Operating Region Research Articles

Fuzzy Gain Scheduling of the Fractional-Order PID Controller for a Continuous Stirred-Tank Reactor Process

In most chemical industries, continuous stirred-tank reactors (CSTRs) are essential for the production of chemicals. The CSTR process is highly nonlinear and has both stable and unstable equilibrium points. Control system engineers face a difficult issue when designing a single controller for temperature control in both stable and unstable areas. Due to these problems, implementing the conventional proportional-integral-derivative (PID) controller may lead to instability in controlled variables. Therefore, in this paper, the entire operating region is divided into three regions. The fractional-order PID controller as a local controller is designed in each operating region to control the temperature, and its parameters are tuned with a genetic algorithm by minimizing the integral of absolute error and control input change with a weighting factor. Then, a fuzzy gain scheduling scheme based on the Tagaki-Sugno fuzzy model is used to properly interpolate the outputs of the local controllers. A set of simulations are carried out to demonstrate the effectiveness of the proposed controller, and its performance is compared with that of an adaptive nonlinear controller and fuzzy gain scheduling of the PID controller.

Open-Loop Control Co-Design of Semisubmersible Floating Offshore Wind Turbines Using Linear Parameter-Varying Models

Abstract This paper discusses a framework to design elements of the plant and control systems for floating offshore wind turbines in an integrated manner using linear parameter-varying models. Multiple linearized models derived from aero-elastic simulation software in different operating regions characterized by the incoming wind speed are combined to construct an approximate low-fidelity model of the system. The combined model is then used to generate open-loop, optimal control trajectories as part of a nested control co-design strategy that explores the system’s power production and stability using the platform pitch tilt as a proxy in the context of crucial plant and control design decisions. The radial distance between the central and outer columns and the diameter of the outer columns of the semisubmersible platform are the plant design variables. The platform stability and power production are studied for different plant design decisions. The effect of plant decisions on subsequent power production and stability response of the floating wind turbine is quantified in terms of the levelized cost of energy. The results show that the inner-loop constraints and the plant design decisions affect the turbine’s power and, subsequently, the cost of the system.

A region-based low-carbon operation analysis method for integrated electricity-hydrogen-gas systems

A region-based low-carbon operation analysis method for integrated electricity‑hydrogen-gas systems (IEHGSs) is proposed in this paper. The committed carbon emission operation region (CCE_OR) and the economic CCE_OR (ECCE_OR) are proposed to evaluate the low-carbon feasible space (LCFS) from the low-carbon, secure, and economic perspectives, which provides powerful tools for the low-carbon operation analyses of IEHGSs. Firstly, a coordinated mechanism of carbon flow and hydrogen flow is developed to excavate the low-carbon operation potential of IEHGSs. Then, based on the distributionally robust chance-constrained approach, the concepts and models of CCE_OR and ECCE_OR are defined and formulated considering uncertainties and hydrogen merits. Furthermore, a region model reformulation method is proposed to reformulate the uncertain and non-convex CCE_OR and ECCE_OR models into the deterministic and mixed-integer linear region models. The geometric properties of CCE_OR and ECCE_OR are both theoretically proven, which are the union set of finite convex and bounded polytopes. The united region solution methodology considering the geometric properties of CCE_OR and ECCE_OR is presented to effectively characterize CCE_OR and ECCE_OR. Finally, the numerical results on two test systems verify the effectiveness and applicability of the proposed methods. Simulation results indicate that the proposed methods can improve the LCFS, characterize visual coupling relationships between LCFS and observation variables, and provide comprehensive low-carbon operation information of operation points.

TRNSYS MODEL OF THE COMBI BOILER DOMESTIC HOT WATER CIRCUIT WITH A FOCUS ON THE PARAMETER DEFINITION OF THE PLATE HEAT EXCHANGER

Combi boilers used for both space and domestic hot water heating are one of the common household appliances. Modelling the domestic hot water circuit of a combi boiler for the preliminary evaluation of the laboratory testing is of crucial importance since it decreases the time, cost, and energy spent on the trials. There are various modelling approaches established by the authors of this paper. Domestic hot water circuit of the appliance is modelled previously making use of the Transient System Simulation Tool (TRNSYS 18) and a good agreement is achieved with the experimental and numerical data for the economic mode simulations. The drawback of the current TRNSYS model is the dependence on the experimental data for some of the parameter definitions of the components selected from the TRNSYS library, i.e. UA (multiplication of the overall heat transfer coefficient and the heat transfer area) input of the plate heat exchanger and heat retention effect of the heat cell block. In this paper, a constant value is assigned to the parameter definition of UA instead of a time dependent varied profile. Mean absolute errors covering the steady-state and transient operating regions for the domestic hot water inlet and outlet temperature difference in economic mode simulations stay nearly the same around 0,46°C, 0,82°C, and 0,53°C for 5 l/min, 7 l/min, and 8,7 l/min, respectively, under constant and variable UA approaches. Comfort operating scheme model is established with a couple of experimental data as of the principal application of the constant UA approach. Mean absolute error of the overall domestic hot water inlet and outlet temperature difference profile decreases to 0,5°C in the comfort mode simulation.

