Dual Zone Research Articles

Preservation of Socket for Immediate Dental Implants in Aesthetic Zone from Upper Jaw: Aesthetic Approach-Case Report

Ensuring optimal aesthetic outcomes in dental implant cases within the maxillary anterior area requires careful consideration of socket preservation and atraumatic tooth extraction. These factors play a crucial role in achieving successful and aesthetically pleasing treatments. The objective of this study is to present a series of clinical cases involving dental extractions of anterior maxillary teeth with a poor prognosis. This study highlights the importance of socket preservation and atraumatic tooth extraction in ensuring optimal aesthetic results in dental implant cases within the maxillary anterior area. In these cases, a two-armed lever technique was planned for atraumatic alveolar preservation during the extraction process.Following the tooth extraction, the fresh socket was reclassified, and dental implants were subsequently placed using a modified drilling technique in certain cases. The authors assessed the primary stability of the implants, while in other cases, bone regeneration procedures were performed. The presented clinical cases demonstrate the successful implementation of the two-armed lever technique for atraumatic alveolar preservation, leading to favorable outcomes in terms of primary implant stability and bone preservation. Techniques for bone preservation after tooth extraction aim to minimize post-extraction bone resorption. By implementing appropriate protocols, such as the concept of the dual zone and the two-armed lever technique, successful outcomes can be achieved in terms of both aesthetics and preservation of the alveolar bone.

The bone shielding versus dual-zone concept in treating thin-walled fresh extraction sockets with immediate implant placement: Soft and hard tissue changes. A randomized clinical trial.

To evaluate the ridge alterations and esthetic outcome 1 year after immediate implant placement using the dual-zone (DZ) technique versus the bone shielding concept in patients with intact thin-walled sockets in the esthetic zone. This randomized clinical trial included 26 patients with nonrestorable maxillary teeth in the esthetic zone who were randomly assigned to two groups (n = 13 each) to receive immediate implants using either the bone shielding concept or DZ. Definitive restorations were delivered after 2 months. Pink esthetic scores (PESs), vertical soft tissue alterations, and bucco-palatal ridge dimensional changes were measured and assessed using intra-oral digital scans at baseline and 1 year post-procedure. Labial bone thickness was measured using cone beam computed tomography scans at baseline and after 1 year. The bone shielding group provided bucco-palatal ridge thickness stability after 1 year (9.43 mm) compared to baseline values (9.82 mm), while DZ showed a significant loss in the bucco-palatal ridge thickness after 1 year (7.83) compared to baseline values (9.49). No significant difference was reported in the baseline bucco-palatal ridge thickness between the two groups (p = 0.6). After 1 year, the bone shielding group demonstrated 0.38 mm ridge shrinkage which was statistically significant (p = 0.0002) compared to 1.67 mm ridge shrinkage in the DZ group. In addition, the average total PES in the bone shielding group was 12.04 versus 10.28 in the DZ group. No significant difference was reported in the mesial papilla length between the DZ and the bone shielding group after 1 year (p > 0.05). However, the midfacial gingival margin (p = 0.026) and distal papilla were significantly higher in the DZ group (p = 0.0025). There was no significant difference in the mean ± SD mm bone gain at the apical level between the two studied groups after 1 year (p = 0.06) showing 0.85 ± 0.23 and 0.64 ± 0.32 mm, respectively. However, the bone shielding concept showed a statistically significant more bone gain mm (p < 0.001) at the (0.56 ± 0.43) and crestal (0.03 ± 0.8) levels after 1 year compared to DZ which revealed 0.18 ± 0.5 and 0.38 ± 0.29 mm bone loss, respectively. The bone shielding concept might offer a reliable alternative for restoring thin-walled sockets by minimizing postextraction ridge dimensional alterations effect following immediate implant placement in the esthetic zone. Nevertheless, the study suffers from confounding bias since there are two systematic differences between the groups, the barrier membrane type, and the level of bone filling. "This clinical trial was not registered prior to participant recruitment and randomization." NCT05381467.

