Optimal Length Research Articles

Population Dynamic of the Shield-head Catfish Synodontis Schall (Bloch & Schneider, 1801) in Upper Atbara and Setit Dam Complex, Sudan

This study aimed to assess important population bio-parameters of Synodontis schall in the Upper Atbara and the Setit dam complex (Sudan), comprising asymptotic length, growth curvature, length at maturity, optimum length, growth performance index, and mortality rate. The study was based on the need to assess capture fisheries; whose success depends on understanding the species' population structure. For five months (September 2019 and January 2020), 500 specimens of S. schall were collected randomly using gillnet from fishermen monthly. Morphometric parameters were taken in the field. The length-weight relationship demonstrated a strong correlation coefficient of r = 0.902, indicating a negative allometric growth pattern with a b-value of 2.619. The von Bertalanffy growth function was used in estimating population parameters obtained from length-frequency data; The asymptotic length (L∞) was 36.75 cm, the growth curvature (K) was 0.78 yr.-1, and the optimum length (Lopt) was 23.09 cm. The total mortality (Z) was 2.09 yr.-1; exploitation rate (E) = 0.34 yr. -1, natural mortality (M) and fishing mortality (F) = 1.39 and 0.7 yr. -1, respectively. The overall growth performance index of 3.023 indicated a slow rate of growth. The results suggest that this species and other commercial species require further research on population dynamics.

Theoretical Study of the Pre-Plasma Density Scale Length’s Influence on the Absorption Efficiency in Laser–Solid Interaction at Relativistic Laser Intensities for PW-Class Lasers

This work studied the pre-plasma that builds up in interactions of focused high-power PW-class lasers with solid targets at the target surface facing the laser beam, and its impact on the global laser absorption efficiency as well as on the spectral cut-off energy of laser-generated proton beams. Our practical heuristic estimates were derived from the example of the VEGA-3 laser at CLPU. Our modeling results for the pre-plasma expansion due to the laser pedestal of VEGA-3 were benchmarked by hydrodynamic simulations, revealing good agreement for the evolution before the arrival of the main Gaussian laser intensity peak. Our detailed numerical two-dimensional Particle-in-Cell simulations showed the impact of different pre-plasma scale lengths on the absorption efficiency of laser energy into electrons, relevant for the seeding of other types of radiation. It was shown that the absorption can increase manyfold when increasing the pre-plasma scale length. This effect can be beneficial for the spectral cut-off energy of accelerated protons, where a trade-off between absorption and electron dynamics yields an optimum pre-plasma scale length. The findings can be applied to other PW-class laser facilities.

GILLNET SELECTIVITY PARAMETERS FOR COMMERCIALLY IMPORTANT SPECIES, <i>LABEO ROHITA</i> IN A TROPICAL RESERVOIR, KERALA, INDIA

The selectivity of fishing gear characterizes its capacity and efficiency in capturing fish. This knowledge helps in selecting the appropriate mesh size to suit the available fish population. The present study aims to estimate the gillnet selectivity parameters of a commercially important fish species, Labeo rohita, from a tropical reservoir in Meenkara, Kerala, India. The study was conducted from September 2019 to February 2020 through experimental fishing using gillnets of different mesh sizes (120, 130, 140, and 150mm) of identical design and dimensions. Selectivity parameters were estimated using Holt’s indirect method. The estimated optimum selection length of L. rohita for three different mesh sizes (120, 130, and 140mm) was 46.56, 50.44, and 54.32cm, and the common selection factor (SF) was 3.88. The estimated optimum mesh size of 127 mm was found to be ideal for the commercial exploitation of L. rohita in the Meenkara reservoir. The gillnet selectivity estimates obtained in the present study will be beneficial to increase the likelihood of capturing targeted size classes as well as better management of the L. rohita fishery in Meenkara reservoir.

Does force depression resulting from shortening against series elasticity contribute to the activation dependence of optimum length?

