Characteristic Analysis and Risk Control of Syngas Explosion during Underground Coal Gasification.

Gas explosion is one of the main accident risks during underground coal gasification (UCG). There are significant differences in the gas composition and explosive environment between UCG syngas and other gases. Previous research on the explosion characteristics of UCG syngas is not comprehensive enough, especially without considering the influence of the initial temperature on various characteristic parameters. A set of calculation methods for explosion characteristic parameters of UCG syngas based on existing research was proposed, which was applied to analyze explosion characteristics of syngas produced by different gasifying processes in the Huating UCG industrial test. The results showed that with the initial temperature improving, the maximum temperature and upper explosion limit of different gases increased, while the maximum pressure, lower explosion limit, and oxygen content safety limit decreased. However, the explosion thermal effect, pressure rise rate, and explosion characteristic values showed small changes. When the initial temperature increased from 298 to 1473 K, the explosion temperature of different gas explosions increased from 1645-2286 to 2652-3238 K, the maximum pressure dropped from 0.59-0.81 MPa (absolute pressure) to 0.19-0.23 MPa, the lower explosion limit dropped from 12.34-29.79% to 0.58-1.77%, the upper explosion limit increased from 55.68-83.35% to 70.89-93.73%, and the safety limit of oxygen content dropped from 4.86-6.37% to 0.26-0.34%. In addition, the gas calorific value also affected the values of various explosion characteristic parameters, among which the explosive thermal effect, maximum temperature, maximum pressure, pressure rise rate, explosion characteristic value, and safety limit of oxygen content in the syngas were all proportional to the calorific value of gas, while the lower and upper limits of explosion were inversely proportional to it. Based on the above research, syngas explosion-prone stages and causes of each potential risk area in the Huating UCG project were analyzed, the explosion characteristic parameters were determined, and targeted prevention and control measures were proposed accordingly. This study can lay a theoretical foundation for the study of syngas explosion characteristics and risk control for the UCG project.

Interfacial alloying between lead halide perovskite crystals and hybrid glasses.

The stellar optoelectronic properties of metal halide perovskites provide enormous promise for next-generation optical devices with excellent conversion efficiencies and lower manufacturing costs. However, there is a long-standing ambiguity as to whether the perovskite surface/interface (e.g. structure, charge transfer or source of off-target recombination) or bulk properties are the more determining factor in device performance. Here we fabricate an array of CsPbI3 crystal and hybrid glass composites by sintering and globally visualise the property-performance landscape. Our findings reveal that the interface is the primary determinant of the crystal phases, optoelectronic quality, and stability of CsPbI3. In particular, the presence of a diffusion "alloying" layer is discovered to be critical for passivating surface traps, and beneficially altering the energy landscape of crystal phases. However, high-temperature sintering results in the promotion of a non-stoichiometric perovskite and excess traps at the interface, despite the short-range structure of halide is retained within the alloying layer. By shedding light on functional hetero-interfaces, our research offers the key factors for engineering high-performance perovskite devices.

Recent advances in enzymatic biofuel cells enabled by innovative materials and techniques.

The past few decades have seen increasingly rapid advances in the field of sustainable energy technologies. As a new bio- and eco-friendly energy source, enzymatic biofuel cells (EBFCs) have garnered significant research interest due to their capacity to power implantable bioelectronics, portable devices, and biosensors by utilizing biomass as fuel under mild circumstances. Nonetheless, numerous obstacles impeded the commercialization of EBFCs, including their relatively modest power output and poor long-term stability of enzymes. To depict the current progress of EBFC and address the challenges it faces, this review traces back the evolution of EBFC and focuses on contemporary advances such as newly emerged multi or single enzyme systems, various porous framework-enzyme composites techniques, and innovative applications. Besides emphasizing current achievements in this field, from our perspective part we also introduced novel electrode and cell design for highly effective EBFC fabrication. We believe this review will assist readers in comprehending the basic research and applications of EBFCs as well as potentially spark interdisciplinary collaboration for addressing the pressing issues in this field.

Prediction of rock burst intensity based on multi-source evidence weight and error-eliminating theory.

