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Odontogenic keratocyst (OKC) accounts for 3-11% of all odontogenic cysts. OKC is a benign intra-osseous odontogenic tumor, but what makes this cyst special is its aggressive behavior and high recurrence rate. OKC is relatively aggressive compared to other odontogenic cysts, but its malignant transformation is considered extremely rare. Squamous cell carcinoma associated with odontogenic keratocysts have rarely been reported in the medical literature. We recently experienced a case of a 63-year-old man finally confirmed with squamous cell carcinoma of the mandible, which was initially diagnosed as a benign odontogenic keratocyst. Surgical resection was performed as definitive treatment. Therefore, we present this unique case with a review of the literature.

Design education has significantly changed since the 1950s. The era depended widely on normative models such as those proposed by Benjamin Bloom (Bloom et al. 1956) and his collaborators, which resulted in the formulation of Bloom's Taxonomy. Comprising six interchangeable layers (knowledge, comprehension, application, analysis, synthesis, and evaluation) of higher and lower thinking, Bloom's taxonomy sets in place an archetypal model for education that thrives on object-driven goals. Here, pedagogical interchange and the object-driven and organised structure of education can adapt to each layer within the taxonomic structure.

Concrete is one of the most widely used structural construction materials and has significantly influenced industrial development [...]

In the theme park industry, returning visits are often considered a measure of success. Numerous parks have incorporated virtual reality (VR) technology to encourage visitors to return. This paper ...

PurposeThe novel coronavirus (COVID-19) has completely changed the landscape of the hospitality industry. The World Health Organization does not officially recommend wearing face masks in the workplace. Wearing face masks is controversial worldwide, however it has been widely adopted in Hong Kong society. Hospitality practitioners have worn face masks to work and serve customers for almost a year long, matching the duration of the COVID-19 pandemic. This paper proposes a conceptual model of face mask effects and also discusses and evaluates the effects of wearing face masks during the pandemic.Design/methodology/approachA convenience sampling method is employed to investigate hospitality operators using in-depth and focus group interviews with managers, front-line staff and customers.FindingsThe perspectives of both hospitality practitioners and customers are included in this study. The concepts of (1) invisible care, (2) sense of safety and (3) service trust have been introduced in this study. These provide valuable insights for the service industry when facing a large-scale health crisis, now and in the future.Research limitations/implicationsThis paper analyzes interview data collected from 35 respondents – 14 managers, 6 practitioners and 15 customers – in order to understand the critical effects of wearing face masks during the pandemic and the perspectives of both hospitality practitioners and customers.Practical implicationsFor the hospitality industry, wearing face mask in service has already become a “new normal”, face mask effects might create an impact on service design, service delivery and service quality.Originality/valueThe findings show that wearing face masks turns hygiene and safety into a form of invisible care in the Asian hospitality industry. Practitioners' perspective regarding the necessity of a smile is less important to Asian customers, showing a discrepancy between the two parties. Customers do not believe that service quality has dropped due to the wearing of masks, but that the level of hygiene has risen. Unlike customers, practitioners are more concerned about not providing good quality service. However, the interview data show that respondents generally agree that mask wearing is a gesture and symbol for the hospitality industry to make tangible a new form of caring, professionalism, safety concern and communication.

An online survey was conducted to examine how nostalgias associated with Hayao Miyazaki's animations motivate tourists to visit a theme park inspired by the director's works. A structural equation modeling of the collected data revealed that the survey respondents who felt nostalgic about the characters, narratives, aesthetics, cultures, and traditions depicted in the animations showed a strong motivation to visit the theme park, which then positively influenced their attitude and behavioral intention to visit the park in the future. The study findings provided empirical evidence for validating nostalgia as a multidimensional concept and its vital role in promoting film tourism.

University-level classrooms have seen a massive transformation from instructor-led to student-centered education, with many courses adopting project-based learning as an effective learning approach. As students become key actors in leading their courses, it is necessary to have high-level intrinsic and extrinsic motivation. In the search to enhance student motivation using project-based learning, this article proposes a framework based on self-determination theory, including various indicators of the level of students’ motivation for learning. In particular, the framework was applied to explore the effectiveness of employing social media, such as Facebook, to increase student motivation. The results of this study demonstrate the usefulness of employing social media to amplify students’ will to learn. This article reports on the results of action research in creative media design courses where students were required to develop an e-portfolio through Facebook. Eleven indicators (autonomy, confidence, eagerness to learn, high performance, independence, enjoyment, self-efficacy, sense of achievement, sense of belonging, sense of engagement, and sympathy) were used to measure motivation. As a result, this study argues for the conditional use of social media in project-based learning classes.