TRANSLATION OF MATERIAL MODELS FOR BONE FRACTURE CALLUS FROM PRECLINICAL TO CLINICAL APPLICATIONS

Virtual mechanical testing is a method for measuring bone healing using finite element models built from computed tomography (CT) scans. Previously, we validated a dual-zone material model for ovine fracture callus that differentiates between mineralized woven bone and soft tissue based on radiodensity.1 The objective of this study was to translate the dual-zone material model from sheep to two important clinical scenarios: human tibial fractures in early-stage healing and late-stage nonunions.CT scans for N = 19 tibial shaft fractures were obtained prospectively at 12 weeks post-op. A second group of N = 33 tibial nonunions with CT scans were retrospectively identified. The modeling techniques were based on our published method.2 The dual-zone material model was implemented for humans by performing a cutoff sweep for both the 12-week and nonunion groups. Virtual torsional rigidity (VTR) was calculated as VTR = ML/φ [N-m2/°], where M is the moment reaction, L is the diaphyseal segment length, and φ is the angle of twist.As the soft tissue cutoff was increased, the rigidity of the clinical fractures decreased and soft tissue located within the fracture gaps produced higher strains that are not predicted without the dual zone approach. The structural integrity of the nonunions varied, ranging from very low rigidities in atrophic cases to very high rigidities in highly calcified hypertrophic cases, even with dual-zone material modeling.Human fracture calluses are heterogeneous, comprising of woven bone and interstitial soft tissue. Use of a dual-zone callus material model may be instrumental in identifying delayed unions during early healing when callus formation is minimal and/or predominantly fibrous with little mineralization.ACKNOWLEDGEMENTS:This work was supported by the National Science Foundation (NSF) grant CMMI-1943287.

A new concept for high efficiency and clean diesel combustion by controlling mixture distribution with dual zone combustion chamber

While various measures are being promoted globally toward carbon-neutrality, internal combustion engines are required to achieve a further improvement in thermal efficiency in order to generate less CO2. For diesel engines, premixed charge compression ignition (PCI) combustion has been proposed as a combustion method that can achieve high thermal efficiency and clean emissions simultaneously. However, the application of PCI combustion remains limited to the light load range of certain mass-produced engines as it is difficult to control ignition timing and combustion noise. In this study, we developed a new combustion concept, Distribution Controlled partially Premixed Compression Ignition (DCPCI), which enables partially premixed combustion in medium load ranges by spatially controlling fuel mixture distribution. With this DCPCI combustion, we aim for highly efficient and clean combustion by suppressing the interference between the burned gas produced by the earlier stage injection and the subsequent spray with the use of a dual-zone combustion chamber and multi-stage injection. The effectiveness of the new combustion concept was validated by Computational Fluid Dynamics (CFD) analyses, and the improvement in thermal efficiency was confirmed by engine experiments.

Comparing Dual-Zone Immediate Implant Placement and Socket Shield Technique for Ridge Width Changes in the Maxilla: A Prospective Cohort Study.

The aim of this prospective cohort study was to assess the facial-palatal ridge dimensional changes that occurred at 8-10 months following flapless dual-zone (DZ) immediate implant placement and socket-shield (SS) immediate placement in the maxilla. A total of 19 patients who received 20 implants were included, with 10 implants (MegaGen AnyRidge) placed for each treatment, DZ and SS. Cast models were made at 8-10 months after implant placement to assess the dimensional ridge changes by measuring the facial-palatal ridge width on implant sites (T) at six designated points starting from the gingival margin (0, 1, 2, 3, 5 and 7) and comparing it with the corresponding measurement on the contralateral tooth site (C). All 20 implants demonstrated successful osseointegration at 8-10 months follow-up (survival rate 100%). Two out of ten cases of SS group presented with minor manageable complications of external shield exposure. DZ group showed an average of 0.3 mm facial-palatal ridge width reduction, while SS group revealed a mean gain in ridge width of approximately 0.2 mm at 8-10 months follow-up. When comparing between two treatments, there was a significant difference in ridge width change at 8-10 months following implant placement, indicating better preservation of the ridge contour for socket shield technique.

