Roof Angle Research Articles

Research on Deriving a Proportional System of a Roof Structure Through the Analysis of Hanok Architectural Design Methods

Hanoks are structures that have been built with unique techniques and styles since prehistoric times. Demand for hanoks is growing because they are recognized as climate-friendly buildings that make use of the natural environment as it is. However, there are a lack of standardized records concerning the methods or standards for constructing hanoks, so inferring them through the dimensional analysis of existing buildings is challenging. The roof of a hanok is its most beautiful part, and its proportions change the appearance of the hanok. Relying on existing examples or inherited figures when designing hanoks has led to the formation of uniform hanoks and the loss of their identity due to the lack of proportional standards. This study aimed to derive a proportional roof structure system by analyzing hanok architectural design methods. The employed method allowed for an analysis of the types of roofs and eaves of hanoks and extracted all the roof-related factors, such as the eave overhang, eave angle, roof angle, and hanok height. These data were compared with each other to find regularities and derive a final proportional system for a hanok roof structure. The analysis showed that the eave-height-to-roof-height ratio is 5.5:4.5, and notably, the sum of the eave and roof angles is in the range of 118°~120°, which means that the lower the eave angle, the higher the roof angle. Therefore, the roof structure of a hanok should not be designed based on a partial average value; rather, it should be based on a mutual proportional system considering the eave angle, roof angle, hanok height, and eave height. The results of this study can provide designers with a basis for creating hanoks through the use of the proportional system of roofs. This data basis guarantees continuity between the past and the present, and the proposed system can serve as a guide for hanok roof design and structural analysis.

Functional and radiological outcomes and complications of bernese periacetabular osteotomy through modified Stoppa approach.

The Smith-Peterson approach and its modifications provide an extensive exposure and allow osteotomies through a single incision. However, the risk of complications increases when the quadrilateral surface, ischial and pubic osteotomy sites cannot be seen. This study aimed to evaluate the surgical characteristics, complications, and functional and radiological outcomes of patients with acetabular dysplasia who underwent Bernese periacetabular osteotomy (PAO) through modified Stoppa approach and plate-screw fixation. The study included 31 patients (41 hips) who had undergone PAO using a modified Stoppa approach. The characteristics of patients and the surgical procedure were described. The lateral centre-edge angle (LCEA) and Tönnis roof angle were evaluated in the radiological outcome evaluation. The modified Harris Hip Score (mHHS) was used to evaluate functional outcome. Furthermore, complications were described. The mean age of the patients was 20.4 ± 9.0 years. Of the 31 patients, 21 underwent unilateral Bernese PAO and 10 underwent bilateral Bernese PAO. The mean follow-up period was 25.1 ± 8.8 months. Postoperatively, the mean mHHS improved significantly (68.8 ± 9.4 vs. 88.8 ± 10.0, p < 0.001). Postoperatively, the mean LCEA and Tönnis roof angle improved significantly (17.7 ± 6.0 vs. 42.2 ± 4.8, p < 0.001 for LCEA and 18.3 ± 5.5 vs. 8.0 ± 2.2, p < 0.001 for Tönnis roof angle). There was no significant correlation between preoperative to postoperative improvement in LCEA or Tönnis roof angle and improvement and mHHS (p > 0.005). 5 complications were identified: 1 transient sciatic nerve palsy, 1 external iliac vein injury, 1 infection, and 2 screw irritations of acetabulum. Performing Bernese PAO through a modified Stoppa approach with plate-screw fixation results in acceptable complication rates, immediate early weight-bearing opportunity, and improved functional and radiological outcomes in patients with acetabular dysplasia.

Fourth ventricular roof angle does not predict surgical outcome in paediatric patients with Chiari I malformation.