When we first initiated a call for this issue on design education, never could we have imagined or foreseen what lay ahead. Since late 2019, Hong Kong has gone through an enormously difficult time. First, spikes of social unrest, rapidly followed by COVID-19. Half of the first semester of the 2019 – 2020 academic year, as skirmishes closed in on The Hong Kong Polytechnic University campus, all courses had to move over to available and often misunderstood online platforms. As the situation finally subsided, the virus emerged, impacting the commencement of the second semester, and the overall delivery modes of a structured curriculum for an entire year. Both faculty and students of the School of Design lived and worked in high hopes to return to faceto- face teaching sooner, rather than later. In time, hope conceded to a stark reality that online, the virtual and the digital models of education, have moved into focus as the main and primary modes of education. Long gone are the days of the digital as a mere supplemental or peripheral possibility. The digital reality presented other challenges to design education: ensuring credible and authentic outcomes for each of the design disciplines within a non-studio setting, the expression of ideas, or demonstrating principles across and through digital platforms with the additional burdens of a digital generation that instantaneously become camera shy. Or, in the extreme the mistrust shown by students that reviewers may not understand the design work without a physical presence. Moving one year forward, the growing pains of digital pedagogies has caused an instantaneous maturing of educators, those being educated, and of what is said, shown and discussed. Somehow, the global body of design environments have collectively responded to these and more local challenges, yet again transforming the specifics of digital pedagogies across unexplored territories. The following series of images attest to the resilience of digital pedagogies and design institutions. May this stand as a testament to rapid responses, individuals who took the reins, and how educators shape the future of design, design-research and ultimately how design is carried forward across generations.

Diagnostic technologies using X-rays and/or acoustic emissions for concrete infrastructures containing internal pores, defects, and cracks have attracted considerable interest. However, computerized tomography (CT) for concrete is challenging due to its radiation shielding characteristics. Electrical impedance tomography (EIT), initially developed for medical use, has recently shown a potential for developing a macro-CT technique for concrete structures. This study derived EIT analytical solutions for rectangular cement-based samples and validated them with experimental data obtained from cubic mortar samples. The experimental validation of the three mathematical functions (Dirac delta, Heaviside step, and Gaussian) used as current injection models, the Gaussian function produced the lowest relative absolute error (4.02%). This study also explored appropriate experimental setups for cement-based materials, such as Shunt model, current flow paths, and potential distribution.

The influence of the added nitrate salts (Ca(NO3)2 and NaNO3) on the CaO-activated ground granulated blast-furnace slag (GGBFS) system was investigated. Both salts significantly increased the early strength of the binder, and the Ca(NO3)2 maintained this tendency until 28 days of curing, whereas NaNO3 did not. At early days, the NaNO3 likely increased pH of samples, resulting in more dissolving GGBFS and formation of C-S-H, while the Ca(NO3)2 slightly decreased pH due to the common ion effect, but because the Ca(NO3)2 supplied additional Ca ions, it also increased the strength. At 28 days, the NaNO3 clearly induced the reduction in C-S-H, which was not the case for the Ca(NO3)2 samples. In addition, the pore size distribution was also significantly dependent on the cation type of nitrate salts.

This study investigated whether three formate salt additives (Ca(HCOO)2, NaHCOO, and KHCOO) could improve the strength of a CaO-activated fly ash (FA) system. Various tests were conducted to verify the effects of the formate salts including compressive strength, X-ray diffraction (XRD), thermogravimetric (TG) analysis, solid-state 27Al magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, and mercury intrusion porosimetry (MIP). The results showed that the addition of Ca(HCOO)2 significantly strengthened the FA binder system by (1) substantially increasing C-S-H formation and (2) measurably reducing overall pore size. However, adding NaHCOO or KHCOO was much less advantageous to strength improvement because although helpful in dissolving FA, the high pH environment caused by their reaction with CaO inhibited further dissolution of CaO, which was the main activator used in this study.

This study reports the temperature-dependent strength improvement and retardation in Ca(OH)2-Na2CO3-activated fly ash binders with sugar. Without sugar, the system exhibited rapid stiffening due to the calcite formation. The addition of sugar clearly removed the false set; however, at room temperature, it retarded strength development because the calcium complexation of sugar inhibits the dissolved calcium ions from participating in calcite and C-S-H formation. However, at 90 °C, the use of sugar significantly improved the compressive strength by increasing the (1) degree of dissolution of fly ash and Ca(OH)2, (2) C-S-H formation, and (3) reduction of overall pore size and volume.

