Acceptance Angle Research Articles

Optical performance investigation for spatially separated non-imaging concentrator with congruent plane concentrating surface

The thermal deformation on the concentrating surface of traditional CPC (Compound Parabolic Concentrator, CPC) is effectively addressed by SCSA-CPC (Separation of Concentrating Surface and Absorber CPC, SCSA-CPC). However, the energy flux density distribution on the absorber of SCSA-CPC is uneven and the concentrating surface is still a curved paraboloid structure, which hinders practical engineering applications and lacks significant economic benefits. In the present research, five kinds of SS-CPCs (Spatially Separated CPC, SS-CPC) with different numbers of congruent plane concentrating surfaces, namely SS-CPC2, SS-CPC3, SS-CPC4, SS-CPC5 and SS-CPC6 were constructed based on non-imaging optics principles. The optical performances of the SS-CPCs were investigated and compared to SCSA-CPC with the same specification. It is found that SS-CPC allows for an increased acceptance angle of up to 41° while effectively improving the uniformity of energy flux density distribution on the absorber. The results also showed that the annual beam radiation collection time can be extended by 43.11 % and SS-CPC has a particular advantage in collecting diffuse radiation, indicating its high adaptability to weather changes. Moreover, due to the congruent planar structure of the concentrating surface, SS-CPC holds promising prospects for practical engineering applications.

An ultra-thin optical polarizer based on weyl semimetals

Recently, Weyl semimetals have been extensively studied due to their unique optical responses, especially in the mid-infrared region. However, the possibility of developing optical polarizers based on Weyl semimetals remains unexplored. In this paper, under the Voigt geometry, we numerically show that an ultra-thin Weyl semimetal film with thickness L = 100 nm can achieve an impressive polarization extinction ratio (more than 40 dB) with a wide acceptance angle. Further, the proposed sandwich structure can effectively adjust the position of the TE mode transmission peak alone, thus obtaining lower insertion loss (from 0.06 dB to 0.03 dB) and wider acceptance range of angle (from 49.5∘ to 71∘). The proposed gradient Fermi level structure eliminates the Fabry-Perot cavity resonance, thus resulting a wider bandwidth (approximately 60 % improvement). Our proposed ultra-thin and wide-angle polarizer may have potential applications in optical communication and omnidirectional polarization detectors.

Broadband long-wavelength upconversion in ultra-short nonlinear crystals.

Since the inception of the second-order nonlinear frequency conversion in 1961, enhancing the inherent low conversion efficiency has been a primary objective. This goal has been successfully accomplished through the utilization of cm-long nonlinear crystals characterized by high quality and nonlinearity, coupled with versatile phase-matching strategies and high-power mixing lasers. However, the reliance on lengthy nonlinear crystals and the necessity for precise phase-matching introduce stringent tolerances on acceptance angles and spectral bandwidths for the interacting fields, thereby constraining its widespread applicability in scientific and industrial domains. This challenge is addressed by combining a broadly tunable ∼5 mW quantum cascade laser operating in the 9.5-12.5 µm range with upconversion detection in ∼100 µm long AGS crystals. Using a tightly focused continuous wave Nd:YVO4 laser with 20 mW output power and spatial filtering of the upconverted beam lead to a SNR of 55 for 50 µs averaging time sufficient for many applications.

Effects of Cutting Planes on Costal Cartilage Warping.

Autogenous costal cartilage becomes a favorable choice for nasal reconstruction and complicated aesthetic rhinoplasty, due to its ample supply, sufficient for most patients. However, a notable drawback is the potential for warping. Our study aims to identify cutting planes that minimize warping. Two hundred and seven costal cartilage grafts were obtained by slicing the extracted costal cartilages from 10 fresh cadavers, along three main planes: cephalocaudal, anteroposterior, and parallel to the synchondrosis plane. Each of these major planes was further divided into grafts taken from both the central and peripheral portions. Furthermore, both subgroups were categorized into three thicknesses: 1mm, 2mm, and 3mm. The warping angles of all grafts were then compared at various time intervals after the initial cutting. Cephalocaudal cuts exhibited significantly greater warping than other planes. Anteroposterior cuts displayed the least warping, although this difference lacked statistical significance. Peak warping occurred at 30 minutes. Certain grafts continued to warp even at 1 month. Central grafts had less warping than peripheral ones, though not statistically significant. Cephalocaudal cuts yielded the highest warping angle. Surgeons seeking thin (< 3 mm) straight grafts should opt for anteroposterior or parallel to synchondrosis planes. Thicker grafts (> 3 mm) can be cut in the cephalocaudal plane with an acceptable warping angle, close to parallel with the synchondrosis plane. For curved cartilage, thin cephalocaudal cut is recommended. Additionally, we suggest placing the cartilage in normal saline for at least 30 minutes, allowing for maximum warping to occur.