Pre-operative fourth ventricle roof angle (FVRA) has recently been highlighted as a novel radiographic predictor of clinical severity in Chiari type-I malformation (CM-I) as reported by Seaman et al. (J Neurosurg Pediatr 25:1-8, 2021). This has led to suggestions that FVRA could be included in algorithms to determine indications for surgery. We aimed to test the accuracy of FVRA as a predictor of clinical severity and its effect on post-operative outcome in a large retrospective cohort of paediatric patients who underwent decompression for CM-I. Patients undergoing craniocervical decompression for CM-I at the Queensland Children's Hospital and Mater Hospital, Brisbane, between 2006 and 2018 were included. Data was collected from 66 patients aged 0-18years. Post-operative outcome was assessed by calculating Chicago Chiari Outcomes Score (CCOS) at follow-up. The FVRA was taken from a mid-sagittal T1-weighted MRI as previously described (Seaman et al. in J Neurosurg Pediatr 25:1-8, 2021). The angle is subtended between superior and inferior medullary velum. Whilst results from Seaman et al. demonstrated a strong correlation between a FVRA > 65° and symptomatic CM-I, this did not translate to our dataset (p = 0.61). Additionally, pre-operative FVRA is not useful as a predictive tool for post-surgical outcome as assessed by CCOS (p = 0.50), and post-operative reduction in FVRA did not correlate with improved outcomes (p = 0.81). We did note significantly worse outcomes in patients presenting with pre-operative brainstem dysfunction (p = 0.03). Paediatric CM-I is a challenging cohort to manage, often due to young age and a lack of language skills. There is a heavy reliance on radiological findings. Whilst FVRA has previously been reported to be of value as a determinant of clinical severity in adult and paediatric patients, we find that this measurement is of dubious value in our retrospective cohort.

Characterization of tornado-induced wind pressures on a multi-span light steel industrial building

This study presents the characteristics of external wind pressures of a multi-span light steel industrial building through wind pressure measurements conducted in a tornado simulator. The test model is designed as a three-span low-rise building with gable roofs according to the practical measured sizes and shapes of the light steel industrial building destroyed in the Shengze tornado, China (2021). The distance from the tornado-like vortex center to the building, building orientation, roof angle, and swirl ratio are considered as experimental parameters. The effects of the parameters on the most unfavorable peak and mean pressure coefficients of each surface are analyzed. The roof zoning specified in ASCE 7–16 was re-analyzed based on the characteristics of wind pressure coefficients, and the tornado design pressure coefficients were calculated. The results of the analysis illustrate that the wind-ward roof surface at a distance of around one vortex core radius from the center experience the most severe pressure coefficient under tornado, the most unfavorable zone of the pressure coefficients on the building roof changes with the building orientation, the model with a smaller roof angle has smoother pressure coefficient contours than that with a larger roof angle because of the cutting effect of the ridge, and the simulated tornado with the lower swirl ratio generate higher external pressure coefficients on the building model. Moreover, the roof zoning in ASCE 7–16 for the boundary layer wind is not precise for tornado, thus an updated roof zoning for the tornado design pressure coefficients is defined.

CFD Analysis of the Generic Isolated Gable Roof Stadium: Impact of Opening Direction and Roof Angle for Wind Drift in Badminton

CFD Analysis of the Generic Isolated Gable Roof Stadium: Impact of Opening Direction and Roof Angle for Wind Drift in Badminton

Optimizing wind-catching butterfly roofs to improve cross natural ventilation performance in apartment buildings

Abstract This study aims to enhance cross natural ventilation performance in multi-level double-loaded apartments by employing a wind-catching butterfly roof, specifically designed for apartments with a center-to-center opening configuration. A 2k full-factorial design of experiment (DOE) method with a center point is utilized for design optimization. Nine configurations, determined by roof height h and roof angle α, are assessed using Computational Fluid Dynamics (CFD). After the initial DOE assessment, three additional butterfly roof designs with varying α values are explored. The dimensionless flow rate (DFR) serves as the objective function for optimization. The optimal design features a butterfly roof with h = 0.01m and α = 30°, demonstrating improvements of 2.5%−4.9% in DFR and 5.3%−9.0% in the pressure coefficient C p compared to scenarios without a butterfly roof. Butterfly roofs also increased the velocity magnitudes in the rooms of the leeward block, with configurations h = 0.01m and α = 35° and 37.5° showing the most significant increases of 58.5% − 86.9% on levels 1 to 3. The discharge coefficient C d induced by all butterfly roof configurations are within 0.6 − 0.7 on levels 1 to 3, while the C d values for levels 4 to 6 are within 0.5 − 0.6. Although butterfly roofs can enhance indoor air quality, they require further research to meet all recommended guidelines. These findings provide valuable insights for architects and urban planners aiming to reduce the environmental footprint of apartment buildings. This research presents a comprehensive evaluation of the potential of butterfly roofs to enhance apartment ventilation and offers recommendations for future design improvements.

