therapy does not correct reduced MEE in an early disease stage of HCM.methodsprimary outcome

The hearts of large mammals generate higher pressures, are less efficient and use more energy than those of small mammals.

A prevailing assumption in the cardiovascular field is that the metabolic rate of the heart is a constant proportion of a mammal's whole-body aerobic metabolic rate. In this Commentary, we assemble previously published cardiovascular, metabolic and body mass data from matched terrestrial mammalian species, at rest and during heavy exercise, and reveal scaling relationships that challenge this assumption. Our analyses indicate that the fractional metabolic cost of systemic perfusion compared with whole-body metabolic rate increases significantly with body size among resting mammals, from ∼2.5% in a mouse to ∼10% in an elephant. We propose that two significant body size-dependent effects contribute to this conclusion; namely, that larger species generate higher mean systemic arterial blood pressure and that their myocardium operates with lower external mechanical efficiencies compared with those of smaller species. We discuss potential physiological and mechanical explanations, including the additional energy needed to support the arterial blood column above the heart in larger species, especially those with long necks, as well as the possible sources of greater internal energy losses from the heart of larger species. Thus, we present an updated view of how increasing blood pressure and decreasing efficiency of the myocardium result in an increasing fractional metabolic cost of perfusion as body size increases among resting mammals.

The Assessment of External Nasal Valve Efficiency After Le Fort I Surgery: Erratum.

The Assessment of External Nasal Valve Efficiency After Le Fort I Surgery: Erratum.

Optimizing the order picking and delivery process to the final recipient

The aim of this study is to analyse and evaluate the order picking process and the transport of products to customers, taking into account the specific characteristics and potential of small and medium-sized industrial enterprises. Scientific standards and selected indicators for measuring the efficiency and quality of transport and order picking processes were used to achieve the intended objectives. The research was conducted in a small, family-owned manufacturing and trading company specialising in the production and sale of wrought iron finishing elements and fences. The analysis covered both internal and external transport processes. It was shown that the order picking process in the studied company is largely based on manual procedures, which, despite high precision, generates time-consuming activities related to the movement of warehouse employees. External transport efficiency indicators showed high efficiency and appropriate use of transport resources. The high quality of deliveries, as measured by on-time and reliability indicators, confirms customer satisfaction. The study was conducted in one company, which is a limitation. Future studies should include more companies from the same sector. Proposed improvements need to be verified sometime after implementation and solutions resulting from data analysis can help SMEs in similar industries to improve their logistics processes. The work brings a new approach to the analysis of order picking and transport processes in the context of SMEs, providing practical solutions and indicating areas for further research. It is aimed at logistics managers, researchers and practitioners interested in optimising logistics processes in the industrial sector.

The Impact of 3D Printing Technology on the Improvement of External Wall Thermal Efficiency—An Experimental Study

Three-dimensional printing technology continues to evolve, enabling new applications in manufacturing. Extensive research in the field of biomimetics underscores the significant impact of the internal geometry of building envelopes on their thermal performance. Although 3D printing holds great promise for improving thermal efficiency in construction, its full potential has yet to be realized, and the thermal performance of printed building components remains unexplored. The aim of this paper is to experimentally examine the thermal insulation characteristics of prototype cellular materials created using 3D additive manufacturing technologies (SLS and DLP). This study concentrates on exploring advanced thermal insulation solutions that could enhance the energy efficiency of buildings, cooling systems, appliances, or equipment. To this end, virtual models of sandwich composites with an open-cell foam core modeled after a Kelvin cell were created. They were characterized by a constant porosity of 0.95 and a pore diameter of the inner core of the composites of 6 mm. The independent variables included the different material from which the composites were made, the non-uniform number of layers in the composite (one, two, three, and five layers) and the total thickness of the composite (20, 40, 60, 80, and 100 mm). The impact of three independent parameters defining the prototype composite on its thermal insulation properties was assessed, including the heat flux (q) and the heat transfer coefficient (U). According to the experimental tests, a five-layer composite with a thickness of 100 mm made of soybean oil-based resin obtained the lowest coefficient with a value of U = 0.147 W/m2·K.

Aggregation-Induced Enhanced Red Emission Graphene Quantum Dots for Integrated Fabrication of Luminescent Solar Concentrators.

Graphene quantum dots (GQDs) commonly suffer from the fluorescence problem of aggregation-caused quenching under high-concentration loading or in the solid state, which seriously hinders the application. Here we report a type of GQDs with red aggregation-induced enhanced emission (AIEE). It is confirmed that the aggregation state of the AIEE GQDs is a J-aggregate. The GQDs/poly(methyl methacrylate) film presented a photoluminescence quantum yield as high as 60.81%, and the record-high performance of luminescent solar concentrators (LSCs) was achieved. The power conversion efficiency (ηPCE) is up to 8.35% and the external optical efficiency (ηext) is ∼8.99% for the GQD-based LSCs (45 mW/cm2). Even under one sun illumination (100 mW/cm2), the corresponding ηPCE and ηext values are 3.12% and 4.52%, respectively. The internal photon efficiency (ηint) of an LSC device is about 5.02%. The synthesis of AIEE GQDs bridges the research gap in the emission mechanism of AIEE in GQDs.