Polarization-insensitive wide-angle resonant acousto-optic phase modulator.

Phase modulators are commonly used devices in optics. Free-space phase modulators are typically constructed from optically anisotropic crystals exhibiting the Pockels effect. To preserve the light's polarization state as it propagates through the crystal, it is essential to align the polarization and the angle of incidence of the light with respect to the crystal. In this study, we demonstrate the feasibility of constructing free-space resonant phase modulators with a broad acceptance angle and minimal dependence on the polarization state of light using an acousto-optic approach. These modulators operate in the megahertz frequency range, require modest power levels, have aperture sizes exceeding 1 cm2, and feature sub-millimeter thickness.

A Quality Improvement Project to Measure and Improve the Quality of Below-Knee Ankle Cast Application in Emergency Departments.

Background Ankle fractures are very common injuries seen in an emergency setting. Initial management involves the application of below-knee plaster casts. At our local trauma meetings, we have observed that below-knee casts are often applied incorrectly which can result in suboptimal outcomes for patients and increase the burden on plaster room services if re-application is required. This quality improvement project aimed to assess the quality of below-knee cast applications for ankle fractures in two local district general hospitals (DGHs). Methodology We performed a closed-loop audit utilising a retrospective analysis of patients who underwent casting for unstable ankle fractures. Two audit cycles were completed over a 90-day period across two DGHs. Working within our local orthopaedic unit, we created a targeted, multi-disciplinary educational programme led by experienced plaster technicians. Between audit cycles, we organised a single interactive session with specialist nurses in the urgent treatment centre (UTC) of our DGH while a second DGH did the same with junior doctors working in the emergency department. Both sessions demonstrated correct casting techniques and discussed the importance of a neutral ankle position for optimal patient recovery. Our audit criteria were based on AO Foundation guidance, which states that the ankle should be immobilised in a neutral plantigrade position. All patients with an unstable ankle fracture requiring immobilisation in a below-knee cast were included in the audit. We measured the angle of plantarflexion from neutral, with 90° representing a neutral angle. The angle between the axis of the tibia and the sole of the foot was measured and judged to be within an acceptable range if it was between 80° and 100°, representing a stable ankle position. The audit findings were presented in our local audit meeting. Results In our first audit cycle, we collected data from 65 patients across both sites (N = 32 for DGH 1 and N = 33 for DGH 2). The mean angle was 108.5° and 18 of the 65 (27.7%)patients had angles of ankle plantarflexion that were in the acceptable range (80°-100°). Following the intervention, we again collected data from 61 patients across both sites (N = 28 for DGH 1 and N = 33 for DGH 2). The mean angle was 106.2° and 23 of the 61 (37.7%)patients had an acceptable angle of ankle plantarflexion (80°-100°). Both of our outcome measures showed an improvement but were not statistically significant. The hospital that provided an educational session for the doctors showed an improvement in acceptable ankle casts of 3% while the hospital which provided an educational session for the UTC team improved by 22%. Conclusions We demonstrated a quantifiable approach to assess and improve the quality of below-knee cast application for ankle fractures via a single intervention that would be easily reproducible in other hospitals. We suggest further studies to investigate below-knee cast application quality and its association with patient outcomes as our data and other preliminary sources suggest that current standards are unsatisfactory.

