Leg Length Ratio Research Articles

Optimization analysis for thermoelectric performance improvement of biconical segmented annular thermoelectric generator

Thermoelectric generators have struggled with low efficiency, limiting their widespread use. To further improve the performance of the thermoelectric generator, this paper introduces the biconical pin structure into the segmented annular thermoelectric generator, and simultaneously incorporates exergy efficiency and economic cost to evaluate its performance. Experiments are first used to verify the accuracy of the simulation model, and then the effects of the cone angle θ, leg height H, leg length ratio δ and resistance ratio ε are discussed. Finally, correlation analysis is used to obtain the weight of the impact of research parameters on thermoelectric performance, and the optimized results are obtained. The results demonstrate that the output power of the biconical segmented annular thermoelectric generator is 20.23 % higher, the exergy efficiency is 8.55 % higher, and the economic cost is reduced by 21.36 % compared to the traditional segmented annular thermoelectric generator. As the θ and H increase, the thermoelectric performance enhances. The influence of δ on thermoelectric performance is more complicated. When ε is 1.5, the thermoelectric generator has optimal thermoelectric performance. This paper provides a reference for optimizing the segmented annular thermoelectric generator structure and is of paramount importance for enhancing the efficiency of waste heat recovery.

Humero-femoral index and diabetes risk in the US population- a case study.

The between-subject variability in diabetes risk persists in epidemiological studies, even after accounting for obesity. We investigated whether the humero-femoral index (HFI) was associated with prevalence of type 2 diabetes mellitus (T2DM) and assessed the incremental value of HFI as a marker of T2DM. This population-based cross-sectional study used data from the National Health and Nutrition Examination Survey from 1999 to 2018. We assessed 42,088 adults aged ≥ 30 years. HFI was defined as the upper arm length/upper leg length ratio. The outcome included undiagnosed diabetes (based on 2-hour plasma glucose levels, fasting glucose and hemoglobin A1C) and history of diabetes (diagnosed diabetes or taking antidiabetic drugs). As compared with the bottom quartile, the prevalence ratio of T2DM was 1.28 (95% CI 1.19-1.38) in the second, 1.61 (95% CI 1.50-1.72) in the third, and 1.75 (95% CI 1.64-1.88) in the fourth quartile of HFI (P for trend < 0.0001). The positive association remained consistent within different patterns of BMI and WC in men but was rendered null in women. After adding HFI to the reference model (including WC only), the discrimination slopes increased by 60.0% in men and 51.1% in women. Our findings suggest that HFI may be a key component in body structure contributing to the risk of T2DM. In men, the highest HFI was associated with elevated prevalence of T2DM, independent of BMI and WC. The online version contains supplementary material available at 10.1007/s40200-023-01251-z.

Equivalent running leg lengths require prosthetic legs to be longer than biological legs during standing

We aimed to determine a method for prescribing a standing prosthetic leg length (ProsL) that results in an equivalent running biological leg length (BioL) for athletes with unilateral (UTTA) and bilateral transtibial amputations (BTTA). We measured standing leg length of ten non-amputee (NA) athletes, ten athletes with UTTA, and five athletes with BTTA. All athletes performed treadmill running trials from 3 m/s to their maximum speed. We calculated standing and running BioL and ProsL lengths and assessed the running-to-standing leg length ratio (Lratio) at three instances during ground contact: touchdown, mid-stance, and take-off. Athletes with UTTA had 2.4 cm longer standing ProsL than BioL length (p = 0.030), but their ProsL length were up to 3.3 cm shorter at touchdown and 4.1 cm shorter at mid-stance than BioL, at 3–11.5 m/s. At touchdown, mid-stance, and take-off, athletes with BTTA had 0.01–0.05 lower Lratio at 3 m/s (p < 0.001) and 0.03–0.07 lower Lratio at 10 m/s (p < 0.001) in their ProsL compared to the BioL of NA athletes. During running, ProsL were consistently shorter than BioL. To achieve equivalent running leg lengths at touchdown and take-off, athletes with UTTA should set their running-specific prosthesis height so that their standing ProsL length is 2.8–4.5% longer than their BioL length, and athletes with BTTA should set their running-specific prosthesis height so that their standing ProsL lengths are at least 2.1–3.9% longer than their presumed BioL length. Setting ProsL length to match presumed biological dimensions during standing results in shorter legs during running.