Numerical assessment of a solar pond under transient state with realistic energy extraction from all possible zones

A solar pond from which thermal energy is extracted from its non-convective zone (NCZ), lower convective zone (LCZ) and the ground below is modelled in transient state. The novelty of the study lies in the fact that heat extraction in each of the three zones is considered to be realistic, taking into account temperature drop across the exchanger surfaces. The pertinent weather parameters are described by curve fitting as series of sinusoidal time functions. Using these expressions, implicit finite difference method is used to solve the five coupled partial differential equations involved in the analysis, and the scaled down model is validated with simpler models available in the literature. To quantify the practical utility of pond, the final outgoing water stream heated from the pond is fed to a large scale solar still to assess the usefulness in a desalination application. Annual distillate production of the still coupled to such a pond is calculated and its variation with various manually adjustable parameters is studied. A total of 9 such parameters have been investigated. It is observed that there are five pond parameters related to pond’s operation that possess optimum values that maximize annual distillate production. These are: NCZ and LCZ thicknesses, NCZ and LCZ exchanger pipes’ radii, and ground extraction mass flow rate. An increase in any of the remaining parameters: upper convective zone (UCZ) thickness, ground exchanger pipes’ radius and NCZ, LCZ extraction mass flow rates generate a decrease in distillate produced. It is also revealed that extraction should be carried from how many zones depends on the application coupled to the pond, and in this case, where the application is a solar still, LCZ with ground extraction turns out to be the best choice. Further, the assumption of ideal NCZ and ground extraction used in the literature is seen to overestimate system output by nearly 46%. Therefore, this model is a generalized one and various other single or dual zone extraction models available so far become subsets of it. This generalized model presented here can serve to design such a triple zone extraction based solar pond system in a realistic and practical manner and help evaluate suitable values of user-controlled variables that yield maximum output of the application to which the pond supplies energy.

Clinical evaluation of the buccal aspect around immediate implant using dual zone therapeutic concept versus buccal gap fill to bone level: A randomized controlled clinical trial.

Soft tissue esthetics for immediate implant is considered challenging when restoring a tooth in an esthetic zone. This study aimed to evaluate the buccal aspect after immediate implant using the dual-zone therapeutic concept compared to grafting the buccal gap to the bone crest. Twenty-four patients were randomly assigned into either immediate implant with the dual-zone therapeutic concept (DZ, test group) or with bone grafting till buccal bone crest with immediate temporization (BCG, control group). Pink esthetic score (PES), buccal bone loss (BBL), mid-facial recession (MFR), soft tissue thickness (STT), keratinized tissue width (KTW), post-operative swelling (POS), and patient satisfaction (PS) were evaluated for 1year. At 12 months the PES in the test group was 11.36 ± 1.69, and 10.80 ± 1.55 in the control group, with no statistically significant difference (p= 0.45). MFR in the DZ and BCG groups was 0.27 ± 0.34 and 0.45 ± 0.44 after 12 months with no statistical significance difference (p= 0.195). The STT assessment showed a statistically significant increase in both groups, however the intergroup comparison was statistically not significant (p= 0.23). The mean KTW in the DZ and BCG groups was 4.55 ± 1.08 and 4.20 ± 0.82 mm, respectively with no statistical significance (p= 0.42). There was no statistical significant difference in patient satisfaction between the two groups except in question number 10 concerning the post-operative swelling which was higher in the DZ group (p= 0.009). Both treatment modalities are considered reliable methods to achieve good soft tissue esthetics. However, both treatment modalities were not effective in preventing facial bone resorption despite the use of bone graft.

A New Concept for High Efficiency and Clean Diesel Combustion by Controlling Mixture Distribution with Dual Zone Combustion Chamber

A New Concept for High Efficiency and Clean Diesel Combustion by Controlling Mixture Distribution with Dual Zone Combustion Chamber

Surface topography and enhanced photo detecting properties of multilayer MoSe2 crystal