A globalized methodology of energy-saving solar greenhouse design in high latitudes

The energy-saving solar greenhouse (ESSG) represents a Chinese-type agricultural building of facilitating low-energy and zero-carbon vegetable overwintering production in high latitudes and cold regions. However, its application benefit outside of China has been limited. To establish an operational ESSG design scheme applicable worldwide, this study developed a comprehensive methodology and specific parameters for different latitudinal regions. The ESSG design was determined based on considerations of daylighting, thermal insulation, heat storage-release capacity, and structural safety. Through validation in six representative regions, the reliability of the ESSG design methodology was confirmed. The optimal design values for front roof angle, ridge height, and back wall height were identified across different latitudes. ESSG in various latitudinal regions from 32°N to 48°N exhibited annual cumulative temperatures could reach 8 × 103∼1.3 × 104°C and accumulated light interception could reach 2 × 1012∼4 × 1012J. Even in the 48°N region, the average internal temperature of the greenhouse exceeded 8 °C, with a nighttime cooling rate lower than 0.75 °C/h and a maximum temperature difference between internal and external environments exceeding 40 °C. This suggests the ESSG fully meets the non-heated overwintering production requirements for common vegetables. The research findings provide crucial theoretical foundations for the global promotion of ESSG, contributing to the reduction of energy consumption and carbon emissions in the sustainable agriculture.

A 30-year follow-up study of rotational acetabular osteotomy for pre- and early-stage osteoarthritis secondary to dysplasia of the hip.

The objective of this study was to present the outcomes of rotational acetabular osteotomy (RAO) over a 30-year period for osteoarthritis (OA) secondary to dysplasia of the hip in pre- or early-stage OA. Between September 1987 and December 1994, we provided treatment to 47 patients (55 hips) with RAO for the management of pre- or early-stage OA due to developmental hip dysplasia. Of those, eight patients (11 hips) with pre-OA (follow-up rate 79%) and 27 patients (32 hips) with early-stage OA (follow-up rate 78%), totalling 35 patients (43 hips) (follow-up rate 78%), were available at a minimum of 28 years after surgery. In the pre-OA group, the mean Merle d'Aubigné score improved significantly from 14.5 points (SD 0.7) preoperatively to 17.4 points at final follow-up (SD 1.2; p = 0.004) and in the early-stage group, the mean score did not improve significantly from 14.0 (SD 0.3) to 14.6 (SD 2.4; p = 0.280). Radiologically, the centre-edge angle, acetabular roof angle, and head lateralization index were significantly improved postoperatively in both groups. Radiological progression of OA was observed in two patients (two hips) in the pre-OA group and 17 patients (18 hips) in the early-stage group. Kaplan-Meier survival analysis, with radiological progression of OA as the primary outcome, projected a 30-year survival rate of 81.8% (95% confidence interval (CI) 0.59 to 1.00) for the pre-OA group and 42.2% (95% CI 0.244 to 0.600) for the early-stage group. In all cases, the overall survival rate stood at 51.5% (95% CI 0.365 to 0.674) over a 30-year period, and when the endpoint was conversion to total hip arthroplasty, the survival rate was 74.0% (95% CI 0.608 to 0.873). For younger patients with pre-OA, joint preservation of over 30 years can be expected after RAO.

The Influence of Temporary Epiphysiodesis of the Proximal End of the Tibia on the Shape of the Knee Joint in Children Treated for Leg Length Discrepancy.