The Effect of Small Box Plyometric and Alternate Leg Bound Training Methods on Long Jump in Students in Class XI State Madrasa Aliyah 5 of Jombang

This research is irritated by the observation that athletic achievement cannot be achieved speculatively, but must go through intensive training with the right training program. These determinants and supporting factors for achievement can be used as a basis for preparing a training program. One of the supporting factors in increasing long jump results is physical exercise. Several methods of physical training can be put forward such as weight training, interval training, circuit training, and small box plyometric exercises. In accordance with the formulation of the problem, the purpose of this study was to determine the difference in the effect of the small box plyometric and Alternate Leg Bound training methods on long jump results in class XI students at State Madrasa Aliyah 5 Jombang. large, medium, and small bodies in class XI students at State Madrasa Aliyah 5 Jombang and to determine the effect of the interaction between the small box plyometric training method and alternate leg bound and the ratio of leg length and height to the results of the long jump in class XI students at State Madrasa Aliyah 5 Jombang. Based on the results of field research, the two plyometric training methods have different results in the long jump. This is evidenced by the value of Fcount = 6.299 &gt; Ftable = 4.04 at a significant level = 0.05 with a p-value = 0.016 &lt;0.05, the difference in the increase in long jump results between students who have large, medium and small leg length and height ratios. This is evidenced by the value of Fcount = 27.786 &gt; Ftable = 3.17 at a significant level = 0.05 with a p-value = 0.000 &lt;0.05 and the interaction between plyometric training methods and the ratio of leg length to height is very significant. This is evidenced by the value of Fcount = 24.542 &gt; Ftable = 3.16 at a significant level = 0.05 and p-value = 0.000 &lt;0.05. Based on the conclusions in this study, it turns out that the application of the right training method will have a significant influence on the results of learning or training. The small box plyometric and alternate leg bound training methods and the ratio of leg length to body height is the variables that influence the long jump results. Keywords: [Training Method, Long Jump, Athletics]

Association of early menarche with elevated BMI, lower body height and relative leg length among 14- to 16-year-old post-menarcheal girls from a Maya community in Yucatan, Mexico

Human body segments have different timing and tempo of growth. Early menarche (EM) as an indicator of early reproductive maturity results in a shortened height and leg length. Relatively larger trunk may increase risk for more body fat deposit and higher body mass index (BMI) due to the allometry of total body fat with body proportions. The objective of the study was to assess the association of EM with BMI, absolute body size [height, sitting height (SH), subischial leg length (SLL)] and relative body dimensions [sitting height to subischial leg length ratio (SHSLLR), relative subischial leg length (RSLL)] among 14- to 16-year-old post-menarcheal girls from a rural Maya community in Quintana Roo, Yucatan, Mexico. In a cross-sectional study, post-menarcheal girls (n=51) aged 14 to 16 years had EM (n=22) (&lt;12 years of age) and not early menarche (NEM, n=29). Anthropometric measurements of height, weight, and SH were recorded. Derived variables were BMI, height and BMI-for-age z-scores, SLL, SHSLLR, and RSLL. Mean value of age at menarche (AM) was 13 years (EM 11 years, NEM 14 years). Mean values of height (EM 159 cm, NEM 164 cm), BMI (EM 20 kg/m2, NEM 19 kg/m2), sitting height (EM 81 cm, NEM 78 cm), SLL (EM 79 cm, NEM 85 cm), SHSLLR (EM 102.93%, NEM 92.03%), and RSLL (EM 49%, NEM 52%) were different (p&lt;0.05) in the two groups. BMI showed significant negative correlation with AM (Pearson’s r=-0.29, p&lt;0.04). Linear regression models adjusted for age showed that EM had different interrelationships (p&lt;0.05) with body dimensions: positive with BMI, SH, SHSLLR, and negative with height, SLL, and RSLL. Earlier AM was associated with higher BMI, SH, SHSLLR and lower SLL, RSLL, explaining lower body height and leg length among the participant EM girls. In the light of life history theory, EM results in a growth trade-off, short stature and larger trunk relative to leg length that might enhance risk for body fat gain.