Worse Patient-Reported Outcomes and Spino-Pelvic Parameters After Total Hip Arthroplasty for Rapidly Progressive Osteoarthritis of the Hip Compared to Osteoarthritis: A Propensity-Matched Cohort Study

BackgroundThis study aimed to assess the association between the disease process of hip osteoarthritis and total hip arthroplasty (THA) outcomes; this is a critical issue, as rapid progression has been postulated to be responsible for patient dissatisfaction after THA. MethodsThis retrospective case-control study included 255 patients who underwent THA and completed a mean follow-up duration of 42.1 months (range, 24.0 to 77.0). We classified patients into those who had (n = 26) and did not have (n = 229) rapidly progressive osteoarthritis of the hip (RPOA), defined as a narrowing rate of joint space ≥ 2 mm yearly or a ≥ 50% loss within 12 months, excluding any other cause of a destructive arthropathy. Propensity score-matched cohorts for age, sex, body mass index, and spino-pelvic measures were created, and the outcomes were compared between the 2 groups. ResultsAfter successfully matching RPOA (n = 25) and non-RPOA patients (n = 50), there were significant differences in minimum clinically important difference (P = .009 for European Quality of Life 5-Dimension, and P < .001 for low back pain), patient acceptable symptom state (P = .015 for European Quality of Life 5-Dimension, and P < .001 for Hip Disability and Osteoarthritis Outcome Score Joint Replacement score), patient satisfaction (P = .028), and T1 pelvic angle as an indicator of global sagittal spinal deformity (P = .017). There was a correlation between T1 pelvic angle and low back pain in the RPOA group (R = 0.628, P < .001). ConclusionsPatients who exhibited RPOA before undergoing THA showed worse patient-reported outcomes compared with those who did not have rapid progression. Our study highlights the critical role of the disease process in influencing THA outcomes, advocating for a paradigm shift toward more meticulous preoperative evaluations, including global spinal deformity, standardized diagnostic criteria, and tailored interventions.

Use of planar retarding field to improve energy resolution of projection-type electron spectroscopy collimator analyzer

A method to improve the energy resolution of the recently proposed projection-type electron spectroscopy collimator analyzer (PESCATORA) is presented. PESCATORA is a simple, highly compact two-dimensional electron analyzer with a wide acceptance angle of up to ±60°. The use of a combined planar retarding field and parallel-hole collimator (PRF–PHC) as a band-pass filter is analytically and numerically studied. In PESCATORA, a parallel-hole collimator placed behind a specially designed electrostatic collimator lens is used as a band-pass filter to obtain energy-resolved angular distributions of emitted or diffracted electrons (or charged particles) from sample surfaces. The PRF–PHC system can be introduced in PESCATORA by simply adding a planar grid in front of the collimator plate. This allows the transmittance and energy resolution to be effectively controlled by only changing the retarding voltage of PRF, consequently improving PESCATORA. Moreover, an improved PESCATORA instrument with the highest possible specifications is presented.

Radiological Differences Following Proximal Femoral Nail Antirotation (PFNA) Compared to the Contralateral Side and Its Correlation with Harris Hip Score (HHS) in Intertrochanteric Femoral Fracture After Three Months

Introduction: The incidence of intertrochanteric femoral fractures, which account for 50% of all hip fractures, is increasing as a result of the aging population. While PFNA surgery typically enhances outcomes, certain individuals continue to have pain, stiffness, and difficulties with their gait. This study aims to determine whether there is a correlation between post-surgical complications and changes in hip joint angles assessed three months following PFNA to lead future advances in PFNA surgery for older persons by comparing impacted and unaffected hips and correlating angles with patients' hip ratings. Methods: This study included 42 individuals who underwent surgery for intertrochanteric fractures aged 50 and above. Eligible participants must possess the ability to walk before to the study, have no history of previous leg fractures, and be capable of participating in rehabilitation. Individuals having comorbidities impacting these aspects or those unable to partake were not included. Result : This study looked at hip angles in 42 people who had surgery intertrochanteric fracture. While the participants varied in age and gender, the surgery itself didn't seem to significantly change the angles of their hip bones or their ability to walk. This suggests that PFNA may not directly affect hip mechanics on its own. Conclusion: This study indicates that attaining acceptable hip angles during the procedure could enhance patients' mobility and post-operative condition. Further investigation involving bigger cohorts and extended periods of observation is necessary to validate these findings and ascertain whether modifying these angles during surgery will result in improved outcomes following PFNA. Keywords: Intertrochanteric fracture; Hip fracture; PFNA

