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Purpose: The sequential combination of AI algorithms, or problem-solving commands, can increase aware-ness of battlefield situations. This article...

Construction safety climates can reflect organizational safety behavior and commitment, employees’ safety perceptions and attitudes, and the supervisory and support environments. Maintaining a healthy safety climate can help prevent workers from fatal accidents and illnesses. To enhance the safety climate and, consequently, improve safety performance at a construction site, it is very important to analyze the elements that affect the safety climate and are significant for different types of construction work organizations. Therefore, the main goal of this study was to develop a multi-spectra perception model to investigate which factors were considered critical from four key perspectives: managers, superintendents, skilled laborers, and general helpers. To achieve this goal, a survey questionnaire was conducted to collect empirical data from one commercial building construction project. Based on a stepwise regression analysis, it was revealed that the most significant factors enhancing the safety climate are: from the managers’ perspective, a combination of improvement in the support environment and reduction in work pressure; for superintendents and skilled laborers, increasing worker competence; and for general laborers, increasing worker involvement. This research contributes to a better understanding of the significant factors and provides a measure for each important role in enhancing the safety climate at a job site.

An experimental investigation of heat and mass transfer in a horizontal-tube falling-film ammonia-water absorber, operated as part of a complete ammonia-water absorption test facility, is presented. A tube bank consisting of four columns of six 9.5 mm nominal outer diameter, 0.292 m long tubes was installed in an absorber shell that allowed flow visualization and heat and mass transfer measurements at component- and local-levels. The Falling-film mode was found to account for a major portion of the absorber. The effects of operating conditions on the heat and mass transfer coefficients were investigated. While the solution Nusselt number increased, the vapor and liquid Sherwood numbers remained relatively insensitive to the solution Reynolds number. Heat and mass transfer models were developed to predict the absorber performance over a wide range of operating conditions in air-conditioning and heat pumping modes (solution concentration: 5–40%, pressures: 150, 345, 500 kPa, and solution flow rates: 0.019–0.034 kg s−1).

For application to all-solid-state thin film batteries, lithium boron phosphorus oxynitride (LiBPON) thin films were fabricated by RF magnetron sputtering technique of lithium borate (Li 3 BO 3 ) and lithium phosphate (Li 3 PO 4 ) target under N 2 atmosphere. To investigate the mixed former effect upon the LiBPON thin films, we prepared various films with controlled B and P contents. The LiBPON thin film formulation with nearly equal B and P contents showed the highest room-temperature lithium ionic conductivity of 3.52 × 10 −6 S cm −1 and the lowest activation energy of 48.24 kJ mol −1 owing to the mixed former effect, the increased lithium content and nitridation. Infrared spectra of the glass thin films achieved two dominant peaks corresponding to BO 3 3− and PO 4 3− unit. N1s spectra were analyzed by X-ray photoelectron spectroscopy that the increased ionic conductivities observed were related to the formation of triply coordinated nitrogen.

To enhance the packing density of composite cathode for all-solid-state lithium-ion batteries, the effect of a bimodal sized solid electrolyte was studied. The composite cathode, which is fabricated using the powder compression method, consisted of the cathode active material, a conductive agent, and the solid electrolyte. However, the composite cathode construction had voids. The voids in the composite cathode were restricted to ionic conduction between the cathode active materials and the solid electrolytes. Suppression of the voids in the composite cathode improved the electrochemical performance of the all-solid-state battery. A composite cathode using bimodal sized electrolyte powders demonstrated better cell performance than that using only fine or coarse sized electrolyte powders. These results demonstrated that the composite cathode using the bimodal sized electrolyte enhanced the electrochemical performance of the all-solid-state battery because it improved the packing density of the cathode.

High-strength concrete (HSC) uses binders and microfillers with ultrafine particles, such as silica fume. The resulting dense internal hydration structure rapidly decreases HSC humidity, causing shrinkage cracks and affecting internal hydration. Herein, the hydration degree inside high-strength cement composites (HSCCs) was examined using waste glass beads (WGBs) as lightweight aggregates (LWAs). Moreover, unreacted hydrate reduction and hydrate formation tendencies were investigated. WGBs with particle sizes within 2.00–6.00 mm were added at ratios of 5%, 10%, and 20% after pre-wetting. The increased number of hydrates inside the specimens were examined under steam curing (80 °C) and room temperature curing (25 °C). The strength decreased as the WGB content increased. Thermogravimetric, X-ray diffraction, and Si nuclear magnetic resonance analyses revealed that the hydration degree of Si inside HSCCs changed when the content of pre-wetted LWAs changed. A visual inspection of the specimen cross-section and scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) analysis revealed the moisture trapped inside WGB pores and the hydration tendency. Under steam curing and room temperature curing, the paste contained different amounts of hydrates, depending on WGB content. Moreover, water-absorbed WGBs were continuously desorbed through SEM–EDS, and hydrates were present in WGB pores.