Background: Leg length discrepancy (LLD) is a common problem in the daily clinical practice of pediatric orthopedists. Surgical treatment using LLD temporary epiphysiodesis with eight-plate implants is a minimally invasive, safe, and well-tolerated procedure that provides good treatment effects with a relatively low percentage of complications. The main aim of this retrospective study was to determine the effect of epiphysiodesis on the shape of the proximal tibia. Methods: The retrospective study was based on medical records from 2010 to 2019. Radiographs taken before the epiphysiodesis and at 6-month intervals until the end of the treatment were investigated. A total of 60 patients treated for LLD were included in the study (24 girls, 36 boys). They were divided into three groups depending on the duration of the LLD treatment: group I (18 months), group II (30 months), and group III (42 months of treatment). Radiological parameters were assessed, including the roof angle (D), the slope angles (α and β), and the specific parameters of the tibial epiphysis, namely LTH (lateral tubercle height), MTH (medial tubercle height), and TW (tibial width). Results: The roof angle decreased in all the groups, which was accompanied by an increase in the β or α angle. LTH, MTH and TW also increased, and the differences before and after the treatment for the treated legs were statistically significant in all the studied groups. The greatest change in the shape of the articular surface of the proximal tibia occurred after 42 months of treatment. Conclusions: The study showed that epiphysiodesis affects the proximal tibial articular surface over prolonged treatment. Thus, there is a need for future long-term follow-up studies to elucidate the potential effects of LLD egalization.

Presenting new artificial intelligence techniques for finding optimum performance of solar chimney power plant

The various applications of solar energy have progressed significantly over recent decades. In this paper, finding the optimum performance criteria of a SCPP is studied. The mathematical modelling of 1-D flow is written and the optimum performance is determined for each group of geometric and environmental variables including the angle of collector roof (β), chimney divergence (α) and ambient wind velocity (Va ). In addition, different artificial intelligence techniques including regression tree, genetic programming and a novel method named trended regression tree are applied to find optimum performance conditions at any arbitrary group of α, β and Va . Results indicate that maximum power output (Pt ) and associated mass flow rate ( m ˙ ) increase with increasing chimney divergent angle and wind velocity at a constant collector roof angle. Comparing the obtained results of artificial intelligence techniques shows that trended regression tree method predicts the optimum conditions of SCPP better than other methods. Genetic programming is used to present fitted algebraic functions on Pt and m ˙ and the ratio of turbine pressure drop to pressure potential (PR). Results demonstrate the algebraic relation of PR estimates the PR accurately at each group of variables.

Optimization of Photovoltaic System Efficiency in Building Envelope Designs Using Genetic Algorithms: Comparative Analysis of Cost Metrics, Energy Savings, and Payback Periods

This study examines how genetic algorithms (GA) can be used to make protective structures for photovoltaic (PV) systems more efficient. We tried to increase the efficiency of solar cell systems in five different construction scenarios with regard to costs, energy savings, and payback time. To optimize this, we used construction parameters such as width, height, depth, insulation thickness, shading, and roof angle. An evolutionary algorithm generated the most efficient individual with parameters of 32.89 m width, 8.83 m height, 1.46 m depth, WWR = 32.52%, insulation = 8.96 cm, shading = 7.94 m², and roof angle = 72.08°. The solar panels had an efficiency of 31.27%. According to the cost analysis, Building 4, which had installation costs of $40,000 and annual maintenance costs of $1,500, provided the greatest energy savings of $7,000 per year and a payback period of five years. The features that distinguished Building 2 were installation cost, $ 25000; the pay back of installation was seven years; annual maintenance cost $ 800 per year. But it also saved less power which was around four thousand dollars for the year consumption. In Building 3 the greatest energy savings were found and pay back period was also five years In Buildings 3 and 5 average cost and performance was observed. According to the practical outcomes of the study, it has been perceived that applying of genetic algorithms can lead to enhancement of the economic efficiency of the solar power plants including energy saving aspects. It is therefore argued here that these skills can be applied to building design such that possible returns on solar panel systems are boosted.

Impact of acetabular roof's angle on precision of cup center of rotation reproduction and placement in total hip arthroplasty.