The Effects of Target Thicknesses and Backing Materials on a Ti-Cu Collision Weld Interface Using Laser Impact Welding

This study demonstrates that the thickness of the target and its backing condition have a powerful effect on the development of a wave structure in impact welds. Conventional theories and experiments related to impact welds show that the impact angle and speed of the flyer have a controlling influence on the development of wave structure and jetting. These results imply that control of reflected stress waves can be effectively used to optimize welding conditions and expand the range of acceptable collision angle and speed for good welding. Impact welding and laser impact welding are a class of processes that can create solid-state welds, permitting the formation of strong and tough welds without the creation of significant heat affected zones, and can avoid the gross formation of intermetallic in dissimilar metal pairs. This study examined small-scale impact using a consistent launch condition for a 127 µm commercially pure titanium flyer impacted against commercially pure copper target with thicknesses between 127 µm and 1000 µm. Steel and acrylic backing layers were placed behind the target to change wave reflection characteristics. The launch conditions produced normal collision at about 900 m/s at the weld center, with decreasing impact speed and increasing angle moving toward the outer perimeter. The target thickness had a large effect on wave morphology, with the wave amplitude increasing with target thickness in both cases, peaking when target thickness is about twice flyer thickness, and then falling. The acrylic backing showed a consistently smaller unwelded central zone, indicating that impact welding is possible at a smaller angle in that case. Strength was measured in destructive tensile testing. Failure was controlled by the breakdown of the weaker of the two base metals over all thicknesses and backings. This demonstrates that laser impact welding is a robust method for joining dissimilar metals over a range of thicknesses.

Design and development of a novel and cost effective modified Compound parabolic trough collector

In the context of achieving Net Zero targets, the adoption of compound parabolic concentrator (CPC) technology can play a vital role. The purpose of this work is to modify the design of a conventional CPC in such a way that for the same concentration ratio, and for same aperture area, the modified CPC (MCPC) will require significantly less material for its support structure, receiver and reflector: and hence will have reduced cost. The MCPC, we designed, has a concentration ratio of 4 and an acceptance angle 10° and requires position modification only once a month when oriented with its long axis along the East-West direction. We report experiments on an experimental prototype: the solar-to-thermal efficiency of which was 35.7% and cost of which was below $60/m2. This MCPC enables inexpensive and convenient generation of heat applications including driving low temperature industrial process heating, generation of hot water, hot air for drying, space-heating and even cooking. This can directly contribute to meeting Net Zero goals and furthermore address the problem of deforestation due to use of wood for domestic cooking. Also, since the MCPC can be manufactured using technologies available even in semi-urban regions of the Sun-belt, use of the MCPC can also boost local manufacturing economies providing dignified employment opportunities in currently underserved parts of the world.

Photopolymer Holographic Lenses for Solar Energy Applications: A Review.

Holographic lenses (HLs) are part of holographic optical elements (HOE), and are being applied to concentrate solar energy on a focal point or focal line. In this way, the concentrated energy can be converted into electrical or thermal energy by means of a photovoltaic cell or a thermal absorber tube. HLs are able to passively track the apparent motion of the sun with a high acceptance angle, allowing tracking motors to be replaced, thus reducing the cost of support structures. This article focuses on a review of the materials used in the recording of a holographic lens (HL) or multiple HLs in photovoltaic and/or concentrating solar collectors. This review shows that the use of photopolymers for the recording of HLs enables high-performance efficiency in physical systems designed for energy transformation, and presents some important elements to be taken into account for future designs, especially those related to the characteristics of the HL recording materials. Finally, the article outlines future recommendations, emphasizing potential research opportunities and challenges for researchers entering the field of HL-based concentrating solar photovoltaic and/or concentrating solar thermal collectors.