Model for Prediction of the Weight and Height Measurements of Patients with Disabilities for Diagnosis and Therapy

Background: Accurate measurement of a patient’s height and weight is an essential part of diagnosis and therapy, but there is some controversy as to how to calculate the height and weight of patients with disabilities. Objective: This study aims to use anthropometric measurements (arm span, length of leg, chest circumference, and waist circumference) to find a model (alternatives) that can allow the calculation of the height and the body weight of patients with disabilities. Additionally, a model for the prediction of weight and height measurements of patients with disabilities was established. Method: Four hander patients aged 20-80 years were enrolled in this study and divided into two groups, 210 (52.5%) male and 190 (47.5%) female. Result: A significant correlation was noted between body height and arm span, as well as between body height and length of leg in all study groups. The body weight and the ratio of arm span or leg length to the sum of chest and waist circumferences were found to have a negative significant correlation. Model equations were derived to estimate the height and body weight according to anthropometric measurements. Conclusion: Anthropometric measurements can be used to create a model for calculating the body height and body weight of patients with disabilities and which can be considered an alternative to measurements that can be made on otherwise healthy subjects.

Relationships between physical characteristics and biomechanics of lower extremity during the squat

Background/objectiveThere is a lack of information about relationship between physical characteristics and biomechanics of the lower extremity during the squat. Additionally, studies did not examine sex-related differences. The purpose of this study was to investigate relationships between physical characteristics and biomechanics of the lower extremity during the squat, and to determine if any sex differences are present. MethodsFifty three participants recruited (21.82 ± 2.3 years; 75.56 ± 14.98 kg; 171.57 ± 8.38 cm) performed three squats with 75% of one repetition maximum. Femur to tibia length ratio, hip and ankle joints’ flexibilities, and relative muscular strength were measured and used as physical characteristics. Net joint torques (NJT) and flexion angles of the lower extremity were extracted as dependent variables. Multiple regression (stepwise) analysis was conducted to examine the relationships with physical characteristics being factors. Pearson correlation coefficients were calculated to determine intercorrelations among the dependent variables. ResultsRelative muscular strength was related to hip NJT and knee flexion angle, and hip flexibility was related to ankle dorsiflexion. Hip and knee NJT showed moderate correlations with the corresponding flexion angles (r = 0.48-0.53; p < .01). Ankle dorsiflexion angle showed weak to moderate correlations with hip NJT and hip flexion angle (r = −0.36-0.50; p < .01) and a moderate correlation with knee NJT. No significant sex difference was observed (r = 0.52; p < .05). ConclusionBiomechanics of the lower extremity has been shown to correlate more with relative muscular strength and joint flexibility than with leg length ratio.

Analytical model-based optimization of the thermoelectric cooler with temperature-dependent materials under different operating conditions

This paper presents a novel general single/multi-parameter optimization model for the thermoelectric cooler (TEC) based on the 1D resistance method, which precisely captures all the thermoelectrical effects and the impacts of temperature-dependent thermoelectric properties, thermal operating conditions, and contact resistance at the solder layer, respectively. The explicit analytical expressions of designed optimal parameters, including the applied current, thermoelectric leg length, the cross-section area ratio of P/N-type thermoelectrical legs, and the number of leg pairs, are derived to maximize TEC performances (such as cooling capacity, coefficient of performance, or temperature difference between the cold/hot sides) under different operating conditions. The validation of the developed model is conducted through comparisons with the reported experimental data or 3D simulation results. The inherent correlations between the designed parameters are demonstrated and used to clarify the conflicting results in the literature. The ratio of leg length and its area cannot be assumed as an independent optimal parameter for large contact resistance. The filling ratio of thermoelectrical legs should be chosen as large as possible and limited by the manufacturing technology. It is demonstrated that the multiplication of applied current and number of leg pairs could be considered an independent optimal parameter, which provides a new strategy to design the available applied current for practical applications. The correlation between applied current and leg length is also discussed in detail. Multi-parameter optimization could remarkably improve the TEC performance compared with the single-parameter model, such as a significant improvement by 31% for the optimal cooling capacity. The cooling capacity is enhanced by 98% when the convective heat transfer coefficient of 1000 W/m2K at the cold/hot sides increases to 2000 W/m2K. A decrease of 15% for cooling capacity induced by the contact resistance is also observed. The present work provides a promising comprehensive tool for intensifying TEC performance maximization and clarifying its impact factors and the multi-parameter inherent correlation.