Efficient waste heat recovery from molten carbonate fuel cells through graphene-collector thermionic generators

The waste heat released by molten carbonate fuel cells (MCFCs) contains considerable energy that can be captured for electric power generation. Nonetheless, the current high-grade heat harvesting devices for the MCFC cogeneration of electrical power are still constrained by low power output or energy conversion. To address this challenge, we present a novel hybrid system that combines an MCFC and a graphene-collector thermionic generator (GCTG), in which the GCTG can efficiently harness the exhaust heat released from the MCFC and generate additional electricity. The results show that the hybrid system’s maximum power density reaches 0.298 W/cm2, which is 1.6 times that of the sole MCFC at 923 K, demonstrating that the hybrid system delivers a significant boost in output performance. Furthermore, finite-time thermodynamics estimates the hybrid system’s optimal operating regions and key parameter designs. The optimal performance of the hybrid system can be further improved by selecting the optimal area ratio, raising the MCFC operating temperature, strengthening the heat transfer coefficient, lowering the thermal emissivity of the thermionic emitter, and manufacturing the perfect optical reflector. The MCFC-GCTG outperforms other MCFC-based hybrid systems regarding output performance, demonstrating that GCTG can more effectively exploit the waste heat released from MCFCs than other heat recovery devices. This study offers valuable theoretical guidance for the strategic optimization of the MCFC-GCTG hybrid system, thereby paving a constructive strategy towards realizing advanced, high-performance MCFC cogeneration systems.

Operational envelope for planning cold flow production

The paper presents a method to determine an operational envelope for the cold flow technology with respect to producing gas–oil ratio (GOR) and water cut (WC). The cold flow technology is a flow assurance method that enables cold production flow in thermal equilibrium with the seabed temperature. Cold flow converts hydrate and wax into dry, non-plugging microparticles inside a subsea cold flow unit downstream the wellhead. The small particles travel along with the liquid in the form of a slurry to the receiving host. The operational envelope shows that if the production flow reaches certain combinations of GOR and Wc, the hydrate volume fraction in liquid and consequently the slurry’s effective viscosity could be too high for pipe transportation. This paper also investigates the case when the slurry is transported with remaining water, where there might be some emulsion phenomena. Results show that this could reduce the operational region of the cold flow envelope, particularly for GOR–Wc values around the inversion point volume fraction. Therefore, water–slurry emulsification should also be taken into consideration when considering the operational envelope. If the hydrate–oil mixture is found to be too viscous to transport it can be resolved by, for example, removing water from the production flow upstream the cold flow unit. GOR–WC profiles from a real field case are over-imposed on the operational envelope to see the development during the field lifetime. Tieback costs for the cold flow technology are found to be 20–30% less than conventional methods for a 100 km tieback. The relative cost reduction increases with increasing tieback distance.

Tunable microwave frequency comb generation via periodic relaxation oscillation in directly modulated laser

In this paper, a novel and simple generation scheme based on a directly modulated laser (DML) is proposed for tunable microwave frequency combs (MFCs). When the input modulated RF power is intentionally controlled to be sufficiently high to drive the DML into its nonlinear operating region periodically, relaxation oscillations will be excited in the same period. The modulated light from the DML is subsequently detected by a photodetector, and a special kind of microwave signal source can be optically produced and shows up in the form of MFC in the frequency domain. In the proof-of-concept experiment, tunable MFCs are demonstrated with the bandwidth of more than 25 GHz, the comb spacing of 0.5 ∼ 3 GHz, and the flatness of less than ± 2 dB with the frequency from 3 GHz to 18 GHz. The bandwidth of the generated MFC is in accordance with the relaxation oscillation frequency of the DML. The comb spacing is strictly equal to the frequency of the modulated RF signal and thus flexibly adjustable. The carrier-to-noise ratio can be up to 48 dB, and the single-sideband phase noise is measured to be lower than − 90 dBc/Hz@1 kHz for MFCs with comb spacings of 0.7 ∼ 3 GHz.