Nested design and numerical simulation of ellipsoidal glass tube X-ray lens

This paper presents a nested optimization design scheme for ellipsoidal glass tubes. The lens, also known as a mirror, is composed of multiple ellipsoidal glass tubes with varying semi-major and semi-minor axes, nested within a larger-diameter ellipsoidal glass tube. Compared to Traditional Ellipsoidal Single-bounce Lens (TESL), the Nested Ellipsoidal Glass Tube X-ray Lens (NEXL) can utilize a smaller or even no beam stop at its input, mitigating the impact of the direct X-ray beam on the NEXL's focused beam and thereby enhancing X-ray source utilization. NEXLs can be designed with a large input focal distance, making them suitable for synchrotron radiation X-ray sources located significant distances from the source point to the sample. Simulation results show that for a synchrotron X-ray source 34,000 mm from the sample, a NEXL with six ellipsoidal sub-tubes offers a solid acceptance angle four times greater than a single ellipsoidal glass tube lens. Furthermore, for standard laboratory X-ray sources, a NEXL with three sub-tubes provides double the solid acceptance angle compared to a single-tube lens. These features position NEXLs as highly versatile in the field of X-ray technology.

The Long-Term Efficacy of Computed Tomography-Navigated Total Hip Arthroplasty: An 18-Year Follow-Up Study.

We retrospectively reviewed 145 consecutive CT-navigated THAs for >15 years. We surveyed the angles placed in both the acetabular and femoral components, survivorship, the occurrence of dislocation, the revision rate, and the fixation grade of the acetabular component. The mean follow-up duration was 18.4 years. Overall, 73.8% of THAs were within the safe zone of Lewinnek. There were four dislocations (2.8%), with three occurring within 1 month after surgery and the other within 7 years after surgery. Revision THA was performed in one case (0.69%); consequently, the survival rate was 99.3%. The fixation grade was evaluated in 144 hips, and those were evaluated as having "no loosening". CT-navigated THA was speculated to contribute to long-term survivorship, with a low rate of loosening, even after 18 years of follow-up. It was speculated that the acetabular component was placed at an acceptable insertion angle and a suitable position for stable initial fixation.

Broadband Ag/SiO2/Fe/TiO2 ultrathin planar absorber with a wide acceptance angle from visible to near-infrared regions

We present theoretical and experimental evidences of a broadband ultrathin optical absorber, constructed using Ag(85 nm)/SiO2(70 nm)/Fe(13 nm)/TiO2(60 nm) planar films, with a wide acceptance angle and effective admittance similar to that of air. Calculations show that this system displays near-complete visible to near-infrared absorption owing to admittance matching. The electromagnetic distribution within the layered film reveals that the high absorption rate is primarily attributed to the deep subwavelength Fe film. Maximum absorption of 99.3% is achieved even with a 13-nm-thick Fe absorptive film, and an average absorption rate of 94.8% is observed in the 400–1100 nm wavelength range. Notably, even at 60° oblique incidence, the fabricated absorber sustains an absorption rate of 85.4% (for unpolarized light). Such absorbers can be applied to efficient thermal generation and various other applications owing to their minimal heat capacity, expansive area, and fabrication simplicity.

Design and Optical Performance Evaluation of the Three-Dimensional Solar Concentrators with Multiple Compound Parabolic Profiles and Elliptical and Rectangular Receiver Shapes

The compound parabolic concentrator (CPC) is a core technology in the field of solar concentration. Nevertheless, it only has one degree of freedom in the choice of its half-acceptance angle. In this study, extending the idea of the three-dimensional CPC, a design method for new kinds of concentrators having a CPC shape at each profile with various acceptance angles in all directions is proposed. The feature of this method is that the receiver can take any shape. Here, elliptical and rectangular receivers are assumed, and the shape and concentration performance of the concentrators with multiple CPC profiles and an elliptical receiver (MultiPro-ECPCs) and the concentrators with multiple CPC profiles and a rectangular receiver (MultiPro-RCPCs) are derived. The new designs are compared to the conventional CPC and a mirrorless flat receiver through ray-tracing simulations in terms of energy distribution on the receiver, optical efficiency, and optical concentration ratio based on axial and solar angles. The results show that in terms of optical efficiency, the MultiPro-RCPCs cover a wider range of incident angles after the 3DCPC. In terms of the optical concentration ratio, the MultiPro-ECPC with a longitudinal half-acceptance angle of 15° has the highest peak value of 19.5, followed by the MultiPro-RCPC. This study enlightens that with the concentration system settings adapted to the acceptance range of the proposed concentrators, a higher concentration can be achieved with the MultiPro-ECPC and MultiPro-RCPC compared to the conventional CPC.