Interviews with experts and visitors conducted using a convenience sampling method were combined with archival research to understand the effect of adding VR technology to Korean theme park attractions, as well as to look at how nostalgic attributes in animation content can enhance the immersive experiences of the visitors. The interviews showed that having sophisticated, narrative driven, high-quality content is more important to visitors than the extent to which the VR technology is state-of-the-art. Findings also suggest that adopting existing well-known animation content to VR attractions will result in visitors experiencing better emotional connectedness, enhanced presence, and fuller immersion. Finally, ensuring that the quality-driven VR content evokes nostalgia will lead to repeat visitation by visitors.

This study explored the possibility of using limestone fines (LF) as a supplementary material in activated slag binder systems using two types of activators (i.e., 10 wt% of Ca(OH)2 or 10 wt% of Ba(OH)2) and investigated the interactions of the activators with LF in each binder system through strength testing, powder X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry. Using these binders, concrete brick samples containing LF were also made and examined for possible industrial applications. Although the influences of the LF addition on the strength, dissolution degree of the slag, reaction products, and pore-size distribution depended on the type and dosage of the activator, the addition was generally advantageous for all these aspects in both types of activations. The concrete brick made of 20 wt% LF using the Ba(OH)2 activation fulfilled the Korean standard requirements of strength and water absorption for concrete bricks, and it also satisfied the criteria of the leaching test for possible toxic elements.

This study reports the significant effect of CaCl2 on strength improvement in CaO-activated Class F fly ash system. In these systems, the presence of CaCl2 promotes (1) a higher degree of fly ash dissolution, (2) increasing C-S-H formation, and (3) an overall reduction of pore size and volume, resulting in increased strength. However, while more C-S-H, which is responsible for strength increase, was produced with higher CaCl2 content, extreme doses of CaCl2 resulted in strength degradation; more importantly, the best quantity of CaCl2 for the greatest strength was dependent on the water-to-binder weight ratio (w/b). This dependency was closely related to the formation of calcium oxychloride, which generally causes severe expansive cracking and depends on w/b.

The single use of CaO has been regarded as relatively unsuccessful in fly ash activation when no other additives are used together, as it produces a considerably lower strength compared to other types of activators (e.g., alkaline activators). This study investigated two potential additives of nitrate compounds (i.e., Ca(NO3)2 and NaNO3) to improve the strength of a CaO-activated fly ash system. The results showed that the use of Ca(NO3)2 was greatly beneficial in the strength improvement of the binder system primarily due to the significant increase in (1) the dissolution degree of fly ash, (2) C–S–H formation, and (3) pore size refinement from early days; however, NaNO3 was much less advantageous in strength improvement, although it also aided in dissolving fly ash.

This study explored the possibility of using reverse osmosis (RO) reject water as a mixing water for producing cementitious bricks using calcium sulfoaluminate (CSA) cement along with gypsum, and it investigated the changes in the properties of CSA cement pastes when RO reject water was used. The results were compared with those obtained using purified water and seawater. Overall, the use of RO reject water improved the cement paste&rsquo, s strength. Given that the use of RO reject water very slightly affected ettringite formation but more significantly influenced the Al2O3-Fe2O3-mono (AFm) phases (i.e., monosulfate, kuzelite, and Friedel&rsquo, s salt) and amorphous aluminum hydroxide (AH3), the strength improvement was likely mainly due to the formation of Friedel&rsquo, s salt rather than ettringite formation. This study also demonstrated that the use of RO reject water for brick production satisfied the Korean Standards (KS) F 4004 and toxicity characteristic leaching procedure (TCLP), thus, it is recommended to use RO reject water as a mixing water to produce CSA cement bricks for use in construction.

Significant variations have been reported on the temperature range of thermal decomposition of cementitious phases. Thus, this study identified temperature ranges on the phases in actual cementitious systems (portland cement (OPC) pastes, blended pastes of ground granulated blast furnace slag (GGBFS) with OPC, and Ca(OH)2-activated GGBFS) by simultaneously using thermogravimetry (TG) and high-temperature X-ray diffraction (HT-XRD) as follows: (1) 81°–91 °C for dehydration of ettringite, (2) ∼80°–240 °C for major dehydration of C-S-H, (3) ∼241°–244 °C for hydrogarnet, (4) ∼129°–138 °C for Al2O3-Fe2O3-mono phase (AFm), (5) ∼411°–427 °C for Ca(OH)2, and (6) ∼648°–691 °C for CaCO3. The CaO layers and SiO2 chains of C-S-H likely started to decompose from 615°–630 °C, and eventually transformed to new crystalline phases. This study also demonstrated that (a) the quantity of calcite could be overestimated due to additional carbonation when Ca(OH)2 is plentifully present in samples, and (b) the quantification of phases would be greatly affected by sample particle size when GGBFS is used in the system.