The optimum length for force generation (L0) increases as activation is reduced, challenging classic theories of muscle contraction. Although the activation dependence of L0 is seemingly consistent with length-dependent Ca2+ sensitivity, this mechanism can't explain the apparent force dependence of L0, or the effect of series compliance on activation-related shifts in L0. We have tested a theory proposing that the activation dependence of L0 relates to force depression resulting from shortening against series elasticity. This theory predicts that significant series compliance would cause tetanic L0 to be shorter than the length corresponding to optimal filament overlap, thereby increasing the activation dependence of L0. We tested this prediction by determining L0 and maximum tetanic force (P0) with (L0_spring, P0_spring) and without added compliance in bullfrog semitendinosus muscles. The activation dependence of L0 was characterised with the addition of twitch and doublet contractions. Springs attached to muscles gave added fixed-end compliances of 11-39% and induced force depression for tetanic fixed-end contractions (P0_spring < P0). We found strong, negative correlations between spring compliance and both P0_spring (r2 = 0.89-0.91) and L0_spring (r2 = 0.60-0.63; P < 0.001), while the activation dependence of L0 was positively correlated to added compliance (r2 = 0.45, P = 0.011). However, since the compliance-mediated reduction in L0 was modest relative to the activation-related shift reported for the bullfrog plantaris muscle, additional factors must be considered. Our demonstration of force depression under novel conditions adds support to the involvement of a stress-induced inhibition of cross-bridge binding.

Erçek Gölü’nde farklı ağ göz genişliğine sahip multifilament fanyalı uzatma ağlarının seçiciliği

This study was conducted in Lake Erçek, located in the Van Lake basin. The study examined the selectivity of multifilament trammel nets used in the fishing of pearl mullet (Alburnus tarichi, Güldenstädt, 1814) in the lake. The efficiency of nets with mesh sizes of 22 mm, 24 mm, and 26 mm was evaluated in the research. A total of 5.336 pearl mullets were caught in the study carried out between October 2021 and April 2022. 1.296, 1.721 and 2.319 fish were caught from nets with mesh sizes of 22. 24 and 26 mm, respectively. The aim of the study was to determine the most suitable mesh size for sustainable pearl mullet fishing in Lake Erçek. The Holt (1963) method was used to calculate the selectivity parameters. This method considers the fish length and mesh size to determine which size of fish can be caught by the nets. The calculations showed that nets with a 26 mm mesh size had the highest efficiency and contributed to the preservation of fish stocks by allowing smaller fish to escape. The optimum catch lengths for the 22 mm, 24 mm, and 26 mm nets were calculated as 21.15 cm, 22.47 cm, and 23.69 cm, respectively. It was particularly noted that nets with a 22 mm mesh size caught fish below the legal catch size, which could negatively affect the sustainability of the fish stocks. As a result, it was concluded that nets with a 26 mm mesh size are the most suitable option for sustainable fishing in Lake Erçek. The findings of the study provide important data for the conservation of pearl mullet stocks and for the sustainable management of fishing practices.

Gillnet selectivity of commercially important fish Labeo rohita, Hamilton,1822 and Catla catla, Hamilton,1822 in kosi river, Madhepura, Bihar

Application of fishing gears in fishery is the result of experiences gained over a long period of time. Every water body has a unique pattern of fishing activity. The present study was aimed to evaluate the selectivity of gillnets and the size at first maturity of commercially important fish species in Kosi river mainly the Rohu Labeo rohita and Catla Catla catla. Experimental fishing was conducted using gillnets of different mesh sizes (60, 80, 100, 120 and 140 mm) in six sampling occasions from 2023 - 2024. A total of 2671 fish specimens consisting of 1184 L. rohita and 1523 C. catla were analyzed. Gillnet selectivity parameters for each mesh sizes were estimated for each species using the SELECT method. The size at first maturity (Lm) and its 95% CI for L. rohita and C. catla were estimated at 23.9 cm (23.3 - 24.5 cm), and 32.5 cm (31.6 - 33.4 cm), respectively. Results showed that a Log-normal model best described gillnets selectivity for C. catla, while a Normal location model best described for L. rohita. Capture probability estimates indicate that the optimum length of capture (LCAP) of &gt; 80 mm mesh size nets are smaller than the Lm of both target species, while LCAP of &gt;120 mm mesh net selects above the Lm value for both L. rohita and C. catla. Although the 100 mm mesh selects above the size of Lm value for L. rohita, it still selects below the Lm value for C. catla. Based on the results obtained, it was concluded that gillnets of mesh size 100 and 120 cm may safely be applied in Kosi river fishery if proper level of effort is applied that ensures sustainability of both target species. This study provides the baseline scenario for formulating a sustainable fisheries management strategy since many aspects of the L. rohita and C. catla fishery are not disclosed.. KEYWORDS :Rohu, Catla, optimum length of capture, SELECT model, gonad maturity, Gillnet.

