Matching with floor constraints

Floor constraints are a prominent feature of many matching markets, such as medical residency, teacher assignment, and military cadet matching. We develop a theory of matching markets under floor constraints. We introduce a stability notion, which we call floor respecting stability, for markets in which (hard) floor constraints must be respected. A matching is floor respecting stable if there is no coalition of doctors and hospitals that can propose an alternative matching that is feasible and an improvement for its members. Our stability notion imposes the additional condition that a coalition cannot reassign a doctor outside the coalition to another hospital (although she can be fired). This condition is necessary to guarantee the existence of stable matchings. We provide a mechanism that is strategy‐proof for doctors and implements a floor respecting stable matching.

A Comparative CFD Study of Two Air Distribution Systems with Hot Aisle Containment in High-Density Data Centers

Removing heat from high-density information technology (IT) equipment is essential for data centers. Maintaining the proper operating environment for IT equipment can be expensive. Rising energy cost and energy consumption has prompted data centers to consider hot aisle and cold aisle containment strategies, which can improve the energy efficiency and maintain the recommended level of inlet air temperature to IT equipment. It can also resolve hot spots in traditional uncontained data centers to some degree. This study analyzes the IT environment of the hot aisle containment (HAC) system, which has been considered an essential solution for high-density data centers. The thermal performance was analyzed for an IT server room with HAC in a reference data center. Computational fluid dynamics analysis was conducted to compare the operating performances of the cooling air distribution systems applied to the raised and hard floors and to examine the difference in the IT environment between the server rooms. Regarding operating conditions, the thermal performances in a state wherein the cooling system operated normally and another wherein one unit had failed were compared. The thermal performance of each alternative was evaluated by comparing the temperature distribution, airflow distribution, inlet air temperatures of the server racks, and recirculation ratio from the outlet to the inlet. In conclusion, the HAC system with a raised floor has higher cooling efficiency than that with a hard floor. The HAC with a raised floor over a hard floor can improve the air distribution efficiency by 28%. This corresponds to 40% reduction in the recirculation ratio for more than 20% of the normal cooling conditions. The main contribution of this paper is that it realistically implements the effectiveness of the existing theoretical comparison of the HAC system by developing an accurate numerical model of a data center with a high-density fifth-generation (5G) environment and applying the operating conditions.

Accuracy and spread of nest search behaviour in the Saharan silver ant, Cataglyphis bombycina, and in the salt pan species, Cataglyphis fortis

Desert ants of the genus Cataglyphis are renowned for their navigation abilities, especially for their beeline homing after meandering foraging excursions reaching several hundreds of meters in length. A spiralling nest search is performed when an ant misses the nest entrance upon completing its homebound travel. We examined the nest search behaviours of two desert ant species dwelling in different habitats—Cataglyphis bombycina living in the dunes of the Sahara and Cataglyphis fortis found in the salt pans of North Africa. The two species show distinct differences in walking behaviour. C. bombycina performs a strict tripod gait with pronounced aerial phases, high stride frequencies, and extremely brief ground contact times. In view of these peculiarities and the yielding sand dune substrate, we hypothesised that homing accuracy, and namely distance measurement by stride integration, should be lower in C. bombycina, compared to the well-studied C. fortis with less specialised walking behaviour. We tested this hypothesis in ants’ homebound runs from a feeding site in a linear channel setup. Surprisingly, the accuracies of nest searches were similar in the two ant species, and search accuracy was also independent of the walking substrate, soft dune sand or a hard floor. The spread of the nest search, by contrast, differed significantly between the two species, C. bombycina exhibiting a larger search spread. This may be interpreted as an increased path integration uncertainty due to the above locomotor specialisations, or as a compensation strategy accounting for the silver ants’ particular environmental and behavioural situation.

Influence of Flooring on Lower Extremity Blood Oxygenation and Volume during Prolonged Standing

Prolonged standing is an occupational hazard that may evoke many cardiovascular problems. This study investigates the effects of anti-fatigue mats on hemoglobin levels—related to blood pooling—in the lower extremities during prolonged standing. Fifteen subjects (6 M, 9 F; Age = 26 ± 3 years; BMI = 23.2 ± 2.5 kg/m2) stood for one hour on a hard floor and anti-fatigue mat. Oxygenated (HbO), deoxygenated (HbR), and total (HbT) hemoglobin levels were measured for the soleus muscle using near infrared spectroscopy. A mixed-effects model was performed indicating that time, flooring, and their interaction effect were significantly associated with levels of HbO (time, p<0.0001; floor, p=0.0056; interaction, p=0.0033), HbR (time, p<0.0001), and HbT (time, p<0.0001; floor, p=0.0060; interaction, p=0.0062). Results indicate that hemoglobin levels change with time, and flooring has an effect. Blood pooling seems to be the mechanism. Anti-fatigue mats may have a positive effect on cardiovascular outcomes.