The high photo responsive property and flexibility of tailoring the optical properties of the semiconducting layered transition metal dichalcogenides are appealing and makes them potentially suitable for the optoelectronic and photo detecting applications. In the present study molybdenum, diselenide (MoSe2) crystals were grown by direct vapor transport (DVT) technique in a dual zone horizontal furnace. To affirm the elemental composition and stoichiometric proportion of the as grown crystals, energy dispersive analysis of the x-ray was adopted. The surface morphological features of the grown crystals were investigated using light microscopy and scanning electron microscopy that attested the multilayer growth of crystals. The presence of single-crystalline phase and hexagonal structure was ascertained by employing transmission electron microscopy. The direct optical energy band gap of 1.42 eV was determined by UV-Visible spectroscopy. The Raman spectroscopy analysis carried out on the grown crystals revealed the presence of an A1g mode of vibration. Photo-detecting properties of the multilayer MoSe2 crystals were studied by exposing the basal plane of the photo-detecting sample by the polychromatic source of 70 mW/cm2 intensity at different biasing voltages from 1 V to 5 V respectively. The eminent sensing properties of the grown multilayered crystals are unveiled by the high photo responsivity 58.2 mA/Wm2 and specific detectivity 2.12 × 107 Jones. The effect of biasing voltage was prominently seen in the rise of photocurrent and detecting properties MoSe2 crystals.

A compact, dual-zone vertical tube furnace for the determination of tritium and carbon-14 in decommissioning wastes

A compact dual zone, two work-tube, vertical tube furnace system (Raddec Pyrolyser-Mini) has been designed for the determination of H-3 and C-14 in decommissioning wastes. An optimised methodology was developed following improvements to sample holder and bubbler trap design, sample loading and loading temperature, as well as length and style of heating programmes. A significant efficiency enhancement was obtained through ‘hot-loading’ of the sample into the furnace at 600 °C before finally ramping to 900 °C. Direct trapping of H-3 and C-14 in a scintillation vial located in a special anti-suck-back bubbler further improved operations, leading to a reduction in analysis time and measurement sensitivity. Co-trapping of the analytes and dual-label liquid scintillation counting also proved effective. Overall, the developed methodology led to a reduced analyte extraction/trapping time of 150 min whilst achieving limits of detection of <1 Bq/g. Validation of the procedure was assessed using a range of spiked matrices relevant to nuclear site decommissioning, reference materials and operationally-exposed materials. The compact size of this thermal extraction system is such that it allows for deployment in fume cupboards, gloveboxes and a mobile laboratory.

Impact of H 2 gas on the properties of MoS 2 thin films deposited by sulfurization of Mo thin films

MoS2 has gained tremendous interest due to its highlighting electronic and optoelectronic properties. In this work, an attempt has been made to develop a CMOS compatible process for the fabrication of a MoS2 thin film. In the first step, molybdenum (Mo) thin film was deposited on silicon substrate by RF magnetron sputtering. In the second step, chemical vapor deposition (CVD) was used for the synthesis of MoS2 using a custom-designed dual zone tubular furnace. The impact of hydrogen (H2) on the CVD growth of MoS2 thin film was studied with the mixture of H2 and argon (Ar) gas in 1:10 ratio. AFM and FESEM images revealed a uniform and smooth growth of MoS2 films using H2 as a reducing gas. Raman characteristics peaks, observed at 386 cm−1 and 408 cm−1, have confirmed the formation of MoS2 film, which corresponds to the hexagonal coordination (2H). The intensity of photoluminescence peak of MoS2 thin film is found to be increased with hydrogen treatment. Moreover, the impact of H2 gas was systematically studied on the electrical properties and a reduction in the carrier concentration of MoS2 was observed with a flow of 20 sccm H2. A detailed study on the impact of H2 gas and MoS2/Si heterojunction properties were also performed.

Mechanism of Overlying Crack-Stress Evolution When Mining on the Dual Fault Zone

To study the fissure-stress evolution law of overburden rock in the process of working face advancing in the dual fault area. This paper took the geological occurrence condition and actual mining situation of working face 21,129 of Tucheng mine as the engineering background. The method of similarity simulation combined with field measurement was adopted. The evolution law of the stope fissure field, the stress variation trend of roof fault, and migration characteristics of overlying strata in the process of stope mining through dual faults were studied. The results showed that: Dual faults had a large effective area on the surrounding rock of the stope, the surrounding rock movement in the affected area was intense. When the working face advanced to the fault F2 area, the energy generated during the surrounding rock movement of the fault F2 was transferred to the fault F1, which intensified the activity of the rock in the fault F1 area. The activation of the fault F2 caused the fissures in the surrounding rocks of the fault F1 to expand further. The surrounding rock of the stope changed from a single-fault action mode to a double-fault joint action mode. According to the degree of development of cracks in the roof of the overlying strata, the stope’s different positions were sorted from large to small as follows: fault activated fracture zone > central dual fault zone > open-off cut zone > middle of the non-fault affected zone. The field measured data showed that the area affected by the dual fault was composed of “high-pressure area” and “low-pressure area.” The working resistance value of hydraulic support was higher than that of the non-fault affected area. The law of fracture development and distribution in overlying strata of stope in similarity simulation experiments were consistent with the law of roof pressure measured in the field.