Total hip arthroplasty (THA) is nowadays considered as the most effective treatment option for end-stage hip osteoarthritis (OA) and one of the most successful orthopedic procedures. Precise reproduction of the center of rotation (COR) is among the most important aspects of recreating native hip biomechanics after THA as it is strictly related to muscle tension and force distribution within the hip joint. Both vertical and horizontal shift in cup positioning and COR restoration are commonly observed radiological signs corresponding with lesser functional outcome. The aim of this study was to assess whether the superior border of the native acetabulum morphology has an impact on cup positioning and COR restoration in patients undergoing THA as treatment of primary OA of the hip. A cohort of 150 consecutive patients with diagnosis of end-stage primary hip OA who underwent THA via an anterolateral approach with the same implant in 2021 was analyzed retrospectively. Standard standing pelvic X-rays were performed pre- and postoperatively and appropriate measurements were taken. Several radiological parameters on obtained X-rays were assessed. Statistical analysis of all the measurements was performed. There was a statistically significant positive weak correlation between cup offset and acetabular roof angle (rs = 0.25, p = 0.002). There were statistically insignificant positive correlations between acetabular roof angle and COR restoration (rs = 0.14, p = 0.097), acetabular roof angle and total offset (rs = 0.087, p = 0.29) and a negative correlation between acetabular roof angle and femoral offset (rs = 0.071, p = 0.39). The present study revealed that preoperative acetabular roof angle influences the positioning of the prosthetic cup in the transverse axis. There also seems to be a correlation between the acetabular roof angle and COR restoration, but its significance needs further evaluation. Surgeons could use this knowledge to preoperatively assess the risk of cup malposition and adjust their technique during the THA procedure with probable improvement of hip function.

Effect of Roof Design Configurations onNatural Ventilation with an Obstacle Inside the Building Model

Roof shape, roof angle, and internal obstacle are some of the factors that have a substantial impact on building's ventilation performance.However, previous roof ventilation studies havenot considered the influence of internal obstacle which canaffectthe overallbuilding’sventilation performance.Forthis study,CFD was used to studythe effect of roof design configurations on natural ventilation with an obstacle inside the building model. The numerical simulation was carried outbyusing steady RANS equation specifically the Standard k-ε with enhanced wall treatment. A total of 40simulationcases were carried out. The study considered two roof shapes mainly the sawtooth roof and the saltbox roof with varyingroof angle which were 10º, 20º,30º,and 40º. Internal obstacles with various height were further added into the simulation cases. Next, grid sensitivity analysis was carried out using Grid Convergence Index (GCI) and Factor of two of observations (FAC2) analysis was carried outas model verification methodto ensure a reliablesimulationresult. Based on the results, it is found that airflow characteristics such as wind speed, distributionof pressurecoefficient, and flowrate of an isolated building are strongly dependenton the roof shape and roof angle. Next, the dimensionless flowrate(DFR)is measured to be highest with largest roof angle while lowest with smaller roof angle. Furthermore, the DFR of a building with internal obstacle is lower than that without aninternal obstacledue to blockage of incoming air. Moreover, the results showthat the sawtooth roof outperforms the saltbox roof in terms of measured parameter.Finally, the study concluded that an isolated building with higher roof angle and without an internal obstacle leadsto the best dimensionless flowrate throughout the building.

Experimental study on the temperature distribution of impingement flow in a double slope roof generated by jet fire

The double slope roof is a commonly used building structure due to its adequate drainage and stable structural features. The thermal impinging on the double slope roof generated by the jet fire caused many casualties and property damage, whose thermal hazard has not been quantified in literatures. The temperature distribution at different source-ridge heights (H), heat release rates (HRR), and roof angle (θ) was measured in the experiment, with a total of 125 sets of experimental conditions. Results show that the ceiling maximum temperature rise increases with the roof angle decreases. A maximum temperature rise prediction model was established based on the analysis of the free plume length beneath the roof, which considering the effect of θ. Moreover, the model's accuracy was validated by comparing previous experimental data. The mean deviation between the proposed model and the experimental results is less than 5.7 %. The rate of temperature decay beneath the ridge decreased as the θ decreased. When the H is smaller, and the HRR is larger, the influence of the θ on the temperature decay profile is more significant. A new correlation has been proposed to correlate the temperature decay profile of a double slope roof with different θ by introducing flame extension length to modify the characteristic radius b. The model prediction agreed well with the experimental data, with a maximum error of around 20 %. New findings are helpful in guiding the building fire prevention and detection design.