Rock burst is the main geological hazard in deep underground engineering. For the prediction of the intensity of rock burst, a model for prediction of rock burst intensity on the basis of multi-source evidence weight and error-eliminating theory was established. Four indexes including the ratio of rock's compressive-tensile strength [Formula: see text], the stress coefficient of rock [Formula: see text], the elastic energy index of rock Wet, and integrality coefficient Kv were chosen as the prediction variables of rock burst; the index weights are calculated by different weighting methods and fused with evidence theory to determine the final weight of each index. According to the theory of error-eliminating, taking "no rock burst" (I in classification standards of rock burst intensity) as the objective and using the error function to process 18 sets of typical rock burst data and the weight of evidence fusion as the normalized index limit loss value, a model for prediction of rock burst intensity was built. It is verified by the actual situation and three other models. Finally, the model has been applied to rock burst prediction of Zhongnanshan tunnel ventilation shaft. The results show that evidence theory fuses multi-source index weights and improves the method of determining index weights. The index value is processed by error-eliminating theory, and the limit value problem of index value normalization is optimized. The predicted results of the proposed model are consistent with the situation of Zhongnanshan tunnel. It improves the objectivity of the rock burst prediction process and provides a research idea for rock burst intensity prediction index.

Modeling Methodology for Site Selection Evaluation of Underground Coal Gasification Based on Combination Weighting Method with Game Theory.

The lack of systematic geological work is an essential reason why underground coal gasification (UCG) has not been industrialized for a long time. Building a scientific index system and favorable area evaluation technology for the UCG site selection is the key to breaking through the geological bottleneck. Aiming at the problems of the single index weight determination method, intense subjectivity, and poor reliability of current evaluation models, we put forward an evaluation modeling methodology for the UCG site selection using the combination weighting method with the game theory. The factors of coal resource conditions associated with the potential risk of UCG are systematically analyzed. From the six dimensions of the geological structure, hydrogeology, seam occurrence, coal properties, reserves, and roof lithology, 23 key factors were selected as evaluation indexes to construct a hierarchical model composed of the target layer, category index layer, and index layer. The influence of each index on UCG and its reasonable value range were systematically analyzed. The evaluation index system for UCG site selection was formed. The improved analytic hierarchy process (AHP) was adopted to sequence indices and determine their subjective weight. And the variability, conflict, and information amount of the index data were analyzed by the CRiteria Importance Through Intercriteria Correlation (CRITIC) method to calculate the objective weight. Then, the subjective and objective weights were combined through game theory. On this basis, fuzzy theory was employed to calculate the membership of indices and construct the fuzzy comprehensive judgment matrix. The evaluation model of the UCG site selection was applied to the suitability evaluation of resource conditions of UCG pilot projects at Zhongliangshan (ZLS), Huating (HT), and Shanjiaoshu (SJS) mines in China. The result shows that the resource conditions of HT are the best, followed by ZLS and, finally, SJS, which are consistent with the actual running effects of the three UCG pilot projects. It indicates that the evaluation model can provide a scientific theoretical basis and reliable technical support for the UCG site selection.

Binder-free mechanochemical metal-organic framework nanocrystal coatings.

The practical applications of metal-organic frameworks (MOFs) usually require their assembly into mechanically robust structures, usually achieved via coating onto various types of substrates. This paper describes a simple, scalable, and versatile mechanochemical technique for producing MOF nanocrystal coatings on various non-prefunctionalised substrates, including ZrO2, carbon cloth, porous polymer, nickel foam, titanium foil and fluorine-doped tin oxide glass. We revealed the detailed mechanisms that ensure the coating's stability, and identified the coating can facilitate the interfacial energy transfer, which allowed the electrocatalysis application of the MOF coating on conductive substrates. We further demonstrated that coatings can be directly generated in a one-pot fashion by ball milling MOF precursors with substrates.

[Effectiveness of volar oblique T-type locking plate and raft screws reduction and fixation in treatment of extreme distal radius fractures].