Implementation of analytical quality by design concepts for the optimization of quantitative 1H nuclear magnetic resonance (1H-qNMR) method for quantitation of novel anti-covid drugs (molnupiravir and favipiravir) in their pharmaceutical dosage forms

For the first time in the literature, the Analytical Quality by Design (AQbD) principles were applied to the development of a specific and simple quantitative proton nuclear magnetic resonance (1H-qNMR) method for quantitation of two antiviral drugs, molnupiravir (MOL) and favipiravir (FAV). This 1H-qNMR method was developed within the QbD framework, the new paradigm of quality recently outlined in the ICH Q14 guidelines. Basic principles of AQbD have been adapted starting with early risk assessment and identification of the analytical target profile (ATP), the analytical procedure attributes (APA) and the analytical procedure parameters (APPs). During the scouting phase, dimethyl sulfoxide-d6 (DMSO‑d6) was selected as the deuterated solvent and maleic acid as the internal standard. The quantitative determination was based on the selective proton signals from MOL's pyrimidine ring at 6.82 ppm (doublet) and FAV's hydroxyl group at 8.71 ppm (singlet), as well as a singlet signal from the IS at 6.24 ppm. A Box-Behnken Design was employed in response surface methodology to develop mathematical predictive models relating the APPs to the APAs followed by multicriteria- decision making with the aid of Derringer's desirability function. Finally, the method operable design regions (MODRs) were computed with the aid of Monte Carlo simulations and identified as the multidimensional combination of the APPs where the risk of failure to fulfill the requirements for the APAs was lower than 5 %. The most robust NMR conditions for MOL, with MODR intervals in brackets, were as follows: no. of scans of 72 (16–124.4), a relaxation delay of 19.8 s (1.2–40 s) and an acquisition time of 3.98 s (2.1–6 s). Similarly, for FAV NMR quantitation, the most robust conditions were found to be 72 scans (16–117.3), a relaxation delay of 19.8 s (1.4–40 s) and an acquisition time of 3.98 s (2.2–6 s). The developed method was validated in accordance with the recently endorsed ICH Q2R2 guidelines, and it exhibited detection limits of 1.04 and 0.88 mg mL−1, as well as quantitation limits of 3.45 and 2.95 mg mL−1 for MOL and FAV, respectively. The method was successfully applied to the analysis of the studied analytes in their pharmaceutical products, proving to be simple, fast, non-destructive, and accurate. Additionally, it can be considered an environmentally friendly alternative for quantitation and quality control analysis of pharmaceutical products.

Performance evaluation of a thermoradiative device coupled to a solid oxide fuel cell

To improve the efficiency of the energy conversion, a novel coupling model comprising a solid oxide fuel cell (SOFC), a thermoradiative cell (TRC) with sub-bandgap and non-radiative losses, and a regenerator is proposed. The waste heat from the SOFC is utilized by the TRC to produce extra power. Considering the main irreversible losses inside the coupling model, mathematical expressions for power and efficiency are derived, along with revealing the performance characteristics. Numerical calculation results illustrate that the maximum power output density (MPOD) and corresponding efficiency of the coupled model are 0.94 Wm−2 and 41%, respectively, which are improved by 68% and 14%, respectively, compared to a single SOFC. Furthermore, the influences of parameters such as non-radiative losses, temperature, and bandgap are investigated. The optimal operating regions for power output density, efficiency, and current are determined. Finally, compared with the MPODs of the SOFC-based coupled models, the SOFC-TRC can more effectively utilize the waste heat released from the SOFC. This study may provide some new ideas for the waste heat utilization of SOFC.

Prediction of gold mineralization zones using spatial techniques and geophysical data: A case study of the Josephine prospecting licence, NW Ghana