Numerical Study on Optimizing the Geometry of Segmented Asymmetrical Thermoelectric Generator

Quite large amount of heat generated in various industrial processes was wasted. Recovering the waste heat can save cost and benefit the environment protection. The device that convert heat energy to electricity is called thermoelectric generator (TEG), and therefore it can be used for waste heat recovery. Improving the efficiency is the main direction of present study. The configuration and geometry of the thermoelectric legs are proved can influence the thermoelectric performance of the thermoelectric generator. Compared with the conventional TEG which is assembled with symmetrical (rectangular) legs, asymmetrical thermoelectric generator (ATEG) has a greater temperature gradient in a leg due to the convergent geometry which can reduce overall thermal conduction of the device and Thomson effect is also harnessed. In this study, three-dimensional finite element analysis (COMSOL) is employed to investigate the numerical simulations of a segmented pyramidal thermoelectric generator (SPTEG) and a segmented cone thermoelectric generator (SCTEG) to optimize the leg length ratio of two materials, and it’s effect on the electrical and mechanical performances of SPTEG and SCTEG was also studied. Results obtained shows that the height ratio of SATEG can influence electrical and mechanical performances and the optimum height ratio provided a better electrical performance while thermal stress developed in leg was less. In addition, the open-circuit voltage of two types SATEG is similar because they have the same cross sectional area and the same volume, however, SCTEG has a dispersive thermal stress distribution while the thermal stress of SPTEG concentrates in four corners. Compared to the maximum von Mises stress in SPTEG, the maximum von Mises stress in SCTEG reduced about 10%. Results obtained from this study would provide references in producing and design of segmented asymmetrical thermoelectric generators.

A Center of Mass Estimation and Control Strategy for Body-Weight-Support Treadmill Training.

Walking disorders are common in post-stroke. Body weight support (BWS) systems have been proposed and proven to enhance gait training systems for recovering in individuals with hemiplegia. However, the fixed weight support and walking speed increase the risk of falling and decrease the active participation of the subjects. This paper proposes a strategy to enhance the efficiency of BWS treadmill training. It consists in regulating the height of the BWS system to track the height of the subject's center of mass (CoM), whereby the CoM is estimated through a long-short term memory (LSTM) network and a locomotion recognition system. The LSTM network takes the walking speed, body-height to leg-length ratio, hip and knee joint angles of the hemiplegic subjects' non-paretic side from the locomotion recognition system as input signals and outputs the CoM height to a BWS treadmill training robot. Besides, the hip and knee joints' ranges of motion are increased by 34.54% and 25.64% under the CoM height regulation compared to the constant weight support, respectively. With the CoM height regulation strategy, the stance phase duration of the paretic side is significantly increased by 14.6% of the gait cycle, and the symmetry of the gait is also promoted. The CoM height kinematics by adjustment strategy is in good agreement with the mean values of the 14 non-disabled subjects, which demonstrated that the adjustment strategy improves the stability of CoM height during the training.