Effect of Acceptance angle on the design and performance of a heat pipe based compound parabolic collector at Kano, Nigeria

The performance of any solar collector depends on the solar radiation available, its design and orientation. The aim of this work is to develop a compound parabolic solar collector (CPC) and optimize its performance for domestic use under climatic condition of Kano, Nigeria (Φ =12.05 o N). The acceptance angle plays an important role in determining the solar radiation acceptance of the CPC collector. Therefore this paper investigates the effect of the acceptance angle on the CPC design, solar radiation collection and absorption by the heat pipe receiver installed inside the CPC collector. From the radiation data and the analysis used, this study shows that as the acceptance angle increases, the collector height decreases and the concentration ratio increases.

Advancements in Fresnel Lens Technology across Diverse Solar Energy Applications: A Comprehensive Review

Concentration of solar energy may be obtained by reflection, refraction, or a combination of the two. The collectors of a reflection system are designed to concentrate the sun’s rays onto a photovoltaic cell or steam tube. Refractive lenses concentrate light by having it travel through the lens. The sun’s rays are partially reflected and then refracted via a hybrid technique. Hybrid focus techniques have the potential to maximize power output. Fresnel lenses are an efficient tool for concentrating solar energy, which may then be used in a variety of applications. Development of both imaging and non-imaging devices is occurring at this time. Larger acceptance angles, better concentration ratios with less volume and shorter focal length, greater optical efficiency, etc., are only some of the advantages of non-imaging systems over imaging ones. This study encompasses numerical, experimental, and numerical and experimental studies on the use of Fresnel lenses in various solar energy systems to present a comprehensive picture of current scientific achievements in this field. The framework, design criteria, progress, and difficulties are all dissected in detail. Accordingly, some recommendations for further studies are suggested.

A refined analytical model for reconstruction problems in diffuse reflectance spectroscopy

A refined analytical model of spatially resolved diffuse reflectance with small source-detector separations (SDSs) for the in vivo skin studies is proposed. Compared to the conventional model developed by Farrell et al., it accounts for the limited acceptance angle of the detector fiber. The refined model is validated in the wide range of optical parameters by Monte Carlo simulations of skin diffuse reflectance at SDSs of units of mm. Cases of uniform dermis and two-layered epidermis-dermis structures are studied. Higher accuracy of the refined model compared to the conventional one is demonstrated in the separate, constraint-free reconstruction of absorption and reduced scattering spectra of uniform dermis from the Monte Carlo simulated data. In the case of epidermis-dermis geometry, the recovered values of reduced scattering in dermis are overestimated and the recovered values of absorption are underestimated for both analytical models. Presumably, in the presence of a thin mismatched topical layer, only the effective attenuation coefficient of the bottom layer can be accurately recovered using a diffusion theory-based analytical model while separate reconstruction of absorption and reduced scattering fails due to the inapplicability of the method of images. These findings require implementation of more sophisticated models of light transfer in inhomogeneous media in the recovery algorithms.

Building-Integrated Concentrating Photovoltaics based on a low-toxicity photopolymer

Low-toxicity solar concentrator systems represent an important challenge for outstanding photovoltaic (PV) applications. Particularly, multiplexed holographic lenses (MHL) as Holographic Solar Concentrators (HSC) provide insight into promising possibilities for Building-Integrated Concentrating PVs. This technology does not affect crucial ecosystems, and can convert buildings from energy consumers into energy suppliers. They can be used in windows, roofs, or walls, and a high diffraction efficiency and wide acceptance angle are desired. In this work, we presented several designs of MHL of low spatial frequency 525 lines mm−1, based on a low-toxicity photopolymer and supported on a window glass. The average diffraction efficiency of these HSC was evaluated at 633 nm, whereas the acceptance angle was evaluated by measuring the short-circuit current under solar illumination at different incident angles. Versatile and high-efficiency holographic elements have been used to concentrate sunlight from different relative positions during the day, avoiding the need for expensive tracking systems. To the best of our knowledge, this is the best trade-off between high diffraction efficiency (85 % ) and wide acceptance angle (104∘) in a low-toxicity holographic solar concentrator.