Numerical Simulations of an Al2O3-Water Nanofluid-Based Linear Fresnel Solar Collector

This study aims to numerically investigate the performance of Al2O3-water nanofluid as a heat transfer fluid (HTF) in a linear Fresnel solar receiver. Although a reasonable number of studies have investigated the thermal behaviors of different nanofluids as HTF in solar collectors, the focus has so far been on the parabolic trough collectors, with little or no research efforts available for the linear Fresnel collectors. ANSYS-fluent software was utilized for the simulation in this study, which converted the governing equations to algebraic forms based on the control-volume approach. The Nusselt number and wall temperature were used to characterize the thermal performance of the nanofluid, while the friction factor and eddy viscosity were considered to determine the flow features. The correlation equation proposed by Gnielinski was used to determine the Nusselt number, while the flow features were computed using the Darcy-Weisbach equation. Additionally, the thermal performance of the nanofluid was compared directly with that of pure water. Results showed that the nanofluid improved the thermal performance by about 6-19 % across the solar receiver length. Also, the Nusselt number increases non-uniformly across the length, with a significant rise towards the trailing edge of the nanofluid flow. Conversely, the pressure drop also increases with an increase in the solar receiver length, albeit uniformly. Designers should always factor into the design process to determine the optimum solar collector length when a nanofluid is considered as the HTF; to maximize heat transfer and minimize pressure drop and its attendant economic consequences.

SPATIAL MARKET INTEGRATION AND PRICE TRANSMISSION OF COWPEA (Vigna unguiculata) IN NIGERIA

The study investigated spatial market integration and price transmission of cowpea in Nigeria. Secondary data on monthly basis for wholesale cowpea price per kilogram were used for the study. Augmented Dicky Fuller Test, Johansen Co-integration model, Granger Causality Test and Variance Decomposition of Vecto Autoregressive Model and Error Correction Model were used as analytical tools. Augmented Dickey Fuller test revealed that first difference all the price series were stationary and lag one (1) is the optimum lag length appropriate for the specified variables. Cointegration test results of the markets proved that despite that these markets were spatially separated geographically, they were connected in terms of price transmission across them, both in the long and short run but the level of integration is weak. It was observed that price changes are temporary and would converge to an equilibrium within a given time span. Granger causality test results indicate that one pair showed bi-directional causation between Bauchi and Enugu States. Thirty two (32) links showed unidirectional and three (3) pairs such as Niger→Abia, Niger→Lagos and Sokoto→Cross River States pairs showed no causal relationship between them. The study showed that Gombe and River States cowpea price had a faster speed of adjustment to equilibrium than other states. It also revealed that that 1% increase in Jigawa State will result to 20.5% increase in Enugu state and 1 % increase in River State will lead to 40.6% and 64.8% increase in Gombe and Nasarawa States in the short run respectively. The study concluded that, there is integration between the cowpea prices of source and destination states, but the degree of integration is weak. It is recommended that market participants should adopt standardize trading, settlement practice and invest in technology (electronic trading platform) to reduce operational inefficiencies in different markets to support integration.