In this study, predictive models that characterize gold potential zones within the Josephine Prospecting Licence (PL) Area of Northwestern Ghana have been created by data-driven methods comprising frequency ratio and information value. These predictive models were evaluated using known locations of gold (Au) occurrence datasets and compared to each other. The mineral prospectivity models (MPMs) of gold occurrence areas within the Josephine PL Area were constructed by determining the spatial correlation between known locations of Au occurrences and eight mineralization related factors. The locations of these known Au occurrences, which characterize regions of anomalously high Au geochemical concentration and regions of previous or ongoing artisanal mining operations were identified by using geographic positioning systems (GPS). Eight mineralization related factors (geoscientific thematic layers) over the entire study area composed of analytic signal, lineament density, uranium-thorium ratio, uranium, potassium-thorium ratio, potassium, reduction-to-equator and geology were used to generate the MPMs. The predictive capacity of each of the MPMs generated was determined by employing the area under the receiver operating characteristics curve (AUC). The AUC score obtained for the predictive models produced based on the information value and the frequency ratio approaches were respectively 0.794 and 0.815. The AUC scores generated indicate that the MPMs produced are good predictive models (with an AUC greater than 0.7) and can therefore assist in narrowing down the highly prospective zones of mineral occurrences within the study area. However, the overall predictive potential of the frequency ratio approach was better than the model produced by the information value approach.

Spin Hall Switching Enabled by Uniaxial In-Plane Magnetocrystalline Anisotropy

We present a new method for stabilization of magnetic devices: in-plane uniaxial magnetocrystalline anisotropy, achieved through epitaxial growth of a magnetic thin film on a single-crystal substrate. This paradigm enables the creation of in-plane spin orbit torque magnetic random access memory (SOT-MRAM) devices that function without external fields and exhibit the same scalability as perpendicular SOT-MRAM. Through theoretical derivations and numerical simulations based on the Landau-Lifshitz-Gilbert (LLG) equation with spin transfer torque, we show that switching of such devices can be optimized by varying the angle between the injected spin current and the crystalline easy axis, and contrast this angular dependence with the Stoner-Wohlfarth model. Furthermore, we demonstrate rich and complex magnetization dynamics in this system, including strong and tunable dependence on bulk and interfacial magnetoresistance and boundaries between stochastic and deterministic switching. Finally, we present a concept that couples our in-plane anisotropy layer with an out-of-plane ferromagnet to achieve out-of-plane field-free SOT-MRAM switching. We quantify regions of operation for this new device and link them to simulation results for the in-plane layer alone.

Balancing of four wire loads using linearized H-bridge static synchronous compensators

<p>In this paper, a load balancing system is designed to balance the secondary phase currents of 11 kV/380 V, 50 Hz, 100 kVA power transformer in a three phase 4-wire, distribution network. The load balancing system is built of six identical modified static synchronous compensators (M-STATCOMs). Each M-STATCOM is constructed of a voltage source converter-based H-bridge controlled in capacitive and inductive modes as a linear compensating susceptance. The M-STATCOM current is controlled by varying its angle such that it exchanges pure reactive current with the utility grid. Three identical M-STATCOMs are connected in delta-form to balance the active phase currents of the power transformer, whereas the other three identical M-STATCOMs are connected in star-form to compensate for reactive currents. The M-STATCOMs in the delta-connected compensator are driven by 380 V line-to-line voltages, whilst, those connected in star-form are driven by 220 V phase voltages. The results of the 220 V and 380 V M-STATCOMs have exhibited linear and continuous control in capacitive and inductive regions of operation without steady-state harmonics. The proposed load balancing system has offered high flexibility during treating moderate and severe load unbalance conditions. It can involve any load unbalance within the power transformer current rating and even unbalance cases beyond the power transformer current rating.<strong></strong></p>

Linear Quadratic Optimal Robust Multivariable Proportional-Integral Control Design for a Boiler-Turbine Unit

Abstract Boiler-turbine unit is a highly nonlinear, coupled, and ill-conditioned system. Moreover, the presence of physical constraints, such as actuator magnitude and rate limits, makes the system difficult to control. This paper employs a fixed multivariable proportional-integral (PI) controller of the I–P structure for robust linear quadratic (LQ) compensation of a nonlinear boiler-turbine benchmark. In order to ensure that a single PI controller works for the whole operating region of this nonlinear system, the linearized model of the system is represented as a norm-bounded, time-varying uncertain system. The ranges of the uncertain parameters of this linearized model are determined from different operating points of the nonlinear system. To design the PI controller for the uncertain system, first, it is transformed into a state feedback design for an augmented uncertain system and then the state feedback gains satisfying some LQ performance limit are computed by solving a linear matrix inequality (LMI) problem. As the uncertainty in the feedforward matrix of the linearized model cannot be considered in the above design process, an LMI-based method is developed to check if the designed PI controller performance in H∞ sense is close to the one if the neglected uncertainty is included. The performance of the controller is tested on the nonlinear boiler-turbine unit under several operating conditions and physical constraints. Comparisons are also made with some existing PI controllers, to show the superiority of the proposed robust PI controller.