OBJECTIVE: To investigate the effectiveness of volar oblique T-type locking plate and raft screws reduction and fixation in the treatment of extreme distal radius fractures. METHODS: Between July 2014 and July 2018, 15 patients with extreme distal radius fractures were treated with volar oblique T-type locking plate and raft screws reduction and fixation. There were 6 males and 9 females, aged from 30 to 66 years with an average age of 56.6 years. The cause of injury was falling from height in 2 cases and falling in 13 cases. All of them were fresh closed injuries. The fractures were rated as type 23C1 in 8 cases and as type 23C2 in 7 cases according to AO/Orthopaedic Trauma Association (AO/OTA) classification. There were 7 cases of ulnar styloid process fracture and 2 cases of distal radioulnar joint instability. The time from injury to operation was 6 to 9 days with an average of 7.3 days. The fracture healing and the radial height, palm inclination, and ulnar deviation were observed by X-ray reexamination. Cooney score was used to evaluate the effectiveness. RESULTS: All incisions healed by first intention. All patients were followed up 12-24 months, with an average of 14.6 months. X-ray films showed that all fractures healed, and the healing time ranged from 5 to 10 months, with an average of 8.2 months. No internal fixation failure or secondary fracture displacement occurred. At last follow-up, the radial height, palm inclination, and ulnar deviation recovered well, and the differences between pre- and post-operation were significant ( P<0.05). The pain, function, activity, and grip strength scores and the total score of Cooney score were significantly higher than those before operation ( P<0.05). There were 11 cases of excellent, 3 cases of good, and 1 case of good, with an excellent and good rate of 93%. CONCLUSION: For extreme distal radius fractures, the volar oblique T-type locking plate and raft screws reduction and fixation can restore the radialheight, palm inclination, and ulnar deviation, fix firmly, and recover the wrist joint function exercise early, and obtain satisfactory effectiveness.

[Effectiveness analysis of closed or limited open reduction and intramedullary nail fixation in treatment of Seinsheimer type â ¤ subtrochanteric fracture].

OBJECTIVE: To investigate the effectiveness of closed or limited open reduction and intramedullary nail fixation in the treatment of Seinsheimer type Ⅴ subtrochanteric fracture. METHODS: Between May 2014 and July 2018, 36 patients with Scinsheimer type Ⅴ subtrochanteric fractures were treated with closed or limited open reduction and intramedullary nail fixation. There were 25 males and 11 females with an age of 23-86 years (mean, 55.8 years). The cause of injury included falling in 19 cases, traffic accident in 9 cases, falling from height in 7 cases, and heavy object injury in 1 case; all were fresh closed injuries. The interval between injury and operation was 1-14 days (mean, 6.8 days). There were 18 cases of closed reduction and 18 cases of limited open reduction during the operation. Seventeen cases were fixed with femoral reconstruction intramedullary nail, 5 with InterTan long nail, 14 with lengthened proximal femoral nail anti-rotation, and 7 cases were assisted with auxiliary steel wire binding. After operation, through X-ray film and clinical follow-up, the fracture reduction and maintenance status, internal fixation position, and fracture healing were judged; the range of motion, walking ability, and complications of hip joint were observed, and the function of hip joint was evaluated according to Merle d'Aubigne Postel hip joint scoring standard. RESULTS: All the incisions of medullary operation healed by first intention, and no vascular, nerve injury, or infection occurred. All patients were followed up 12-24 months, with an average of 14.2 months. Among the 36 patients, 1 patient received revision surgery due to varus displacement of femoral head and screw penetration at 2 months after closed reduction, with poor recovery of hip function. X-ray film re-examination showed that the fractures of the other 35 patients healed after 9-15 months, with an average of 11.5 months. During follow-up, there was no complication such as internal fixation failure, fracture redisplacement, bone nonunion or malunion, and deep vein thrombosis of lower extremity occurred. The function of hip joint recovered well, and the patients could walk and squat normally without affecting daily life or work. At last follow-up, according to Merle d'Aubigne Postel hip joint scoring standard, 28 cases were rated as excellent, 4 cases as good, 3 cases as fair, and 1 case as poor, the excellent and good rate was 88.9%. CONCLUSION: C-arm X-ray fluoroscopic closed or limited open reduction and intramedullary nail fixation for the treatment of Seinheimer Ⅴ type subtrochanteric fracture, if necessary, with the aid of auxiliary steel wire binding, it has the advantages of less blood supply destruction at the fracture end, satisfactory reduction, firm fixation, and early rehabilitation training, with definite effectiveness.

[Open reduction and internal fixation for multiple injuries of superior shoulder suspensory complex with coracoid process fracture].