This study investigated frequency-difference electrical resistance tomography (ERT) using a 16-channel ERT system to detect rebar embedded in cement mortar. Two different data collecting methods (i.e., reference-difference and frequency-difference) were used for ERT image reconstruction, and the reconstructed ERT images were validated with binarized micro-CT images. As a result, the reference-difference ERT was not suitable for detecting rebar in cement mortar. This method generated incorrect ERT reconstruction images since the target specimen and reference specimen is different, and thus an inconsistent contact impedance, electrode position error, and different pore distributions between the samples could generate measurement errors affecting internal conductivity distribution. However, use of the frequency-difference method provided more accurate and reliable results for detecting rebar. The ERT images were well-matched with the binarized micro-CT images. In frequency-difference ERT, an identical specimen is used to obtain measurement data, and thus the experimental errors can be largely reduced. In particular, the reconstruction result was influenced by the range of the two used frequencies. In wide-ranging frequency-difference ERT, the rebar was better tracked regardless of distance from the electrodes than when using a narrow range of frequencies.

This study explores the use of precipitated calcium carbonate (PCC), an industrial by-product from the carbon sequestration process for emitted CO2 from factories, in the cementless CaO-activated ground-granulated blast-furnace slag (GGBFS) system in an aim not only to improve the strength but also to develop more sustainable structural binder for concrete. The 28-day strength improved with increasing PCC content up to 20 wt%, and its highest strength showed an ∼23% increase from the original strength of the sample without PCC. The analysis revealed that the PCC was not a simple inert filler, but it might promote more dissolution of GGBFS, resulting in a higher strength from additional formation of reaction products. In particular, even the sample with 50 wt% PCC yielded a very similar strength compared to the sample without PCC at 28 days. Thus, this binder system could be a decent solution that can store a large amount of PCC without a significant strength reduction.

This study presented CaCl 2 as a potential additive activator to develop a new strong, price-competitive CaO-activated GGBFS binder blended with fly ash (CAS 4:4:2) to commercially replace ternary blended cements, which generally consist of 40% Portland cement, 40% GGBFS, and 20% fly ash (wt.%) (PC 4:4:2), widely used for concrete production. Despite CAS 4:4:2 having no clinker cement compound, the addition of CaCl 2 not only significantly accelerated reactions of CAS 4:4:2 binders but also largely increased strengths at all curing days. Up to 72 h, the cumulative reaction heat of CAS 4:4:2 with CaCl 2 was also reasonably low. Reaction products and microstructures of hardened CAS 4:4:2 pastes were considerably changed after CaCl 2 addition. The CaCl 2 presence markedly promoted dissolution of the glass phase of GGBFS and fly ash in early days, resulting in more production of reaction products (e.g., C-S-H, hydrocalumite) and pore-size refinement.

This study explored the influence of using copper slag as an alternative sand for producing cement mortar bricks and its effect on γ-ray attenuation property, strength, and consistency of mortar. The linear attenuation coefficients and mass attenuation coefficients were experimentally determined for mortar mixtures using the 60Co and 137Cs gamma-ray source, and, using the Phy-X program, attenuation parameters were theoretically calculated in 1 keV–100 GeV. Sample bricks with added copper slag were produced and tested. In the results, the added copper slag was greatly beneficial for increasing the flowability and strength of mortar, and, given all the results of attenuation parameters, the use of copper slag as aggregates was notably advantageous compared to silica sands for gamma-ray attenuation mainly due to the high Fe quantity in copper slag. The trial brick specimens using 100 wt% copper slag replacement for sand not only satisfied all requirements of cement brick in the Korean standard (KS) F 4004, but also the TCLP regulation.

This study investigated the role of crystallinity of added nanometer-sized Al2O3 (nano-alumina) (i.e., poorly crystalline nano-alumina (γ-alumina) vs. crystalline nano-alumina (α-alumina)) and the interaction of nano-aluminas with added gypsum in the CaO-activated ground granulated blast furnace slag (GGBFS) binder system. In the results, the use of γ-alumina evidently increased the dissolution degree of silicon (Si) from GGBFS regardless of adding gypsum, which was the main ingredient of calcium silicate hydrate (C-S-H), and thus led to a noticeable increase of C-S-H. However, the sole use of α-alumina without added gypsum barely affected the C-S-H formation, although the added α-alumina alongside gypsum also had a similar effect on the dissolution of Si. In addition, due to the amorphous nature of γ-alumina, the dissolution of γ-alumina was faster than that of α-alumina. Thus, the use of γ-alumina produced ettringite at the faster rate, as well achieving the greater and faster strength increase, although the added α-alumina was also slightly beneficial in accelerating the formation of ettringite. Thus, overall, the use of γ-alumina was significantly more advantageous in improving strength by increasing the quantities of reaction products (C-S-H and/or ettringite) than that of α-alumina.