Energy Saving Optimization of Commercial Complex Atrium Roof with Resilient Ventilation Using Machine Learning

Carbon-neutral architectural design focuses on rationally utilizing the building’s surroundings to reduce its environmental impact. Resilient ventilation systems, developed according to the thermal comfort requirements of building energy-saving research, have few applications. We studied the Jin-an Shopping Mall in Harbin and established the middle point height (h), middle point horizontal location (d), roof angle (α), and exposure to floor ratio (k) as the morphological parameters of the atrium. Using computational fluid dynamics (CFD), the mean radiant temperature (MRT), and the universal thermal climate index calculations (UTCI), this program was set to switch off air conditioning when the resilient ventilation met the thermal comfort requirement to achieve energy savings. The energy-saving efficiency (U) was calculated based on the energy consumption of the original model, and U could reach 7.34–9.64% according to the simulation and prediction. This study provides methods and a theoretical basis for renovating other commercial complexes to improve comfort and control energy consumption.

Limb length deceleration or coronal plane deformity correction using tension band plates: does plate configurations determine the intraarticular deformity of proximal tibia?

We studied whether the two-plate tension band configuration is more prone for intraarticular deformations than the single plate application used for coronal plane deformities (CPD). The study was based on radiological chart review (retrospective cross-sectional) of records of children [15 patients (30 plates) with limb length discrepancies (LLD) and 20 patients (36 plates) with CPD]. Interscrew angle, slope angle, and roof angle were compared in the initial postoperative and final radiographs to determine changes of tibial morphology. The mean patient age and follow up for the LLD and CPD groups respectively were 6.5 years, 39.8 months and 8.1 years, 15.5 months respectively. The interscrew angles widened between initial and final radiographs in the CPD group and for both sides in the LLD group. The initial and final slope angles were not significantly different in both LLD and CPD groups. Similar trend was observed for roof angle in either group. In the intergroup comparisons between LLD and CPD group, the slope angle of medial/lateral operated side in LLD group versus that of the operated side in CPD group matched statistically in the final radiographs. Similarly, the final roof angle in LLD and CPD groups was statistically similar. No significant intraarticular morphological change was demonstrated following tension band plating epiphysiodesis of the proximal tibia for our series involving young children. It was observed neither with the two-plate configuration used for limb length decelerations nor with the single plate application for coronal plane corrections.

Radiographic reference values of the central knee anatomy in 8–16-year-old children

Background and purpose: For correction of leg-length discrepancy or angular deformity of the lower limb in skeletally immature patients temporary or permanent (hemi-)epiphysiodesis can be employed. These are reliable treatments with few complications. Recently, radiographic analysis of treatment-related alterations of the central knee anatomy gained interest among pediatric orthopedic surgeons. To date the comparison and adequate interpretation of potential changes of the central knee anatomy is limited due to the lack of defined standardized radiographic references. We aimed to establish new reference values of the central knee anatomy.Patients and methods: A retrospective analysis of calibrated longstanding anteroposterior radiographs of 254 skeletally immature patients with a chronological age ranging from 8 to 16 years was conducted. The following radiographic parameters were assessed: (1) femoral floor angle, (2) tibial roof angle, (3) width at femoral physis, and (4) femoral notch–intercondylar distance.Results: All observed radiographic parameters were normally distributed with a mean age of 12.4 years (standard deviation [SD] 2, 95% confidence interval [CI] 12.2–12.6). Mean femoral floor angle was 142° (SD 6, CI 141.8–142.9), mean tibial roof angle was 144° (SD 5, CI 143.7–144.1), mean width at femoral physis was 73 mm (SD 6, CI 72.8–73.9), and mean femoral notch–intercondylar distance was 8 mm (SD 1, CI 7.5–7.7). The estimated intraclass correlation coefficient values were excellent for all measurements.Conclusion: This study provides new radiographic reference values of the central knee anatomy for children between 8 and 16 years and we suggest considering values within the range of 2 SD as the physiological range.

Comparison of mono and bifacial modules for building integration and electric vehicle charging: A case study in Sweden