Nonlinear analysis of coupled neutronic-thermohydraulic stability characteristics of supercritical water-cooled reactor

The Supercritical Water-Cooled Reactor (SCWR) exhibits significant changes in thermophysical properties of the coolant, but its dynamic characteristics are different from existing reactors, due to the supercritical conditions of the coolant. This necessitates the study of the stability behaviour of SCWR, which requires a dynamic model of the reactor. In this work, a simple unsteady lumped parameter model (LPM) for SCWR has been developed. The LPM includes point reactor kinetics for neutron balance and a two-region model for fuel and coolant thermal hydraulics. The two regions are separated from each other by a boundary that depends on the pseudocritical temperature of the coolant. Regions of stable and unstable operation are identified in the parameter space by linear stability analysis. Bifurcation analysis is carried out to capture the non-linear dynamics of the system. Generalised Hopf (GH) points are located, and parameter ranges for supercritical (soft and safe) and subcritical (hard and dangerous) Hopf bifurcation are identified. The type of transient behaviour of the system for finite (though small) perturbations is predicted based on this analysis. The existence of predicted limit cycles is confirmed by numerical simulation of the nonlinear ODEs, using the shooting technique in case of unstable limit cycles. Furthermore, the effects of geometric, control and neutronics parameters on the stability of the system are studied.

Assessment of Data Capture Conditions Effect on Reverse Electrodialysis Process Using a DC Electronic Load

Reverse electrodialysis (RED), an emerging membrane-based technology, harnesses salinity gradient energy for sustainable power generation. Accurate characterization of electrical parameters in RED stacks is crucial to monitoring its performance and exploring possible applications. In this study, a DC electronic load module (DCELM) is implemented in a constant current condition (CC mode) for characterization of lab scale RED process, using a RED prototype in-house designed and manufactured (RU1), at different data capture setups (DCS), on which the total number of steps for data capture (NS) and the number of measurements per step (ρ) are the parameters that were modified to study their effect on obtained electrical parameters in RED. NS of 10, 50, and 100 and ρ of 10 and 20 were used with this purpose. The accuracy of resulting current and voltage steps can be enhanced by increasing NS and ρ values, and according to obtained results, the higher accuracy of resulting output current and voltage steps, with low uncertainty of the average output steps (AOS) inside the operational region of power curve, was obtained using a DCS of NS = 100 and ρ = 20. The developed DCELM is a low-cost alternative to commercial electronic load devices, and the proposed methodology in this study represents an adaptative and optimizable CC mode characterization of RED process. The results obtained in this study suggest that data capture conditions have a direct influence of RED performance, and the accuracy of electrical parameters can be improved by optimizing the DCS parameters, according to the required specifications and the scale of RED prototypes.

Machine Learning Algorithms for Semi-Autogenous Grinding Mill Operational Regions’ Identification

Energy consumption represents a significant operating expense in the mining and minerals industry. Grinding accounts for more than half of the mining sector’s total energy usage, where the semi-autogenous grinding (SAG) circuits are one of the main components. The implementation of control and automation strategies that can achieve production objectives along with energy efficiency is a common goal in concentrator plants. However, designing such controls requires a proper understanding of process dynamics, which are highly complex, coupled, and have non-deterministic components. This complex and non-deterministic nature makes it difficult maintain a set-point for control purposes, and hence operations focus on an optimal control region, which is defined in terms of desirable behavior. This paper investigates the feasibility of employing machine learning models to delineate distinct operational regions within in an SAG mill that can be used in advanced process control implementations to enhance productivity or energy efficiency. For this purpose, two approaches, namely k-means and self-organizing maps, were evaluated. Our results show that it is possible to identify operational regions delimited as clusters with consistent results.

Method operable design region for robust RP-HPLC analysis of pioglitazone hydrochloride and teneligliptin hydrobromide hydrate: incorporating hybrid principles of white analytical chemistry and design of experiments