A tourist typology of online and face-to-face social contact: Destination immersion and tourism encapsulation/decapsulation

The sense of tourism encapsulation/decapsulation is increasingly determined by the level and type of connectivity enabled by advanced Information Communication Technology (ICT). This study explores tourists' online and face-to-face social contacts and their effects on travel experiences. A six-fold tourist typology is established, namely: Disconnected Immersive Traveller, Digital Detox Traveller, Diversionary Traveller, Dual Zone Traveller, Daily Life Controller and Social Media Addict. A contact–immersion nexus is also developed to indicate the attachment tendencies of different tourist types between their home and away zones. Theoretical contributions and practical implications are discussed.

Growth and application of WSe2 single crystal synthesized by DVT in thin film hetero-junction photodetector

Tungsten di-selenide (WSe2) belonging to the family of layered transition metal di-chalcogenides (TMDCs) is at present widely used in optoelectronic devices due to their adequate energy band gap suitable for photosensing applications. In the present investigation, WSe2 single crystals are grown by direct vapor transport (DVT) technique in a dual zone horizontal furnace maintaining a temperature difference of 50 K between source zone (SZ) and growth zone (GZ). The crystals thus obtained were thin, shiny and with an average thickness of 30 mm. The surface topography of crystals studied by optical microscope revealed hexagonal spirals on the crystal surface which seemed to arise due to screw dislocation defect. The structural properties of the as grown crystals studied by powder X-ray diffraction (XRD) elucidated good crystallinity, hexagonal structure and confirmed the orientation of crystals along crystallographic c-axis. P-type semiconductor nature of the crystals was affirmed by thermoelectric power (TEP) measurement. Optical and vibrational properties of the grown crystals were studied by UV–Visible, photoluminescence (PL) and Raman spectroscopy. An optical direct band gap of 1.41 eV was determined for the crystals which were micromechanically exfoliated upto few layers. The excitonic mechanism of the grown WSe2 crystal was explained by PL spectroscopy. The results of Raman spectroscopy disclosed A1g and E2g vibrational modes present in the crystals. The current–voltage characteristics of nSnSe/pWSe2 hetero-structure studied using Keithley 2400 SMU showed rectification behavior at low bias voltage in dark and illuminated conditions. The diode parameters like ideality factor and barrier potential were determined to be 2.54 and 0.4 eV, respectively, by following conventional lnI–V method. The photodetection properties of the fabricated device were studied using a Laser source (670 nm) having an intensity of 3 mWcm−2at different bias voltage ranging from 0.3 V to 3 V. Parameters such as responsivity, detectivity and external quantum efficiency (EQE) were calculated to substantiate the excellent detection properties shown by the prepared photodetector using time resolved pulsed photoresponse. Value of responsivity and EQE increased from 42.22 mA W−1 to 533.77 mA W−1 and 7% to 95%, respectively, with increase in bias voltage from 0.3 V to 3 V. Also, detectivity values were found to be of the order of 107 Jones.

Numerical solution for thermodynamic model of charge-discharge cycle in compressed hydrogen tank

The safety and convenience of hydrogen storage are significant for fuel cell vehicles. Based on mass conservation equation and energy conservation equation, two thermodynamic models (single zone model and dual zone model) have been established to study the hydrogen gas temperature and tank wall temperature for compressed hydrogen storage tank. With two models, analytical solution and Euler solution for single zone (gas zone) charge-discharge cycle have been compared, Matlab/Simulink solution and Euler solution for dual zone (gas zone, wall zone) charge-discharge cycle have been compared. Three charge-discharge cycle cases (Case 1, constant inflow temperature; Case 2, variable inflow temperature; Case 3, constant inflow temperature variable outflow temperature) and two compressed hydrogen tanks (Type III 25L, Type IV 99L) charge-discharge cycle are studied by Euler method. Results show Euler method can well predict hydrogen temperature and tank wall temperature.