CLINICAL COURSE OF SCHIMKE IMMUNO-OSSEOUS DYSPLASIA AFTER KIDNEY TRANSPLANTATION

Schimke immuno-osseous dysplasia (SIOD) is one of the rare causes of steroid-resistant nephrotic syndrome. Extra-renal symptoms of this autosomal recessive disease include spondyloepiphyseal dysplasia, disproportional growth failure and defective cellular immunity. Kidney transplantation (KT) is indicated in these patients when their kidney problems progress to end-stage renal disease (ESRD). Due to the rarity of this condition, clinical course of SIOD after KT is not well known yet. Here we present our experience of SIOD after KT. Since 2014 three children with focal segmental glomerulosclerosis (FSGS) confirmed by biopsy were diagnosed as SIOD through genetic analysis. Onset age of proteinuria was 7, 5, 3 years, respectively. All of them had disproportional growth failure and typical facial feature. They reached ESRD in about two years after diagnosis of proteinuria. At their age of 9, 7, 9 years, these patients had living donor KT from their parents. After KT they suffered from multiple infections. Case 1 had PCP pneumonia requiring ventilator care 2 months after KT, then in 3 months disseminated adenovirus infection occurred along with CMV, EBV, and JC virus infection. The patient succumbed to the infection in 2 months despite aggressive management. Case 2 had CMV infection and PCP pneumonia after 3 months of KT. She suffered from skin infection and otitis. Case 3 suffered from respiratory failure due to CMV infection after 5 months of KT. Recurrent hospitalization was required due to various infections. Allograft has survived for 3.5 years in case 3 despite low-dose tacrolimus single medication (< 5ng/mL), but case 1 lost his graft function along with disseminated adenovirus infection. Case 2 had graft failure after 5 years of KT from acute rejection, probably due to insufficient dosage of tacrolimus and poor compliance. As Extra-renal presentation case 1 had renal vein thrombosis extended to IVC and pulmonary hypertension before KT, lowering his oxygen saturation to 80-90% in room air. Case 2 had severe developmental dysplasia of the hip requiring orthopedic surgery at the age of 5. She had sitting height and leg length ratio of 0.96, vertebral flattening and lordosis on spine x-ray suggesting spondyloepiphyseal dysplasia. After KT she suffered constant headache and Moyamoya syndrome was dignosed. She had an encephaloduroarteriosynangiosis when she was 10yrs 4month old. Case 3 suffered from spontaneous bacterial peritonitis and recurrent rhabdomyolysis along with neutropenia and thrombocytopenia before KT. In three years of KT his neutropenia and thrombocytopenia aggravated and bone marrow study suggested aplastic anemia. Hematopoietic stem cell transplantation is under consideration. In summary, SIOD is a rare systemic disease presenting as FSGS. While KT is indicated for their ESRD, their extra-renal symptoms progress regardless of KT. With its defective cellular immunity multiple infections complicate the clinical course after KT in SIOD.

Inter-regional differences in body proportions in Indian children and adolescents—a cross-sectional multicentric study

Background: Sitting height (SH) and leg length (LL) help in assessing disproportionate growth. Anthropometric dissimilarity has been observed in different ethnicities.Aim: To (1) study sitting height and body proportions in children from different regions of India; and (2) compare sitting height and body proportions with data from other countries.Subjects and methods: This was a cross-sectional multicentric observational study, where 7961 (4328 boys) 3–18 year old children from five regions (north, south, east, west and central) were measured (height, weight and SH).Results: Boys from north India and girls from central India were taller and heavier (mean height 153.2 ± 18, 146.4 ± 11), while western boys and girls were the shortest (131.1 ± 20.7, 129.8 ± 19.5) (p < 0.05 for all). The highest SH was observed in the north (79.2 ± 8.5) and the lowest in the west (68.8 ± 9.1). Mean SH:LL ratio was highest in children from the northeast (1.13) followed by those from western, northern and central India (1.12, 1.10 and 1.07, respectively) and the ratio was the least in children from south India (1.05) (p < 0.0.5 for all except northeast and west). Children from the north and west were similar to the Dutch, children from the south were similar to South (black) Africans and the north-eastern children were similar to Chinese children.Conclusion: There were inter-regional differences in body proportions; similarities in body proportions with children from other ethnicities may throw light on the migration history of Indian people.