Future energy systems have a major difficulty in ensuring a reliable supply of electricity without affecting the environment, and numerous innovative renewables-based solutions are being introduced to meet this issue. This paper proposes a building photovoltaic (PV) system design for residential and electric vehicle (EV) charging demand and evaluates the techno-economic and environmental performance of the system in Orebro, Sweden, as it aims to become net zero carbon economy by 2045. Literature review shows that, although many studies exist, most of them did not fully consider the techno-economic and environmental aspects of PV systems for residential and EV charging loads in the chosen location. Two different PV technologies monofacial and bifacial monocrystalline panel in three different roof slopes 15°,30° and 45° has been analyzed to find the optimized system that can meet a typical house's annual energy demand. Economic indicators such as cumulative cash flow, levelized cost of electricity (LCOE), payback period and cost of EV charging have been evaluated for the PV system without discount and with discount which affects the system's profitability. PVSyst software was used to simulate the system for energy generation. Results have shown that the bifacial PV system performed better in energy generation, which is approximately 10% higher than the monofacial panel. However, in terms of economics, Case 6, a bifacial PV system with a roof angle of 45°, shows the lowest payback period of 7.3 years. In contrast, monofacial PV system with roof slope of 30° showed LCOE of 0.8988 Swedish Krona per kilowatt hour (SEK/kWh), EV charging cost of 0.1471 Swedish Krona per kilometer (SEK/km). Environmental parameters such as greenhouse gases (GHG) reduction have been analyzed. Results showed that GHG savings due to EV was higher than PV plant as Sweden's grid emission factor is very low due to less dependency on fossil fuels. The significance of this study will enable us to understand the performance of PV systems in Swedish aspect and methods can be extended to other countries for meeting location-specific energy demand.

THIRTY-YEAR FOLLOW-UP STUDY OF ROTATIONAL ACETABULAR OSTEOTOMY

Satisfactory intermediate and long-term results of rotational acetabular osteotomy (RAO) for the treatment of early osteoarthritis secondary to developmental dysplasia of the hip have been reported. The purpose of this study is to examine the 30-year results of RAO.Between 1987 and 1994, we treated 49 patients (55 hips) with RAO for diagnosis of pre- OA or early-stage OA. Of those patients, 35 patients (43 hips) were available at a minimum of 28 years. The follow-up rate was 78.2% and the mean follow-up was 30.5 years. The mean age at the time of surgery was 34 years. Clinical evaluation was performed with the Merle d'Aubigne and Postel rating scale, and radiographic analyses included measurements of the center-edge angle, acetabular roof angle, and head lateralization index on preoperative, postoperative AP radiographs of the pelvis. Postoperative joint congruency was classified into four grades. The radiographic evidence of progression of OA was defined as the minimum joint space less than 2.5mm.The mean preoperative clinical score was 14.0, which improved to a mean of 15.3 at the time of the latest follow-up. The mean center-edge angle improved from 0.6° preoperatively to 34° postoperatively, the mean acetabular roof angle improved from 28.4°preoperatively to 1.0°postoperatively, the mean head lateralization index improved from 0.642 preoperatively to 0.59 postoperatively. Postoperative joint congruency was excellent in 11 hips, good in 29 hips, and fair in 3 hips. Nineteen patients (20 hips) had radiographic OA progression, and 10 patients (11 hips) were converted to THA. Kaplan-Meier survivorship analysis, with radiographic OA progression as the end point, predicted survival of 75.6% at 20 years and 48.8% at 30 years, and with THA conversion as the end point, 90.2% at 20 years and 71.2% at 30 years.The RAO is an effective surgical procedure for symptomatic dysplastic hips of pre- and early-stage OA and could change the natural history of the dysplastic hip.

Flame extension lengths beneath a double slope roof induced by gaseous fuel jet flame

Due to the characteristics of good drainage and stable structure characteristics, the double slope roof is widely used in civil houses, industrial plants, and ancient buildings. However, double slope roof fire accidents occurred frequently. Studying the flame characteristics under the ceiling can provide scientific guidance for building fire protection. The present study investigated the flame extension lengths beneath a double slope roof induced by gaseous fuel jet flame, which had not been quantified in the literature. Results show that the length of flame extension was longer in the ridge direction compared to the slope direction, with a maximum difference of approximately two times. Moreover, their deviation increases with larger HRR and smaller θ, resulting from the fact that the structure of the double slope roof would restrict air entrainment and induce more unburned gaseous fuel to spread along the ridge. Comparing the experimental data with previous models proves that they cannot predict the ceiling flame extension length under the influence of roof angle. A new correlation incorporating the effect of θ was established based on the proposed flame volume assumption to estimate the equivalent HRR at the ceiling, whose accuracy and reliability were further validated by reference data. The model prediction agreed well with the literature data, with a maximum error of around 20%.