Estimating Optimum Length of Stay in a Hospital to Control the Infection Spread during an Epidemic Using Left-Right Truncated Poisson Model

Background: The unprecedented havoc of COVID-19 pandemic stressed medical infrastructure of every affected country. The developing countries were more affected as their already inadequate medical resources were strained further. Material and Methods: In order to estimate the time of onset of recovery through the period of hospitalisation stay, the retrospective data on the number of days that 83 COVID-19 patients stayed in a hospital in New Delhi, India was obtained. A Left-Right Truncated Poisson Distribution Model (LRTPD) was developed to estimate the average number of days that patients had to spend in the hospital before the onset of recovery and they were no longer infected. Left truncation is on the ‘u’ left most classes of the random variable and right truncation is after ‘v’ classes. The parametric estimates of the LOS were validated using the Monte-Carlo method. Results and Conclusion: The models suggested that if appropriate truncation limits (both the data-specific and as per expert advice) are used in case of critical medical emergencies, approximately 90 percent of the patients will be able to get hospital admission, without over-burdening the hospital infrastructure. The median recovery onset time/ Length of stay (LOS) obtained using the Kaplan-Meier estimator was consistent with the results of the parametric modeling and simulation. However, the Kaplan-Meier method overestimated the mean LOS as compared to the parametric methods.

Estimates of life-history and growth parameters of exploited fish species in lakes Edward and George: Implications on exploitation status, population dynamics, management, and conservation of native species.

Adequate knowledge is essential for responsible inland fisheries. However, many inland fisheries lack monitoring, and therefore, decision-making for fisheries management is not reliable. In this paper, we used data from surveys and literature to estimate the life-history and growth parameters of 16 exploited fish stocks in the Ugandan part of Lake Edward and Lake George (East Africa). The estimated parameters are pivotal indicators of fish stock status, particularly in data-poor fisheries. The estimated parameters included maximum length (Lmax) and mean length (Lmean) as indicators of size structure in experimental and commercial catches, coefficients of length-weight relationships, length at 50% maturity (Lm50), fecundity, von Bertalanffy parameters, total mortality (Z), and natural mortality (M). These parameters were estimated using empirical formulae, statistical methods, and analyses of length frequencies. Only two stocks of semutundu Bagrus docmak exhibited significant and increasing trends in Lmax (Lake Edward) and Lmean (Lake George). The estimates for the remaining parameters were consistent with those in FishBase and other literature resources, either for the same species or related species. This consistency indicates their reliability for application in decision-making and further assessments. Some parameters showed evidence of unsustainable fishing. For example, estimates of Lm50 for four of the assessed stocks belonging to two species (Nile tilapia Oreochromis niloticus and marbled lungfish Protopterus aethiopicus) were lower than baseline estimates in the studied waterbodies. Furthermore, the Lmean in catches for all the stocks were less than the optimum lengths (Lopt), which maximize catches with a minimal impact on biomass and size structure. No significant changes in Lmean, length-frequency distributions, and size at maturity could be attributed to the management changes implemented in 2018, probably because it is too early to observe changes in these parameters. However, there are positive signs attributable to the changes in management as shown by a high proportion of mature individuals in commercial catches for most of the stocks for which the proportion was calculated, and an increase in Lmean and Lmax for some stocks, such as B. docmak, in commercial or experimental catches. New estimates from this study will enhance decision-making and further assessments of fisheries. Routine monitoring is recommended to update and improve the estimates.

STUDY OF THE USE OF THERMAL DRILLING IN MECHANICAL JOINING OF MG SHEET AND GFRP/CFRP COMPOSITES WITH THERMOSOFTENING MATRIX

The paper discusses the joining of magnesium based metallic sheet and composites with thermosoftening polypropylene matrix reinforced with bi-directional continuous glass and carbon fibers by thermal drilling technology. The bushing formation has been investigated by separately drilling AZ91 Mg alloy sheet at two rotational speeds and feed rates to find out the parameters at which a bushing with optimum length and thickness, suitable for joining with the composite, is formed. Under these conditions, the joining of the metal sheet and composite was then carried out by simple thermal drilling. During simple drilling, delamination of the composite occurred in the vicinity of the hole, which was resolved by flanging the bushing with a penetration of the tool from the opposite side. When AZ91 was joined to carbon fibers reinfirced composite, there was a lack of bushing formation due to the higher resistance of the carbon fibers, which are present in the composite in greater numbers compared to the glass fibers. This problem was solved by sequential drilling, which means that a flowdrill tool was used to create a hole in the composite itself, then overlaid with Mg sheet and again drilled, forming the bushing and flanging the bushing from the opposite side. The sequential drilling resulted in joints with a load capacity of 0.8 - 1.4 kN, which exhibit the characteristics of a hybrid - mechanical and adhesive joint.