OBJECTIVE: To investigate the effectiveness of open reduction and internal fixation for multiple injuries of superior shoulder suspensory complex (SSSC) with coracoid process fracture. METHODS: Between January 2014 and October 2018, 22 patients with multiple injuries of SSSC with coracoid process fracture were treated by open reduction and internal fixation. There were 16 males and 6 females, aged from 24 to 72 years with an average age of 36.6 years. There were 10 cases of falling injury, 5 cases of traffic accident injury, and 7 cases of falling from height injury. All of them were fresh closed injuries. The time from injury to operation ranged from 2 to 17 days with an average of 6.9 days. Both X-ray film and CT showed the coracoid process fracture complicated with clavicular fracture in 14 cases, acromioclavicular joint dislocation in 12 cases, and acromioclavicular fracture in 5 cases. There were 14 cases of two places of SSSC, 7 cases of three places of SSSC, and 1 case of four places of SSSC. RESULTS: All incisions healed in primary stage after operation. All patients were followed up 10-24 months with an average of 14.1 months. X-ray films showed that all fractures healed and the acromioclavicular joint was normal. The healing time ranged from 6 to 12 months, with an average of 6.2 months. No complications such as internal fixation failure and nonunion occurred. According to University of California Los Angeles (UCLA) shoulder scoring system, the shoulder joint function was rated as excellent in 15 cases, good in 5 cases, and poor in 2 cases at last follow-up. The excellent and good rate was 90.9%. CONCLUSION: Open reduction and internal fixation for treatment of multiple injuries of SSSC with coracoid process fracture is firm and reliable. Combined with active postoperative rehabilitation program intervention, it can accelerate the recovery of shoulder joint function and achieve satisfactory effectiveness.

A Novel, Hybrid-Integrated, High-Precision, Vacuum Microelectronic Accelerometer with Nano-Field Emission Tips.

In this paper, a novel, hybrid-integrated, high-precision, vacuum microelectronic accelerometer is put forward, based on the theory of field emission; the accelerometer consists of a sensitive structure and an ASIC interface (application-specific integrated circuit). The sensitive structure has a cathode cone tip array, a folded beam, an emitter electrode, and a feedback electrode. The sensor is fabricated on a double-sided polished (1 0 0) N-type silicon wafer; the tip array of the cathode is shaped by wet etching with HNA (HNO3, HF, and CH3COOH) and metalized by TiW/Au thin film. The structure of the sensor is finally released by the ICP (inductively coupled plasma) process. The ASIC interface was designed and fabricated based on the P-JFET (Positive-Junction Field Effect Transistor) high-voltage bipolar process. The accelerometer was tested through a static field rollover test, and the test results show that the hybrid-integrated vacuum microelectronic accelerometer has good performance, with a sensitivity of 3.081 V/g, the non-linearity is 0.84% in the measuring range of -1 g~1 g, the average noise spectrum density value is 36.7 µV/ Hz in the frequency range of 0⁻200 Hz, the resolution of the vacuum microelectronic accelerometer can reach 1.1 × 10-5 g, and the zero stability reaches 0.18 mg in 24 h.

A modified mini-incisional technique for double-eyelid blepharoplasty.

BACKGROUND: Double-eyelid blepharoplasty is one of the most popular cosmetic surgeries in Asia. OBJECTIVE: To introduce a modified mini-incisional technique to form a double eyelid. METHODS: A total of 372 patients (325 women, 47 men) were involved in the study between July 2008 and August 2014. Their age ranged from 16 to 34 years, with a mean age of 24 years. All patients underwent the modified mini-incisional upper blepharoplasty. In the technique, four 2 mm incisions were made along the designed fold. The orbicularis muscle overlying the levator aponeurosis was removed. The removal of the lateral fat pad was completed accordingly. The medial fat pad was also removed if necessary. Suture was used to fix the skin to pretarsal fascia along the double-eyelid line. The double-eyelid crease was formed after the operation. RESULTS: The follow-up period was three to 12 months (mean nine months). Most of the double eyelids were natural. During the follow-up period, 92% (342 of 372) patients were satisfied with the blepharoplasty. The most common complications were swelling within first week after the operation, which subsided spontaneously. Asymmetries occurred in 17 patients; six patients had multiple eyelids and seven patients experienced shifting of the fold. These were corrected six months after the operation. Disappearance of the fold was not observed. The scars of the stab incision became invisible after one full year of recovery. No other severe complications were found. CONCLUSION: The four mini-incisional blepharoplasty technique was successful for the formation of a natural-appearing and long-lasting double eyelid. Except for individuals with obvious skin redundancy, patients with a single eyelid are suitable candidates for the technique.