Anthropometry Factors and Physical Dominan Conditions in Futsal Playing Capabilities

This study aims to find out to determine the anthropometric factors and dominant physical conditions in the ability to play female futsal. The population of this research is 14 female futsal teams at IAIN Purwokerto. This type of research is quantitative, using a Confirmatory Factor Analysis design. The data collection technique used in this study was by test and measurement. Data from the test results and measurements are then processed and calculated using the KMO and Bartlett's Test program. The results of the study obtained anthropometric factors that were dominantly influential in determining the performance of futsal athletes, namely the ratio of leg length and height. Factors of physical condition that are dominantly influential in determining the performance of futsal athletes are agility.

A new design of solar thermoelectric generator with combination of segmented materials and asymmetrical legs

In this work, a novel solar thermoelectric generator (TEG) design is proposed to enhance its output power and conversion efficiency. It combines segmented thermoelectric materials and asymmetrical legs with variable cross-sectional area along the leg length. A three-dimensional multiphysics thermoelectric model is employed to examine the performance of the new design. The optimal leg length ratio of two segmented materials (P1 and P2 materials) and the optimal cross-sectional area ratio of cold end to hot end are determined. In comparison with using P1 and P2 materials, the results show that the segmented design increases the output power by 14.9% and 16.6%, respectively, when the leg length ratio is optimized. When the asymmetrical legs are introduced to the segmented design, the output power can be additionally increased by 4.21%, as compared with the optimal segmented design. Moreover, a simple analytical model is proposed to predict the optimal leg length ratio of two thermoelectric materials for the present new design. The proposed model can be reduced to the existing models when the leg cross-sectional area ratio of cold end to hot end is equal to 1. Thus, the model can be considered as a generalized model, which can evaluate the optimal leg length ratio for the segmented design with any leg shape. Based on the model, the optimal leg length ratio should make the interface temperature between the two materials equal to the temperature of intersection point of their ZT (figure of merit) curves. Theoretically, this conclusion can be extended to any leg shape with a constant or variable cross-sectional area. The present simulations verify the theoretical prediction of the optimal leg length ratio.

Rural–urban variations in age at menarche, adult height, leg-length and abdominal adiposity in black South African women in transitioning South Africa

Background: The pre-pubertal socioeconomic environment may be an important determinant of age at menarche, adult height, body proportions and adiposity: traits closely linked to adolescent and adult health.Aims: This study explored differences in age at menarche, adult height, relative leg-length and waist circumference between rural and urban black South African young adult women, who are at different stages of the nutrition and epidemiologic transitions.Subjects and methods: We compared 18–23 year-old black South African women, 482 urban-dwelling from Soweto and 509 from the rural Mpumalanga province. Age at menarche, obstetric history and household socio-demographic and economic information were recorded using interview-administered questionnaires. Height, sitting-height, hip and waist circumference were measured using standardised techniques.Results: Urban and rural black South African women differed in their age at menarche (at ages 12.7 and 14.5 years, respectively). In urban women, a one-year increase in age at menarche was associated with a 0.65 cm and 0.16% increase in height and relative leg-length ratio, respectively. In both settings, earlier age at menarche and shorter relative leg-length were independently associated with an increase in waist circumference.Conclusions: In black South African women, the earlier onset of puberty, and consequently an earlier growth cessation process, may lead to central fat mass accumulation in adulthood.

A minimized falling damage method for humanoid robots

In order to better adapt to human living environment for improving the ability of serving people on various occasions, humanoid robots need to prevent themselves from being severely damaged during falling backward. In this article, we have study the law of human falling motion with a motion capture system and propose a minimized falling damage method for humanoid robots. Falling backward is divided into two phases: the falling phase and the touchdown phase. The parametric optimal strategy based on inverted pendulum with flywheel is used to plan the motion of robot in the first phase to reduce the impact. In the second phase, to prevent the robot from bouncing and rolling over, the heuristic strategy including the best ratio of leg length inspired by biomechanical is adopted. The experiments have been tested on the BIT Humanoid Robot 6 prototype platform and the presented method has been validated.