Research has shown that both gender and family socioeconomic status (SES) are important determinants of adolescents' physical activity (PA). This study expands our current knowledge by exploring the moderating role of family SES on gender differences in adolescents' out-of-school PA. We also examine whether this moderating effect varies across countries with different levels of gender inequality. Based on existing empirical studies and theoretical framework, it is hypothesized that 1) gender differences in out-of-school PA would be smaller among adolescents from higher SES families due to them being more likely to share egalitarian gender norms, and 2) this SES gradient in gender differences in adolescents' out-of-school PA would be more salient in countries with lower levels of gender inequality. A total of 316,657 15-year-old adolescents in 50 countries from the 2015 Programme for International Student Assessment (PISA) survey were analyzed. Our multilevel negative binomial regression models show that the gender gap in out-of-school PA is mitigated among families with higher SES, but this moderating role of family SES is less noticeable in countries with higher levels of national gender inequality. Our findings suggest the importance of egalitarian gender culture at both individual and macro-level in understanding gender disparities in adolescents' PA.

In microscale photogrammetry, the confocal microscopic imaging technique has been the dominant trend. Unlike the confocal imaging mostly for transparent objects, we propose a novel method to construct a 3D shape in microscale for various micro-sized solid objects in a broad spectr&micro, m of applications. Recently, the structure from motion (SfM) demonstrated reliable 3D reconstruction capability for macroscale objects. In this paper, we discuss the results of a novel micro-surface reconstruction method using the Structure from Motion in microscale. The proposed micro SfM technique utilizes the photometric stereovision via microscopic photogrammetry. The main challenges lie in the scanning methodology, ambient light control, and light conditioning for microscale object photography. Experimental results of the microscale SfM, as well as the modeling accuracy analysis of a reconstructed micro-object, are shared in the paper.

Atomically smooth, single crystalline Bi 2 Se 3 thin films were grown on a Ge(1 1 1) substrate using molecular beam epitaxy. Crystallinities of both the surface and the bulk as well as the stoichiometry of the grown film were characterized by using low-energy electron diffraction, scanning tunneling microscopy, X-ray diffraction, and photoelectron spectroscopies. Hexagonal atomic structures, quintuple layer steps observed in STM images confirmed that the Bi 2 Se 3 film with a (0 0 0 1) surface was grown. Diffraction peak positions as well as the chemical composition determined from the core-level photoelectron spectra coincide well with those expected for the Bi 2 Se 3 crystal. The surface state with a Dirac cone was observed in the valence photoelectron spectra, which also support that a high-quality Bi 2 Se 3 film was grown on the Ge(1 1 1) substrate. The interface between Ge(1 1 1) and Bi 2 Se 3 (0 0 0 1) is expected to be abrupt due to the small lattice between them.

All-solid-state lithium ion batteries (ASSLIBs) are very promising next-generation lithium ion batteries with high energy density and safety. Among the solid electrolytes that can be applied to ASSLIBs, sulfide glass-ceramics electrolytes are attracting attention because of their high ionic conductivity and good mechanical deformability. However, the lack of the chemical and electrochemical stability of the sulfide electrolytes under prolonged cycle operation has become a barrier limiting their practical use and commercialization. We investigated the effects of Sn substitution on the electrochemical and chemical stability enhancement of Li2S-P2S5 glass-ceramics electrolytes. Also, we analyzed the cause of the degradation by side reactions and lithium dendrite growth. For 80Li2S-15P2S5-10SnS2 glass-ceramics electrolyte, only the redox current of the lithium deposition/dissolution was observed in cyclic voltammetry test with lithium metal. And the result of X-ray photoelectron spectroscopy analysis demonstrated a reduction in the amount of Li2S and decomposition product from the sulfide solid electrolytes. ASSLIBs using 80Li2S-15P2S5-10SnS2 as solid electrolytes with Li metal or Li-In anodes showed improved cycling performance compared to batteries employing 80Li2S-20P2S5 glass-ceramics. These results showed that Sn substitution is effective to improve the chemical and electrochemical stability of Li2S-P2S5 glass-ceramics electrolyte to lithium metal.