Utilizing molecular states of carbon quantum dots (CQDs) to efficiently harvest outdoor and indoor energy via luminescent solar concentrator

Luminescent solar concentrators (LSCs) offer a huge potential for electricity generation due to their ability to harvest direct and diffused light. Among numerous fluorophores for LSCs, carbon quantum dots (C-QDs) are promising candidates due to their non-toxic nature, tunable optical features, and cost-effective synthesis. State-of-the-art LSCs utilizing C-QDs focus on solar energy harvesting, while their potential to harness indoor light for electricity generation is yet to be explored. In this study, we rationally fabricated C-QDs based LSC for efficient energy harvesting under both outdoor and indoor illuminations. Through a facile solvothermal pyrolysis technique, we synthesized the molecular states assisted C-QDs exhibiting a strong absorbance in the visible region that matched well with the outdoor and indoor light spectra. Laminated LSCs were fabricated by coating C-QDs/polyvinyl alcohol (PVA) film (photoluminescence quantum yield 71 %) on two glass substrates and joining them with an interlayer of refractive index matching polymer. Given geometry not only protects C-QDs/PVA film from external damage but also prevents light scattering losses that were prominent in an open C-QDs/PVA layer. External efficiency (ηext) of the small-to-large area LSCs under different illuminations were estimated using an analytical approach. The results showed that under outdoor (air mass 1.5 global spectrum) illumination and without scattering background, a large-area (10 × 10 × 0.6 cm3) LSC at an optimized concentration of C-QDs exhibited ηext of 3.1 %. When connected with the silicon PV cell, the same LSC yielded a power conversion efficiency (ηPCE) of 0.34 %. Among various indoor illuminations (light-emitting diode (LED)-daylight, LED-warm white, and fluorescent-daylight (CFL)), the best performance was shown under LED-daylight with the ηext and ηPCE of 7.4 % and 0.30 %, respectively. This study offers enormous potential for the adoption of C-QDs based LSC not only in building exteriors (such as windows and facades) but also in the places where artificial lights are used.

(Invited) Silicon Nanocrystals and Electrum Nanoclusters with High Quantum Yield for Light Converting Applications

While QDs are typically made of semiconductors, metals at low dimensions also turn to discrete electronic structure. The characteristic transition size from bulk to nanodot is lower, because Fermi level position is at the band middle, while discretization of levels starts from the band edge. Therefore, only for sizes of a metal entity ~ 1 nm a QD-like behavior manifests.Here we show that metal nanoclusters Au16Ag7 of an electrum alloy (gold-silver) with adamantanethiolate ligands possess PL quantum yield of ~ 70% in a thiol-ene polymer matrix [1]. PL is in NIR range with a large Stokes shift. Due to parity-forbidden transition the PL lifetime is in microseconds. These characteristics are similar to silicon QDs, where optical transition is also partly forbidden. Luminescence from Si QDs (5-10 nm size) may also feature high quantum efficiency when a defect-free core with good surface passivation is prepared. We have demonstrated a new synthesis method, which can reduce precursor cost by an order of magnitude from the established HSQ-based technique [2]. Si QDs prepared in this way have near-unity internal and > 50% external (quantum yield) efficiency with a large Stokes shift. In both nanomaterials the re-absorption is suppressed, which is of value for several applications.One such application is a semi-transparent photovoltaics for glazing in building-integration. It is based on a luminescent solar concentrator concept, where high efficiency and a large Stokes shift are necessary requirements for nanophosphors. In this configuration absorbed solar light is re-emitted and a large fraction of it is guided by total internal reflection to the edges for collection by standard solar cells. As a proof-of-concept we fabricated 20x20 cm2 prototypes, where Si QD-doped polymer layer is sandwiched between glass plates in a triplex geometry. Such “solar windows” feature high transparency (>80%), low haze (<3%), high color rendering index (~ 88) and, at the same time, deliver up to 0.6 W of electrical peak power under one sun [3]. Original measurement techniques were developed to characterize large-area devices [4,5].