Grouping Library Book Collection Based On Old Book Borrowers With Clustering Method (Case study: STMIK Kaputama)

Libraries are institutions that collect printed and recorded knowledge. Books can be borrowed at the library for a length of time according to library regulations. Based on observations that some types of books in the library of STMIK Kaputama have a very high ratio of the number of borrowers, while the availability of books is limited. The addition of new book collections cannot be done because the storage capacity of the collection is limited. Based on these conditions, the grouping of book collections based on the length of book borrowing is carried out to optimize the service time for borrowing books. This application was created to assist librarians in determining the optimal length of book borrowing. So in this case, we will design and build a system that will be used in grouping library book collections based on the length of borrowing and the variables determined using the clustering method. The purpose of this research is to design and build a system for grouping library book collections in order to produce information quickly about the availability of books in the library.

Is the population of kingfish (Scomberomorus commerson) in the northern Persian Gulf really under pressure from overfishing?

AbstractQuantifying the population dynamics of marine species is difficult when good, comprehensive data are not available. We sought to determine if the kingfish Scomberomorus commerson stock in the Persian Gulf was overfished. The ICES data‐limited assessment framework was used to provide precautionary advice, with a 20% decrease advised in situations where only catch or bycatch data were available. The length‐based Bayesian biomass (LBB) was used to model fork length from landing records of licensed fishers in the Khuzestan Province during 2002–2018, which had increased despite sought being overexploited. Most kingfish were immature and smaller than optimum length of the catch (Lc‐opt = 88 cm) and optimum length (Lopt = 104 cm). Relative biomass (B/Bmsy) ranged 0.62–0.66 and exceeded 0.5. The B/Bmsy ratio (1.25) was &gt;1.1. The stock appeared to be healthy and exploitable, but wide confidence intervals of the B/Bmsy ratio complicated interpretation of stock status. The kingfish stock appeared to use waters of the study area as a spawning and nursery ground, so many young immature individuals were present. If current exploitation of young individuals continues, this the stock will eventually be overfished. Long‐term increases in the catch of young immature kingfish can have a side effect on stock maturation and recruitment. We recommend that the mesh size of fishing gear be selected based on optimum length, to enhance economic, and commercial viability of the kingfish fishery.

Understanding the limitations of grain yield monitor technology to inform on‐farm research

AbstractYield monitoring technology (YM) is a valuable tool to evaluate crop performance in on‐farm research (OFR). However, limited information exists on utilizing this technology to accurately inform OFR. The objectives of this study were to evaluate the ability of grain yield monitor mass flow sensors to detect changes in corn (Zea mays L.) yield for different plot lengths, provide a recommended minimum plot length to utilize YM in OFR, and determine if differences in estimating yield existed between YMs. Six treatment lengths that varied in distance of intentional yield differences (7.6, 15.2, 30.5, 61.0, 121.9, and 243.8 m) were created by alternating high‐yield (202 kg N/ha application) and low‐yield (0 kg N/ha application) plots. A total of four grain YMs with impact‐style mass flow sensors were used within two commercially available combines. Yield comparisons were made between the plot combine and YMs to evaluate the accuracy of each technology for detecting the magnitude of yield change across lengths using analysis of variance and exponential regression curves. Results indicated that the mass flow sensors were not sensitive enough to detect quickly changing flow rates for alternating yield changes in small plot lengths. Minimum plot lengths ranged from 43 to 107 m depending on YM. Significant differences were observed between grain YMs from different manufacturers. Future work could evaluate the influence additional crops or smaller yield differences have on the optimum OFR plot length.