A dual zone thermodynamic model for refueling hydrogen vehicles

With the simple structure and quick refueling process, the compressed hydrogen storage system is currently widely used. However, thermal effects during charging-discharging cycle may induce temperature change in storage tank, which has significant impact on the performance of hydrogen storage and the safety of hydrogen storage tank. To address this issue, we once propose a single zone lumped parameter model to obtain the analytical solution of hydrogen temperature and use the analytical solution to estimate the hydrogen temperature, but the effect of the tank wall is ignored. For better description of the heat transfer characteristics of the tank wall, a dual zone (hydrogen gas and tank wall) lumped parameter model will be considered for widely representation of the reference (experimental or simulated) data. Now, we extend the single zone model to the dual zone model which uses two different temperatures for gas zone and wall zone. The dual zone model contains two coupled differential equations. To solve them and obtain the solution, we use the method of decoupling the coupled differential equations and coupling the solutions of the decoupled differential equations. The steps of the method include: (1) Decoupling of coupled differential equations; (2) Solving decoupled differential equations; (3) Coupling of solutions of differential equations; (4) Solving coupled algebraic equations. Herein, three cases are taken into consideration: constant inflow/outflow temperature, variable inflow/outflow temperature and constant inflow temperature and variable outflow temperature. The corresponding approximate analytical solutions of hydrogen temperature and wall temperature can be obtained. The hydrogen pressure can be calculated from the hydrogen temperature and the hydrogen mass using the equation of state for ideal gas. Besides, the two coupled differential equations can also be solved numerically and the simulated solution can also be obtained. This study will help to set up a formula based approach of refueling protocol for gaseous hydrogen vehicles.

3d transition metals and oxides within carbon nanotubes by co-pyrolysis of metallocene & camphor: High filling efficiency and self-organized structures

We demonstrate that a single zone furnace with a modified synthesis chamber design is sufficient to obtain metal (Fe, Co or Ni) filled carbon nanotubes (CNT) with high filling efficiency and controlled morphology. The samples are synthesized by pyrolysis of metallocenes, a technique that otherwise requires a dual zone furnace. The respective metallocenes in all three cases are sublimed in powder form, a crucial factor for obtaining high filling efficiency. While Fe@CNT is routinely produced using this technique, well-formed Ni@CNT or Co@CNT samples are reported for the first time. This is achieved by sublimation of nickelocene (or cobaltocene) in combination with ‘camphor.’ Ni or Co@CNT exhibit some of the highest saturation magnetization (Ms) values, at least an order of magnitude higher than that reported earlier. The results elucidate on why Ni or Co@CNT are relatively difficult to obtain by pyrolyzing powder metallocene alone. A systematic variation of synthesis parameters provides insights for obtaining narrow length and diameter distribution with reduced residue particles outside the filled CNT - factors important for device - related applications. Finally, the utility of this technique is demonstrated by obtaining highly aligned forest of Fe2O3@CNT, wherein Fe2O3 is a functional magnetic oxide relevant to spintronics and battery applications.

Modeling hydrogen production in a catalytic-inert packed bed reactor by rich combustion of heavy fuel oil

This work presents simulation results for the production of hydrogen by the rich combustion of heavy fuel oil in a dual zone packed bed reactor. The first zone provides catalytic-thermal cracking of the fuel and is followed by a second zone for partial oxidation reforming of the cracked products. The kinetic model for the heavy fuel oil reactions in the catalytic zone uses decalin as a model compound. The partial oxidation reforming zone uses model compounds for the product groups formed from decalin cracking, and uncracked decalin. The hybrid reactor model is compared to results from a model of an inert (non-catalytic) porous media reactor. The work considers equivalence ratios from 1 to 2, filtration velocities between 15.0 and 65.5 cm/s, heat loss from 10 to 108% and particle diameter between 3 and 7 mm, and evaluates their effect on conversion. The simulations with the hybrid reactor model, in slightly rich conditions (equivalence ratio = 1.3) and constant filtration velocity of 19.3 cm/s deliver maximum hydrogen production for an optimal length of the intermediate zone. Considering this optimization: the total energy conversion efficiencies improve with the increase of the equivalence ratio due to the presence of hydrocarbon species generated by the cracking process. It is observed that the hybrid reactor model makes a better use of vaporized fuel, compared to a model for an inert packed bed reactor, when the deposits of carbonaceous material in the latter exceed 7.4%.