Mapping Losses through Empirical Extraction of the Spatial External Luminescence Efficiency

Mapping Losses through Empirical Extraction of the Spatial External Luminescence Efficiency

Low-noise short-wavelength pumped frequency downconversion for quantum frequency converters

We present a highly efficient low-noise quantum frequency converter from the visible range to telecom wavelengths, combining a pump laser at intermediate frequency resonantly enhanced in an actively stabilized cavity with a monocrystalline bulk crystal. A demonstrator for photons emitted by nitrogen-vacancy-center qubits achieves 43% external efficiency with a noise photon rate per wavelength (frequency) band of 2 s−1/pm(17 s−1/GHz) – reducing the noise by two orders of magnitude compared with current devices based on periodically poled crystals with waveguides. With its tunable output wavelength, this device enables the generation of indistinguishable telecom photons from different network nodes and is, as such, a crucial component for a future quantum internet based on optical fiber.

How Digital Transformation Enables Corporate Sustainability: Based on the Internal and External Efficiency Improvement Perspective

The promotion of the simultaneous advancement of digitalization and sustainability has emerged as a crucial concern for achieving high-quality economic growth within the framework of the ‘dual-carbon’ objective. Based on the micro data of Chinese A-share listed companies between 2009 and 2022, this paper systematically examines how digital transformation affects the ESG performance of enterprises in order to explore the effective path for digitalization to promote the sustainable development of enterprises. The results indicate that implementing digital transformation can enhance the ESG performance of enterprises, which in turn boosts their capacity for sustainable development. The test of the mechanism indicates that enhancing internal total factor productivity and optimizing external financial allocation efficiency are the key strategies for driving ESG performance improvement in companies through digital transformation. Further analysis reveals that the improvement effect of digital transformation on corporate ESG performance is more prominent in state-owned enterprises, non-heavily polluted industries, central and western, and low-marketization regions. In addition, while digital transformation enhances the ESG performance of enterprises themselves, it also creates beneficial ripple effects on the ESG metrics of their suppliers and customers, ultimately boosting the sustainable growth of the entire supply chain. The conclusions of this paper help to deepen the potential value of digital transformation and provide policy and practical insights for achieving sustainable economic development.

High-efficiency laminated luminescent solar concentrators based on carbon dots and nanorings

Creation of novel fluorescent nanomaterials with high photoluminescence quantum yield (PLQY) will lead to high-efficiency luminescent solar concentrators (LSCs). Herein, two kinds of carbon dots (CDs), e.g., blue and green emissive CDs and one novel carbon nanorings (NRs) with yellow emission are synthesized by the solvothermal method. Diaminobenzenesulfonic acid is used as one main precursor to create blue, green emission carbon dots (B/GCDs) and yellow emission carbon nanorings (YCNRs). Importantly, the PLQYs of B/GCDs and YCNRs are 59.8±3.2 %, 12.2±0.7 % and 63.2±1.5 %, respectively. Moreover, B/GCDs and YCNRs are used as fluorescent nanomaterials to construct laminated LSCs with single-layer and double-layer through one-step photopolymerization technique. For single-layer laminated LSCs, YCNRs-based LSCs have the maximum external optical efficiency (ηopt), up to 3.05 %. Furthermore, for double-layer laminated LSCs, the LSCs based on BCDs and YCNRs achieve the highest ηopt of 4.09 %. Compared to single-layer laminated LSCs, the double-layer laminated LSCs show an increase of 34 % in ηopt. Their internal quantum efficiency (ηint) of 29.88 % and external quantum efficiency (ηext) of 25.18 % are obtained, respectively. The presented values are just for single-wavelength excitation. Thus, the synthesis of novel YCNRs with high PLQYs contributes to the optical performances at a large level. Remarkably, the optimal double-layer laminated LSCs show good transparency.

High thermal stability and high-performance efficiency capability of light sources–based rate equation models in optical fiber transmission systems

Abstract This paper clarified the high thermal stability and high-performance efficiency capability of silicon light sources–based rate equation models in the optical fiber transmission systems. The laser diode and light emitting diode output power variations are measured with input injection current under various ambient temperature effects. The light source differential quantum efficiency is demonstrated for both LED and laser diode with different injection input current and various temperature variations. The LED/laser diode light source external efficiency is clarified with different injection input current and various temperature variations. The LED/laser diode light source total efficiency is measured with different injection input current and various temperature variations. As well as the laser diode and light emitting diode, threshold current variations are demonstrated clearly with input injection current under room temperature and various spectral thermal effects. The laser diode and light emitting diode power dissipation variations are measured with input injection current under room temperature and various spectral thermal effects.