Reducing the specific gravity (SG) of structural binder pastes is one possible way to prevent material segregation between binder paste and lightweight aggregates, which often occurs in producing lightweight concrete due to their SG differences. To this end, this study suggests the use of a new lightweight fly ash binder paste, given that its SG can largely be reduced simply by increasing the water-to-binder (w/b) ratio without both excessive bleeding and significant strength reduction. Class F fly ash was activated with varying weights of water (i.e., w/b), Ca(OH) 2 , and Na 2 CO 3 to prepare the samples. Compressive strength, SG, and water absorption were measured with microstructural study using XRD, TG, and MIP. The results showed satisfactory performances with strengths of 27.8–56.5 MPa, an oven-dried SG of 1.24–1.47, and water absorption of 13.3–24 wt% for selected representative mixtures at 28 days. In particular, the strongest sample, at 56.5 MPa, also obtained a low value of oven-dried SG of 1.47, which lay within the range of oven dried SG (∼ 0.6–1.5) of commercial lightweight aggregates. In this study, strength, SG, water absorption, reaction products, and pore characteristics were mainly determined by w/b ratio rather than Ca(OH) 2 and Na 2 CO 3 contents; thus, this binder would be more advantageous for quality control than other types of fly ash-based cementless binders in structural construction.

This paper explored the effectiveness of red mud and a mixture powder of Ca(OH) 2 ( C), Na 2 CO 3 ( N), and fly ash ( F) (denoted CNF powder) as precursor materials to produce an environment-friendly high strength brick product. Overall, despite the inclusion of up to ∼81% of red mud and fly ash, 7-day strengths were developed ∼17–34 MPa; this was high enough to be used as a structural binder for brick production. In particular, the use of NaOH was very effective in increasing flowability, and, more importantly, early strength in the red mud-CNF blended system, despite the red mud inclusion, because NaOH greatly improved the degree of reaction of the system, resulting in more calcium silicate hydrates (C-S-H) formation as well as significant pore size refinement at early days of curing. Trial bricks were also prepared to examine possible toxicity due to the inclusion of red mud and fly ash using the toxicity characteristic leaching procedure (TCLP) test and the TCLP concentrations were very low.

In this study, barium hydroxide was proposed as a main activator for ground granulated blast-furnace slag (GGBFS) to produce a strong binder, and it was compared to calcium hydroxide in terms of strength development, reaction products, and microstructure. The Ba(OH)2-activated GGBFS (BHAS) achieved a significantly higher compressive strength than Ca(OH)2-activated GGBFS (CHAS), except at 3 days, mainly due to (1) the more formation of hydration products, leading to a notable reduction in pore sizes and volume, and (2) the higher solubility of Ba(OH)2, resulting in a higher dissolution of GGBFS than that of Ca(OH)2. Although calcium silicate hydrate (C-S-H) was a major reaction product in both mixtures, the Ca/Si ratios were much different. In the BHAS, the presence of barium ions prohibited the synthesis of ettringite and monocarboaluminate, which formed in the CHAS mixtures, but it induced Ba-bearing products, stratlingite, and the hydrotalcite-like phase. The removal of ettringite was the cause of the lower strength of the BHAS at 3 days compared to that of the CHAS.

Sulfur polymer concrete (SPC) is a thermoplastic composite that is generally composed of modified sulfur polymer binder and aggregate. This study proposed a new approach for developing sustainable sulfur composites by using only hazardous industrial wastes without aggregate. The industrial wastes used in this study were sulfur, fly ash, and rubber powder from waste tires. The proposed method may have several major advantages compared to using cement-based concrete as well as traditional SPC: less CO2 emissions, lower life-cycle cost, and superior durability. To examine the effects of waste rubber powder and fly ash on the strength and microstructure of sulfur composites after three days of curing, a series of characterization analyses were conducted based on the tests of compressive strength, powder X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and mercury intrusion porosimetry. The test results suggested that the replacement of sulfur with fly ash up to about 45% generally improved the compressive strength of sulfur composites, and rubber powder effectively substituted fine aggregate or a portion of sulfur without significant strength reduction. This study also revealed that the microstructure of sulfur composites was significantly affected by varying the amounts of fly ash or rubber powder, despite no change in reaction products.