Flexural behavior of concrete reinforced with micro basalt fibers and BFRP minibars

The use of basalt fibers as the reinforcement for concrete is an effective and eco-friendly solution to improve the ductile behavior and flexural toughness. For this purpose, an experimental investigation was conducted, where the concrete reinforced with micro basalt fibers or BFRP minibars were adopted. The morphologies of micro basalt fibers, straight, twisted and crimped BFRP minibars were analyzed for optimal enhancement effect. Also, the fiber length of 20 mm, 35 mm and 50 mm and fiber volume fraction of 0.5 %, 1 %, 2 % and 3 % were investigated. In addition, stiffer steel and softer polypropylene fibers were introduced to evaluate the effect of fiber modulus on concrete properties. The failure modes, load-deflection curves, fracture energy, flexural toughness and factor analysis were illustrated. The results show that the addition of micro basalt fibers with fiber lengths of 50 mm and volume fraction of 1 % increased the initial cracking strength by 28.8 %. Concrete reinforced with BFRP minibars with 50 mm in length and 1 % in volume fraction, has a flexural toughness ratio of 99.0 % of commercial steel fibers and a flexural toughness index (I5) of 113 % of commercial steel fibers. Based on the parametric analysis, the optimum length of BFRP minibars was 35 mm and the optimum fiber volume fraction was not more than 2 %. The prediction model for stress deflection response with high precision was proposed with regression coefficients ranging from 0.909 to 0.988. It was concluded that micro basalt fibers prevented the generation of microcracks through the bridging effect, whereas macrocracks and deep source cracks generated after concrete cracking were inhibited by BFRP minibars. The understanding of what exactly constitutes an optimal selection of fibers capable of producing maximum flexural properties of concrete was of great significance in engineering applications.

Numerical Analysis of the Discrete, Fractional Order PID Controller Using FOBD Approximation

This paper proposes a methodology of the numerical testing of the discrete, approximated Fractional Order PID Controller (FOPID). The fractional parts of the controller are approximated using the Fractional Order Backward Difference (FOBD) operator. The goal of the analysis is to find the memory length optimum from point of view both accuracy and duration of computations. To do it new cost functions describing both accuracy and numerical complexity were proposed and applied. Results of tests indicate that the optimum memory length lies between 200 and 400. The proposed approach can be also useful to examine of another discrete implementations of a fractional order operator using FOBD.

Kinematic bearing capacity analysis of strip footings on reinforced soils using discretisation technique

The kinematic discretisation technique of upper bound limit analysis is adopted in this study to evaluate the limit load of a strip footing located on the soils reinforced with different geosynthetic layers. The reinforcement is assumed to withstand the tension but not bending moment. The failure model of the reinforced foundation soil is generated using the discretisation method, a ‘point by point’ technique. Two failure modes of the reinforcement, the tensile rupture and sliding, are considered in the analysis. This article proposed the formulas for the first time to evaluate the effect of soil friction angle φ on the ultimate bearing capacity and on the failure mechanism of foundation. The calculation results are given considering different reinforcement layers, which describe the impact of different reinforcement depth and length on the ultimate bearing capacity. The optimum positions of different reinforcement layers and the optimum reinforcement length are obtained. The bearing capacity ratios are also presented in figures combing impact of reinforcement depths, soil cohesion and friction angle. The present method was verified by the results reported in literature. The present method can provide a reference for the footing design on the reinforced soils.

Energy efficiency and greenhouse gas emissions: A panel ARDL model of top five emitters in Africa

The Paris Agreement has mandated drastic decarbonization by developed and developing economies. Many of the top African emitters are now exploring drastic restructuring of the production processes in a way that promotes energy utilization efficiency. This is critical for ensuring an environmentally benign growth process. This study presents a unique addition to the body of existing knowledge by analysing the effect of some indicators of energy efficiency on three indicators of environmental quality among the top five emitters of GHG in Africa. The data were from the World Development Indicators (WDI), covering the 1990–2020 periods for South Africa, Egypt, Nigeria, Algeria, and Libya. The panel Autoregressive Distributed Lag (ARDL) model was used for data analysis. The results showed that all the included series were stationary at first difference. The optimum lag lengths were determined independently in STATA 17 software, and the most frequent lags across the countries were selected. The Hausman test revealed that the pooled mean group (PMG) estimation was preferred to other estimators. The results showed that in the long-run, particulate emission damages, CO2 intensity, and energy use intensity positively impacted GHG emissions, while GDP per capita and renewable energy utilization produced mixed results. In the short run, the error correction mechanism parameters were all significant (p < 0.01) in Libya for all emission indicators, while Algeria showed significance (p < 0.01) in total GHG and CO2 per capita models. The coefficient of particulate emission damages significantly reduced (p < 0.01) total GHG emissions in Libya and Nigeria and renewable energy significantly increased (p < 0.01) GHG emissions in South Africa but reduced them in Nigeria. Also, CO2 emission intensity significantly (p < 0.01) and positively impacted GHG emissions in South Africa, Egypt, Libya, and Nigeria, while electricity power transmission losses increased total emissions and CO2 emissions in Libya and Algeria. It was concluded that initiatives to reduce GHG emissions should focus on developing countries’ sensitivity to emission damages, and promotion of initiatives for using renewable energies. Also, promotion of energy efficiency across industries offers a prospect for ensuring environmental sustainability.