The influence of Pb atoms adsorbed on an In/Si(111) surface on the phase transition was investigated by using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). LEED data showed that the transition temperature for the 4×1 → 8×2 structural phase transition decreased in proportion to the amount of Pb deposition. The Pb adatoms appeared as bright protrusions in an STM image taken at 90 K, suggesting that they were located high above the In atomic wires. The regions surrounding the Pb adatoms remained in the 4×1 phase while the other areas turned into the 8×2 or 4×2 phase at this temperature below the transition temperature. Near each Pb adatom, a Friedel-oscillation-like modulation with a double (×2) periodicity in the wire direction was developed. This ×2 modulation was found to be different in nature from the low-temperature 8×2 (or 4×2) phase. We suggest that a Pb-adatom-induced deep potential well is responsible for the Tc lowering and the ×2 modulation.

Recent leaps in heat dissipation make it difficult for typical heat exchangers to meet the requirements of the advanced applications even with the maximally obtainable heat transfer performance associated with a single-phase process. Especially high heat flux applications such as thermal management in microelectronics, advanced material processing, and nuclear fusion reactors require extreme heat transfer methods to overcome the current limits. In this study, a heat exchanger adopting simultaneously two-opposite, phase-change heat transfer processes (internal flow boiling and external condensation) was proposed and analytically investigated. The phase-change heat transfer analyses were conducted for internal flow boiling and external condensation at a test section and the heat transfer performances were compared with that of a system with an internal single-phase, liquid flow process. It is found that the proposed heat exchanger configuration with an internal flow boiling can substantially enhance the heat transfer performances and provide better methods to manage the temperature difference comparing to those with an internal single-phase heat transfer due to its significant increase in a heat transfer coefficients and constant temperatures during phase-change processes. Additionally, this study also explains the design for a test rig to evaluate and validate the results in detail. The test rig consists of an internal flow boiling loop with a test section, an external condensation loop, sensors, auxiliary monitoring parts, and controlling and data acquisition systems. Thermodynamic cycle, pressure drop, and heat transfer analyses were conducted to determine the conditions and the specifications of components and sensors for the test rig.

PURPOSES : This study aimed to develop a new highway capacity estimation method and provide comparative results among traditional capacity estimation methods and the recommended values in the latest version of KHCM. METHODS : The limitations of the existing methods, such as inconsistency and underestimation of the capacity value, are summarized through an extensive literature review. To overcome these limitations, a new method is introduced by adopting a definition of capacity and traffic flow characteristics at or near breakdown points. This method can produce the capacity value by searching a point corresponding to the maximum traffic flow through analysis of gradient changes (point of inflection) of the traffic flow and speed distribution. Comparative results of capacity values from each method are also presented to validate the new method by using data collected from detectors on freeways. RESULTS: From the analysis results, it is shown that a consistent capacity value can be estimated by applying the new method. In addition, the resulting capacity values are 3%-4% higher than those recommended in KHCM. CONCLUSIONS : The capacity values listed in the current KHCM tend to produce underestimated results. The new method presented in this paper may be included in the future edition of KHCM.

PURPOSES : This study evaluated the feasibility of implementing protected-permissive left-turn (PPLT) signals at three-leg signalized intersections. METHODS: A three-leg signalized intersection with permissive left-turn was first selected. A VISSIM simulation model was constructed using data collected from the test site. The VISSIM network was calibrated by adjusting related parameter values in order to minimize the difference between the simulated and surveyed critical gap. The calibrated network was validated by the number of waiting left-turning vehicles per cycle. Finally, the mobility and safety measures were extracted from simulation runs in which permissive, protected left turns as well as PPLTs were realized based on diverse traffic volume scenarios. RESULTS : The mobility-related measures of effectiveness (MOEs) of the case with PPLT outperformed the other two left-turn treatment scenarios. In particular, the average waiting time per cycle for the left-turn vehicles in the case with PPLT was reduced by 30 s. The safety-related MOEs of the case with PPLT were somewhat higher than those in the case with protected left-turns and much higher than those in the case with permissive left-turns. CONCLUSIONS : Based on the mobility- and safety-related MOEs generated from the VISSIM simulation runs, the use of PPLT seems to be feasible at three-leg signalized intersections where the left-turn is permissive and a pedestrian signal exists at the conflicting approach. However, in order to use the PPLT in earnest, it is necessary to revise the road traffic act, traffic signs, and related manuals.