The influence of conditions of detention the hoof and the development of aseptic inflammation of the producing layer of the base of the skin soles hooves in the cows

Violation of the conditions of animals keeping and the lack of proper level of veterinary and sanitary culture on farms does not allow to achieve a balance between the organism of the cattle and the environment of its stay. The uneven distribution of body weight on the surface of the sole caused by keeping animals on a rough floor promotes the emergence of producing corns, stretching of the tendons and ligaments, slippery flooring leads to the fall of animals and the occurrence of various injuries, in particular, fractures of the limbs, tensile bond, capsule of the joint, excessively hard floor – to excessive erosion of the horn of the sole, etc. In such herds it is difficult to maintain animal health at the proper level and prevent the occurrence of, in particular, aseptic pododermatitis. The article deals with the results on the dissemination of aseptic pododermatitis in cows for the presence of animals on wooden and reinforced concrete slit floors during the winter and standstill period of containment. It has been established that aseptic pododermatitis in cows on reinforced concrete slit floor is registered in 71.6% of cases, while on wooden – only 28.4%. In the hoof horn of the thoracic and pelvic extremities of the cows, with aseptic pododermatitis, the amount of moisture decreased by 8.2 and 9.3% respectively, the concentration of SH-groups increases by 10.6 and 15.8%, with a possible decrease in the content of calcium, sulfur, cuprum and zinc; decreases the hoof horn density and resistance to abrasion of the epithelium of the hooves of the pelvic limbs by 1.6 and 18.0%, as well as the intensity of the abrasion sole hooves of the thoracic and pelvic limbs is increased by 7.5 and 20.0%, which helps to reduce the growth of the epidermis of the sole. Consequently, changes in certain biochemical and biophysical indices of hoof horns of cows suffering from aseptic pododermatitis, which were held on the reinforced concrete slit, indicate a deterioration in the quality of the epidermal hooves and excessive erosion of the sole, which is one of the causes of the occurrence and development of aseptic pododermatitis in cows.

Comparing Performance Metrics of Partial Aisle Containments in Hard Floor and Raised Floor Data Centers Using CFD

In data centers, efficient cooling systems are required to both keep the energy consumption as low as possible and to fulfill the temperature requirements. The aim of this work is to numerically investigate the effects of using partial aisle containment between the server racks for hard and raised floor configurations. The computational fluid dynamics (CFD) software ANSYS CFX was used together with the Reynolds stress turbulence model to perform the simulations. Velocity measurements in a server room were used for validation. Boundary conditions and the load of each rack were also retrieved from the experimental facility, implying an uneven load between the racks. A combination of the performance metrics Rack Cooling Index (RCI), Return Temperature Index (RTI) and Capture Index (CI) were used to evaluate the performance of the cooling systems for two supply flow rates at a 100% and 50% of operating condition. Based on the combination of performance metrics, the airflow management was improved in the raised floor configurations. With the supply flow rate set to operating conditions, the RCI was 100% for both raised floor and hard floor setups. The top- or side-cover fully prevented recirculation for the raised floor configuration, while it reduced the recirculation for the hard floor configuration. However, the RTI was low, close to 40% in the hard floor case, indicating poor energy efficiency. With the supply flow rate decreasing with 50%, the RTI increased to above 80%. Recirculation of hot air was indicated for all the containments when the supply rate was 50%, but the values of RCI still indicated an acceptable performance of the cooling system.

Effect of Flooring on Lower Extremity Discomfort during Food Service Tray-line Jobs

This paper investigate the extent to which flooring mats affect stress and fatigue among food service workers on trayline duties. A food service trayline job was simulated in the lab to study the effect of the flooring mat on the lower leg swelling, muscle temperature, fatigue levels and discomfort levels. Six participants participated in the study and performed a 1-hour simulated trayline job. Results showed a significant effect of flooring condition on the muscle temperature change in Tibialis Anterior and Quadriceps with decreasing trend observed for hard floor condition. Results also indicated an increasing trend for leg volume and higher fatigue and discomfort in hard floor condition.

Long-Lasting Changes in Muscle Twitch Force During Simulated Work While Standing or Walking

Objective: The aim of this study was to evaluate the long-lasting effects of prolonged standing work on a hard floor or floor mat and slow-pace walking on muscle twitch force (MTF) elicited by electrical stimulation. Background: Prolonged standing work may alter lower-leg muscle function, which can be quantified by changes in the MTF amplitude and duration related to muscle fatigue. Ergonomic interventions have been proposed to mitigate fatigue and discomfort; however, their influences remain controversial. Method: Ten men and eight women simulated standing work in 320-min experiments with three conditions: standing on a hard floor or an antifatigue mat and walking on a treadmill, each including three seated rest breaks. MTF in the gastrocnemius-soleus muscles was evaluated through changes in signal amplitude and duration. Results: The significant decrease of MTF amplitude and an increase of duration after standing work on a hard floor and on a mat persisted beyond 1 hr postwork. During walking, significant MTF metrics changes appeared 30 min postwork. MTF amplitude decrease was not significant after the first 110 min in any of the conditions; however, MTF duration was significantly higher than baseline in the standing conditions. Conclusion: Similar long-lasting weakening of MTF was induced by standing on a hard floor and on an antifatigue mat. However, walking partially attenuated this phenomenon. Application: Mostly static standing is likely to contribute to alterations of MTF in lower-leg muscles and potentially to musculoskeletal disorders regardless of the flooring characteristics. Occupational activities including slow-pace walking may reduce such deterioration in muscle function.