PSIX-28 Optimization of feeding trial length for evaluating feed efficiency in sheep

Abstract Feed efficiency tests are well established for beef cattle, but testing for sheep remains rare due to the lack of appropriate equipment and standardized protocols. To explore the optimum trial length for evaluating feed efficiency in sheep, freshly weaned Rideau Arcott ewe lambs [n = 80; 4to 5 mo of age and body weights (BW) of 16 to 25 kg] were enrolled in a 65-d feeding trial, following a 20-d adaptation period. A mixed ration containing barley gain and protein supplement pellets were offered twice daily, and lambs had ad libitum access to feed, water and bedding straw during the trial period. Daily feed intake of individual lambs was monitored with Vytelle SENSE feed bunks, BW was recorded biweekly, as well as on two consecutive days at the start and end of the trial. Lambs that had died or had abnormal growth patterns from sickness were removed, resulting in 62 lambs remaining in the final dataset. Optimum trial length for measuring feed intake (DMI) and average daily gain (ADG) were evaluated with R Software (v. 4.3.3) via a post-hoc analysis of constructing shortened trial lengths from the regular test. The DMI and ADG values from the shortened trial datasets were compared with those from regular trial days with correlation (Pearson and Spearman tests) and linear regression analyses. There were 64 shortened trial lengths for DMI by 1 d increments, and 15 sub-datasets for ADG consisting of trial lengths between every two BW measurements. Residual feed intake (RFI), residual average daily gain (RADG), and residual intake and BW gain (RIG) were calculated for and compared between the regular trial length (65 d) and favorable shortened trial lengths based on DMI and ADG evaluations. Correlation, regression and agreement analyses were used to determine the optimum trial lengths for RFI, RADG and RIG evaluations. Results showed that DMI and ADG measurements could be shortened to 42 (r &amp;gt; 0.95, R2 &amp;gt; 0.90, β &amp;gt; 0.95, P &amp;lt; 0.001) and 56 d (r &amp;gt; 0.96, R2 &amp;gt; 0.93, β &amp;gt; 0.96, P &amp;lt; 0.001), respectively. Additionally, trial length for RFI, RADG, and RG evaluations could be reduced to 56 d (r &amp;gt; 0.95, R2 &amp;gt; 0.91, β &amp;gt; 0.95, CCC &amp;gt; 0.95, P &amp;lt; 0.001), primarily due to the trial length requirement for accurate ADG measurement. Reducing the duration of trials for evaluating feed efficiency in sheep not only reduces testing costs, fostering greater uptake among sheep producers, but also allows for the evaluation of more lambs annually, thereby enhancing the overall productivity and profitability of the sheep industry.

Experimental optimization and evaluation of an R600a/R1150 auto-cascade refrigeration systems for ultra-low temperature applications

Auto-cascade refrigeration systems are the most employed systems for ultra-low temperature applications, especially for small capacity systems. Recent investigations have allowed to analyze them energetically and thermodynamically, starting a research line focused on enhancing their energy performance from experimental approaches. This work focuses on the energy optimization of a real auto-cascade system working with the mixture R600a/R1150 [70/30 %], which has been evaluated using two compressor models for R404A and R290 as well as the optimization of the two capillary tubes used in the system. Results indicate that overall efficiency of the R290 compressor is up to 21 % higher than with R404A, leading to COP increments between 35 and 81 %. Optimum capillary lengths have been determined in terms of COP and energy consumption, reaching similar values, however, the inner parameters of the system change as function of these lengths, which needs to be considered in prototypes design.