Inducing factors and frequency of combustion knock in hydrogen internal combustion engines

Hydrogen is a promising energy carrier, and the port fuel injection (PFI) is a fuel-flexible, durable, and relatively cheap method of energy conversion. However, combustion knock as an abnormal combustion phenomenon does not only limit the brake torque and thermal efficiency, but also breaks the piston or engines. This paper uses a four-stoke cycle, displacement of 2.0 L PFI hydrogen internal combustion engine and a calculated model to study the inducing factors and frequency of combustion knock. Results showed that combustion knock occurs at relatively higher engine speed (more than 3000 r/min) than the engine speed occurring knock of gasoline engine. The calculated average temperatures of air–fuel mixture at the end of combustion using thermodynamics dual zone model fall in the range of 1000–1100 K for hydrogen engines, which are higher than gasoline ones (about 200 K). Knock and the other abnormal combustion phenomena (backfire and pre-ignite) interact with each other. When the backfire generates, the components in the cylinder will be heated. In the next cycle, the components of the cylinder will release heat to the intake, which can increase the initial temperature at ignition. The high initial temperature will lead to the combustion knock. Otherwise, because of the combustion knock, the temperatures of cylinder components will increase, which generates hot spots and ultimately causes pre-ignite and backfire. Through the figures of Fast Fourier Transform (FFT) amplitude, the frequency of hydrogen engines is higher than gasoline ones for every kind of mode. The pressure waves of combustion knock spread with radial direction for light combustion knock and with circumferential direction for heavy combustion knock. These conclusions can be used to explore the working conditions close to combustion knock to achieve higher thermal efficiency and provide a guidance to detect the knock in hydrogen engine.

16-60: A New Approach to analyze ICD therapy Efficacy. Single-Centre Experience of Discovery™ Link TachyMed (Medtronic, USA)

The goal: to analyze an ICD therapy efficacy using an application Discovery™ Link TachyMed (Medtronic, USA). Materials and Methods: We enrolled 154 patients connected to the remote monitoring network Carelink (Medtronic, USA) who had an implanted dual (46) and triple chamber ICDs (108). Device programming parameters and intracardiac electrograms were studied. To carry out quantitative analysis of ICD therapy efficacy an application Discovery™ Link TachyMed was used. Statistical data are presented as Median (IQR 25%; 75%). Results: A dual zone ICD programming is frequently used (68%) in our center. A choice of single or triple ICD configuration is made rarely (in 22% and 10%, respectively). A zone of slow VT (sVT) corresponds to 179 (168; 182) bpm. A zone of fast VT (fVT) is programed in the range over 182 (176; 240) bpm and a zone of VF is detected in case of tachycardia equal or above 200 (188; 200) bpm. In most cases standard manufacturer discrimination algorithm is used. 690 episodes of VT were analyzed: 43 in VF zone (11 patients), 565 (12 patients) and 82 episodes (6 patients) in sVT and fVT zones respectively. ATP strategy was used in 78% cases (538 VT events). It was effective in 85% of initial VTs. These episodes were frequently referred to sVT and fVT. In 11% of analyzed VTs (76 events) a sinus rhythm was restored after ICD shock. It was usually due to VF events detection (75%). The vast majority of ICD shocks were delivered with submaximal values of energy (less than 35 Joules). Other episodes stopped spontaneously. Inappropriate shocks were delivered in 8 patients: in 5 of them due to atrial flutter with 1:1 conduction, in 2 patients because of atrial fibrillation with fast ventricular rate. In 1 case an electrical noise detected by a defibrillation lead was a reason for an appropriate shock. Conclusions: A low percent of inappropriate shocks was registered (7%). In most cases VT episodes were stopped by ATP, in cases of ICD shocks low values of energy were effective. Remote monitoring system provides facilities for early identification of the reasons of inappropriate ICD therapy. Discovery™ Link TachyMed application allows to carry out a quantitative analysis of ICD therapy efficacy which is especially necessary in centers with a high volume of ICD implantations.