Combination of a biodegradable three-dimensional (3D) – printed cage for mechanical support and nanofibrous membranes for sustainable release of antimicrobial agents for treating the femoral metaphyseal comminuted fracture

The aim of this study was to develop a biodegradable three-dimensional-printed polylactide (PLA) cage for promoting bony fixation and an antibiotics-embedded poly(d,l)-lactide-co-glycolide (PLGA) nanofibrous membrane for infectious prophylaxis during treating the comminuted metaphyseal fracture in a rabbit femoral model. The in vitro studies included measuring the mechanical properties of the 3D printed cage and determining release activities of vancomycin and ceftazidime from the nanofibers. The in vivo study included comparisons of rabbits of the femoral metaphyseal comminuted fracture treated with or without the combined biodegradable polymers. The results showed that vancomycin and ceftazidime were sustainably detected above the effective levels in the local tissue fluid around the fracture site for 3 weeks. The animal studies showed that rabbits with the 3D cage implantation possessed better cortical integrity, leg length ratio, and maximal bending strengths. The study results indicate that these combined polymers may promote fracture fixation during treating the rabbit femoral metaphyseal comminuted fracture.

The association between social factors and body length proportions in Polish schoolchildren from Lower Silesia

Many studies worldwide have shown that social factors are significantly associated with growth in childhood. However, very few researchers studied influence of social factors on body length proportions. The aim of the present study was the assessment how urbanization level, sibship size and parental education may affect body length proportions in schoolchildren. 325 boys and 335 girls aged 7-18 years were measured in schools in Wrocław, two small towns and villages around these towns. Height, sitting height, leg length , and lower leg length were measured in all children, then relative lengths (in relation to height) were calculated: leg, femur, lower leg, estimated leg and lower leg length to leg length ratio. Height was standardized on age using LMS parameters for CDC 2002 year cohort. Other indices were standardized on age by using residuals variance derived from linear regressions. Four-way analysis of variance was used for height and each index, where independent variables were four social factors. Except for father’s education in boys, no other social factor was significant associated with height. Urbanization level significantly differed almost all indices, whereas father’s education level was significantly associated with relative leg length in girls and estimated leg length in both sexes. Our study has shown that the segments of lower limb seems to be more sensitive than height to the effect of social factors. In Lower Silesia, the level of urbanization is still related to differences in environmental conditions, enough to significantly affect growth of children, especially within the segments of lower limbs.

A comprehensive and time-efficient model for determination of thermoelectric generator length and cross-section area

A comprehensive mathematical model is proposed to calculate the optimal leg length and cross-section area of TEG unit to maximize the peak output power. The model shows that for a TEG unit, there exists an optimal ratio of leg length and leg cross-section area corresponding to the maximum peak output power with a convective thermal boundary condition, and the optimal leg length and cross-section area can be further calculated based on the optimal ratio. The mathematical model is also validated in this paper, and the corresponding error is within a reasonable range. Moreover, the effects of the leg length and leg area on the peak output power, the peak output power density and the efficiency of TEG unit with different thermal boundary conditions are also discussed. This study will provide guidance for the structure design optimization of TEG unit.

Enhancement of maximum temperature drop across thermoelectric cooler through two-stage design and transient supercooling effect

In this work, a new design concept which combines two-stage design with transient supercooling effect is proposed to enhance the maximum temperature drop across thermoelectric coolers (TECs). A three-dimensional, multiphysics, and transient model is used to examine the design effectiveness. Step current pulses with various amplitudes (P) and widths (τ) are supplied to the two stages of a two-stage TEC in series. The results show that, as compared with the single-stage counterpart, a significant improvement in the maximum cold-end temperature drop (ΔTc,max) is observed for the two-stage TEC. Meanwhile, the new design also greatly reduces the temperature overshoot (Tc,max) and increases the holding time of supercooling state (Δthold). Subsequently, effects of the pulse amplitude, width, and shape are discussed and two important geometry parameters: the cross-sectional area ratio of p-type leg to n-type leg and the leg length ratio of cold stage to hot stage are investigated. These results confirm that ΔTc,max, Tc,max, and Δthold can be further improved by optimizing the pulse and the geometry parameters. This work provides a feasible cooling approach for some specific cooling targets, such as mid-infrared laser gas sensors or any other semiconductor devices which require a temporary but large temperature drop.