HISTORIQUE: La blépharoplastie asiatique est l'une des chirurgies plastiques les plus populaires en Asie. OBJECTIF: Présenter une technique de mini-incisions modifiée pour former un pli palpébral. MÉTHODOLOGIE: Au total, 372 patients (325 femmes, 47 hommes) ont participé à l'étude entre juillet 2008 et août 2014. Ils avaient de 16 à 34 ans, pour un âge moyen de 24 ans. Ils ont tous subi une blépharoplastie asiatique par mini-incisions modifiées. Les chirurgiens ont pratiqué quatre incisions de 2 mm le long du pli désigné. Ils ont effectué l'exérèse du muscle orbiculaire recouvrant l'aponévrose du muscle releveur et celle des tissus graisseux latéraux, puis ont procédé à celle des tissus médians, au besoin. Ils ont réalisé une suture pour fixer la peau au fascia prétarsal le long de la ligne du pli. Le pli palpébral a été formé après l'opération. RÉSULTATS: La période de suivi était de trois à 12 mois (moyenne de neuf mois). La plupart des plis palpébraux avaient un aspect naturel. Pendant la période de suivi, 92 % des patients (342 sur 372) étaient satisfaits de la blépharoplastie. Les principales complications étaient une enflure pendant la première semaine suivant l'opération, qui s'est résorbée spontanément. Dix-sept patients ont présenté une asymétrie; six patients avaient de multiples plis et sept patients ont présenté un déplacement du pli, qui a été corrigé six mois après l'opération. Aucun pli n'a disparu. Après une année complète de convalescence, les cicatrices des incisions étaient devenues invisibles. Aucune autre grave complication n'a été observée. CONCLUSION: La technique de blépharoplastie par quatre mini-incisions permet de former un pli palpébral supérieur d'aspect naturel à long terme. À part chez les personnes qui présentent une redondance cutanée évidente, les patients qui ont des paupières asiatiques sont de bons candidats à cette intervention.

The application of temporo-occipital fascial flap in the wound of medium scalp defect with bone exposure.

We are aimed to observe the effect of applying the combined temporo-occipital fascial flap in the medium scalp defect with bone exposure. Three cases of moderate scalp defect with bone exposure were admitted by The 89th Hospital of PLA and China-Japan Friendship Hospital from October 2009 to March 2014, and the wounds were repaired by application of the temporo-occipital fascial flap with medium-thickness skin grafting. And then these 3 patients were followed up after the operation, and the wound repair was observed. These 3 cases of fascial flaps all survived well with good appearance and covered the wound completely. Fibrosarcoma of one case had a relapse 3 months after operation, and the other two cases were followed up from 6 months to 3 years. Meanwhile, the appearance and function were satisfactory. The communicating branches between superficial temporal artery and occipital artery are rich. Therefore we designed and utilized the long temporo-occipital fascial flap containing the ipsilateral occipital superficial fascia to repair the scalp defect with bone exposure, and the curative effect is satisfactory.

Distally based dorsal pedal neurocutaneous flap for forefoot coverage.

The authors describe their experience with the use of the distally based dorsal pedal neurocutaneous flap for distal foot coverage. Ten patients underwent reconstruction with 13 flaps between 2004 and 2008. One patient suffered from a traffic accident and 9 from electrical injury. All of the soft tissue defects resulted in metatarsophalangeal joint and phalanx bone exposure. The size of the flaps ranged from 6 × 2 cm to 11 × 6 cm. The flaps were elevated based on intermediate or medial dorsal pedal nerves. Nine flaps were harvested in first stage to repair the distal foot. Among them, 3 showed partial necrosis in the distal region because of venous insufficiency. Four flaps underwent a surgical delay procedure in the first stage and were then transferred to reconstruct phalanx wounds in the second stage, surviving completely. All patients were satisfied with their reconstruction and donor site contour. The distally based dorsal pedal neurocutaneous flap can be used to repair the distal foot soft tissue defects, providing sufficient skin territory and excellent aesthetic and functional recovery. Surgical delay effectively enhances the distally based dorsal pedal neurocutaneous flap survival, particularly for the large size flaps.