PURPOSES: This study analyzes the characteristics of traffic flow on freeway sections under daytime and nighttime conditions to improve traffic safety, and suggests a method to estimate an accurate freeway capacity value that reflects these characteristics. METHODS : The trends and differences in capacity were investigated using comprehensive field data collected under both daytime and nighttime conditions on freeway sections with designated speeds of 80, 100, and 120 kph. RESULTS : The capacity values under nighttime driving conditions were reduced by 3.3%, 6.9%, and 8.8% at 80, 100, and 120 kph, respectively. Several nighttime adjustment factors were deduced for each designated speed category from the analysis results. CONCLUSIONS : It is expected that more accurate capacity values can be estimated for freeway sections under nighttime conditions by applying the resulting adjustment factors. In addition, traffic safety will be improved through the increased efficiency of traffic management on these freeway sections.

PURPOSES : This study aims to investigate the direct and indirect influence areas from incidents on urban interrupted roadways and to develop traffic management strategies for each influence area. METHODS : Based on a literature review, various traffic management strategies for certain incidents were collected. In addition, the relationship between the measure of effectiveness and the characteristics of incidents was explored using an extensive simulation study. RESULTS : From the simulation studies, traffic delays increased as the number of lane closures increased, and the impact of lane closures was reduced to the direction upstream from the incident site. However, the magnitude of the delay change depended on the degree of saturation. Using these characteristics, the direct and indirect influence areas resulting from incidents were defined, and traffic management strategies were established for each direct and indirect influence area and for each level of incident. CONCLUSIONS: The results of this study will contribute to the improvement of national traffic safety by preventing secondary incidents and by effective adaptation to incident events.

Many researches have been focused on internal condensation with machined microstructure patterns on internal surfaces that can improve heat transfer performance up to 400% comparing to smooth surfaces. However, microstructure patterns are not effective for all geometries such as micro-channels and other complicated shapes. This study uses a dropwise condensation (DWC) promoter that can be easily applied to different geometries to improve internal condensation heat transfer. The main objectives of this study are to investigate internal condensation heat transfer by the dropwise condensation promoter via (i) developing an internal dropwise condensation model and (ii) conducting internal condensation experiments with the dropwise condensation promoter. The dropwise condensation model was modified to the available internal condensation model. The experiments for internal steam condensation were conducted for aluminum and copper tubes with external fins and an internal coating for dropwise condensation. The experimental results are compared to the results from several correlations in the literature and the model developed in this study. It is found that most correlations in the literature overestimate internal condensation heat transfer coefficients at low mass fluxes. The dropwise condensation model shows that dropwise condensation promoters can enhance internal condensation heat transfer coefficients. This conclusion is verified by experimental results demonstrating that the hydrophobic dropwise condensation promoter used in this study can enhance internal condensation heat transfer coefficients by 50%.

A two-step annealing method with a low thermal budget is proposed for advanced surface-energy-driven secondary grain growth of Ge films without any agglomeration. In the first-step annealing, the normal grain growth from as-deposited poly-crystalline Ge films was induced to make the grain size equivalent to the film thickness at 800 °C. After the subsequent second-step annealing at 900 °C, the much larger secondary grains were obtained than those by single-step annealing at 900 °C. The possible explanation regarding the final microstructure of the two-step annealed film is proposed. The two-step annealing was able to form the microstructure of Ge thin film with very large-grained matrix without any agglomeration, resulting in higher carrier mobility. Therefore, the proposed two-step annealing is believed to be a promising process applicable for channel formation processes in the next-generation Ge thin film transistors for 3D integrated circuits and vertical NAND flash memories.

In this paper, travel speed patterns were deducted based on historical DSRC travel speed data using Decision Tree technique to improve availability of the massive amount of historical data. These patterns were designed to reflect spatio-temporal vicissitudes in reality by generating pattern units classified by months, time of day, and highway sections. The study area was from Seoul TG to Ansung IC sections on Gyung-bu highway where high peak time of day frequently occurs in South Korea. Decision Tree technique was applied to categorize travel speed according to day of week. As a result, five different pattern groups were generated: (Mon)(Tue Wed Thu)(Fri)(Sat)(Sun). Statistical verification was conducted to prove the validity of patterns on nine different highway sections, and the accuracy of fitting was found to be 93%. To reduce travel pattern errors against individual travel speed data, inclusion of four additional variables were also tested. Among those variables, `traffic condition on previous month` variable improved the pattern grouping accuracy by reducing 50% of speed variance in the decision tree model developed.