Design cost minimization of a reinforced concrete column section using overnew swarm-based optimization algorithms

It is very tiresome for a practiser to detect the best feasible sizing design of structural members including reinforced concrete columns that is a highly nonlinear and complicated structural engineering optimization problem. This is due to such a design is practically conducted via conventional trial-and-error computing methods in which resistance to external loads, cost efficiency, and aesthetic factors, etc. have to be considered. This study focuses on minimizing the design cost of primarily proposed reinforced concrete column design problem via three overnew swarm-based optimizers such as Coati Optimization Algorithm, Fox Optimizer and Pelican Optimization Algorithm (POA) that are firstly utilized for this purpose. In this regard, the type of steel rebar distribution, the characteristic strength of the concrete, the height and width of the column section, and the number and diameter of the rebars are treated as discrete design variables of the newly proposed complex reinforced concrete column design cost optimization problem. In solution, the design requirements specified in practice code provisions should also be met. Here, Turkish Building Earthquake Code 2018 specifications are considered as practice structural design constraints. Consequently, the algorithmic performances of three overnew swarm-based metaheuristic optimization algorithms are compared and evaluated in detail. Amongst them, the POA shows most fruitful algorithmic design solution performance.

Development and synthesis of anthracene-based fluorescence material for non-doped OLEDs

Efficient organic blue materials are essential to develop highly efficient organic light-emitting diodes. However, there is a challenge to commercialize efficient blue compounds due to the fundamentally wide band gap and the lack of pure blue emitters. In this study, the new anthracene-based fluorescent emitter, (4-(10-(4-(9H-carbazol-9-yl)-2-methylphenyl)anthracen-9-yl)-3-methylphenyl)diphenylphosphine oxide (CZm-AN-mPO) was designed and synthesized. The thermal, photophysical and electrochemical properties of the CZm-AN-mPO were systematically investigated. The CZm-AN-mPO exhibits a deep-blue emission at 425 nm and AIE property with a relatively narrow full-width at half maximum of 34 nm. The CZm-AN-mPO based non-doped devices show pure blue emission. The optimized OLEDs indicated maximum external efficiencies of 4.3% and 4.2% at emission layer thickness of 20 nm and 40 nm, respectively.

Leadership and Organizational Performance of Telecommunication Company: an Exploratory Study of Hormuud Telecom in Somalia

This study explores the relationship between leadership styles and organisational performance within the context of Hormuud Telecom, a telecommunications business in Somalia. Given the unique socio-economic, political and security instability context in the country, the study examines the influence of leadership styles, methods, and practices on the organization's overall success. This leadership style appears to correlate positively with key performance metrics such as employee satisfaction, internal and external efficiency, and customer retention. This research seeks to provide significant insights into the dynamics of leadership in the telecoms sector by performing an in-depth investigation of Hormuud Telecom's leadership structure and its impact on several areas of organisational efficiency. Employing a qualitative study technique, the research adopted a qualitative research design incorporating secondary data and observational methodologies to gather insights and comprehend the influence of leadership styles on team leadership styles, employee satisfaction, and operational efficiency. It further examines the prominent leadership behaviours seen at Hormuud Telecom and establishes a relationship between these practices and qualitative improvements in organisational performance. The findings indicate a strong correlation between transformative leadership increased employee engagement and improved performance indicators. Similarly emphasises the significance of adaptive leadership in the swiftly evolving telecom industry like in Somalia, indicating that effective leadership plays a crucial role in enhancing organisational performance under demanding economic and operational conditions. This research enhances the overall discussion on leadership in developing economies and provides practical knowledge for firms functioning in comparable situations.

Enhancing External Combustion Efficiency in Stirling Engine Combustors: Influence of Oxygen Atmosphere, Ejection Ratio, and Pressure

Enhancing External Combustion Efficiency in Stirling Engine Combustors: Influence of Oxygen Atmosphere, Ejection Ratio, and Pressure

Effectiveness of internal auditing from the lens of internal audit factors: empirical findings from the banking sector of Bangladesh

Purpose This study aims to assess the impact of determinants on the effectiveness of internal audit (IA) within the banking industry of Bangladesh. Design/methodology/approach The data was obtained through 152 survey questionnaires from a total of 43 privately owned and six state-owned commercial banks in Bangladesh. The analysis was conducted using structural equation modeling. Findings The findings demonstrate that the independence of internal auditors and the quality of IA substantially impact enhancing the efficiency of IA. On the other hand, the competence of internal auditors and management support in IA functions do not significantly impact the effectiveness of IA. Practical implications The study’s findings may have significant policy implications for the government, regulators, internal auditors, management committees and other stakeholders in establishing programmes to enhance the efficacy of IA as a component of banking audit management reforms. Originality/value This study makes three distinct contributions to the existing literature. Firstly, previous literature focused on the determinants affecting the external audit efficiency of the public companies and banking sectors in Bangladesh (Hasan, 2018; M. M. U. Reza, 2021). In this study, the author enhances the research by presenting empirical findings on the IA effectiveness of banks. Secondly, the author expands the research by incorporating both private and state-owned commercial banks as samples. Thirdly, the study is unique given that it investigates the effectiveness of IA in response to the recent financial scandals in the banking industry of Bangladesh (The Daily Star, 2023).