BackgroundA combination of pioglitazone hydrochloride with teneligliptin hydrobromide hydrate is used to treat type-2 diabetes. Several chromatographic techniques have been described in the literature for determination of each of these medications separately. But these procedures used organic solvents that could be dangerous for humans and animals, not to mention harmful to the environment. It is vital to substitute or reduce the use of these neurotoxic and teratogenic solvents in the chromatographic analysis of these anti-diabetic medications to ensure the safety of life and safeguard the environment. The chromatographic technique used for sample analysis should have characteristics like robustness, eco-friendliness, cost-effectiveness, and user-friendliness following the recently developed idea of white analytical chemistry. Teneligliptin and pioglitazone have not yet been simultaneously estimated using a chromatographic method that has been documented in the literature.MethodsA white analytical chemistry-assisted RP-HPLC method has been developed to fill this gap, using economical and eco-friendly solvents. The design of the experiment approach was used during the development of the RP-HPLC method to reduce organic waste and guarantee that the procedure complied with all applicable regulations. Response surface models were built using the full factorial design approach, and the analytical design space was investigated. This method allowed for the identification of an optimal chromatographic condition within the method's operational design region, allowing reliable RP-HPLC analysis of pioglitazone and teneligliptin.ResultsThe developed RP-HPLC technique underwent validation and was used effectively to assess these drugs in their fixed-dose combinations. Assessments were made of the suggested and published RP-HPLC techniques' validation status, process greenness, cost, and analysis time. For a thorough examination, this review included white analytical chemistry-based RGB models and different green analytical chemistry-based tools.ConclusionIn allowing the simultaneous estimate of teneligliptin and pioglitazone, the devised approach demonstrated robustness, eco-friendliness, and cost-effectiveness.

Modeling and design of high-sensitivity dual optical feedback interferometry measurement system enhanced by period-one dynamics

Laser optical feedback interferometry (OFI) is a unique one-channel interferometric measurement technology with the advantages of compact structure, low implementation cost and easy alignment. However, it has a critical challenge that the visibility of interference fringe is often low and further induces low measurement sensitivity, especially in occasions when the optical feedback strength is feeble, e.g., biomedical and fluid detection. Recently, it has been demonstrated that period-one (P1) dynamics can enhance the measurement sensitivity by introducing extra optical feedback to form a dual optical feedback interferometry (DOFI) system. However, the details of the enhancement mechanism and how to design such a system are still required to unveil. In this paper, comprehensive discussions of designing a DOFI system with high measurement sensitivity enhanced by P1 dynamics are presented. First, based on the modified Lang-Kobayashi equations, a mathematical sensing model of a DOFI system working in P1 state was established. Then, simulations were carried out to verify the validity of the proposed model. After that, factors that determine the sensitivity enhancement were analyzed, based on which, theoretical analysis of achieving optimal sensitivity enhancement was performed. Next, we discussed the operation region of a DOFI system in P1 state and investigated the influence of the system parameters on the operation region. At last, experiments were conducted to verify the theoretical analyses. The results of this work provide helpful guidance for the construction of high-sensitivity DOFI sensing and measurement systems.

Комплексный подход к интеллектуализации фактического таможенного контролях в парадигме интеллектуального пункта пропуска

The article provides a justification for the application of an integrated approach for actual customs control modernization in the regions of operation of customs posts located on the Russian Federation state border. The authors analyzed the current state of equipping customs posts with technical means of customs control in accordance with the risk management system used by the Federal Customs Service of Russia, identified problematic aspects of the process of digitalization of actual customs control. Also, ways to improve the efficiency of the existing fleet of technical means and tools for the implementation of these areas are proposed.

Intraoperative angiography in neurosurgery: temporal trend, access site, and operative indication considerations from a 6-year institutional experience.

Historically, the transfemoral approach (TFA) has been the most common access site for cerebral intraoperative angiography (IOA). However, in line with trends in cardiac interventional vascular access preferences, the transradial approach (TRA) and transulnar approach (TUA) have been gaining popularity owing to favorable safety and patient satisfaction outcomes. To compare the efficacy and safety of TRA/TUA and TFA for cerebral and spinal IOA at an institutional level over a 6-year period. Between July 2016 and December 2022, 317 angiograms were included in our analysis, comprising 60 TRA, 10 TUA, 243 TFA, and 4 transpopliteal approach cases. Fluoroscopy time, contrast dose, reference air kerma, and dose-area products per target vessel catheterized were primary endpoints. Multivariate regression analyses were conducted to evaluate predictors of elevated contrast dose and radiation exposure and to assess time trends in access site selection. Contrast dose and radiation exposure metrics per vessel catheterized were not significantly different between access site groups when controlling for patient position, operative region, 3D rotational angiography use, and different operators. Access site was not a significant independent predictor of elevated radiation exposure or contrast dose. There was a significant relationship between case number and operative indication over the study period (P<0.001), with a decrease in the proportion of cases for aneurysm treatment offset by increases in total cases for the management of arteriovenous malformation, AVF, and moyamoya disease. TRA and TUA are safe and effective access site options for neurointerventional procedures that are increasingly used for IOA.