Sandy Hardian Susanto Herho

TRISIKON (tiga situasi dan kondisi, three situations and conditions) is a directorial principle from Indonesian expanded cinema that composes three visual modes, documentation footage, animation, and live action, into one work and reads their collision as a dialectic between creative uncertainty and compositional order. Developed through practice-based studies, it has had no quantitative formalization. Here the three modes are placed on the cyclically symmetric axes of the Thomas flow, and the dialectic is identified with a single dissipation parameter that carries the flow between an ordered regime and a chaotic one. The structure is fixed by exact results proved here: the flow is dissipative, with a bounded absorbing set and a compact global attractor; it is equivariant under cyclic permutation of its axes; it has a saddle at the origin; and it contracts phase-space volume at a constant rate. Consequently its Lyapunov exponents sum to that contraction rate for every invariant measure, which also serves as an internal check of the computation. Each regime is characterized by the Lyapunov spectrum with its dimension and entropy rate, by a Gaussian and a nonparametric differential entropy, by the permutation entropy with its statistical complexity, and by an order parameter that provably vanishes when the symmetry holds. Four cases, an ordered baseline, a balanced breathing, a deconstructive regime, and a symmetry-broken mode-dominance regime, are separated consistently by every diagnostic. The formalization is a shared language between weak-chaos theory and the aesthetics of expanded cinema, not an empirical claim about film practice.

Scuba divers blow bubble rings, hollow vortex rings with a gas core that expands as the ring rises because the water pressure drops with every meter of ascent. Classical theory keeps the gas volume fixed and treats only level rings, and the one earlier estimate of the expansion, for a laboratory tank, found it small. Here the ring is modeled as a thin hollow vortex ring with a core that obeys Boyle's law and a motion set by the Kelvin impulse balance of a massless bubble, and this planar model is tested against a 3D vortex filament model. The ring radius has an exact solution in exponential integrals that holds for any tilt, and the extra growth relative to a ring of constant gas volume depends on a single release pressure number. This gain is near one in a tank but reaches 1.38 for release at 10 m and 1.98 at 40 m. A reference ring holding 10 mL of gas and released at 10 m grows from 5 to 18.5 cm in radius, compared with 14.8 cm at constant volume. Because its horizontal impulse is conserved, a tilted ring levels faster than predicted for a core that carries axial flow; a ring released 30 degrees from level ends nearly level after drifting 1.44 m sideways. Long bending waves decay as the ring grows. Along these trajectories, a viscous capillary stability criterion limits intact ascent to release depths of about 10 m. The two models agree to the expected order in the core slenderness.

We present antasena, an open-source Python library for calculations that underlie diving with nitrox, oxygen-nitrogen mixtures richer in oxygen than air. It computes depth limits, equivalent depths, inert-gas uptake, no-decompression limits, staged decompression schedules, central-nervous-system and pulmonary oxygen exposure, real-gas cylinder contents, and partial-pressure blending, and its command-line and desktop interfaces display the derivation of every result with the user’s inputs substituted. Each working equation is derived from the three-dimensional momentum balance of a fluid at rest, the advection-diffusion equation for a dissolved gas in perfused tissue, and the Helmholtz free energy of a gas mixture, with every reducing assumption stated. Because a dive plan is a sequence of segments of fixed gas and linearly varying depth, tissue tensions, oxygen doses, and gas consumption admit closed forms without time stepping. An independent re-implementation reproduces the closed-form tensions to within relative differences of 5 × 10^{−13} against fourth-order Runge-Kutta integration and 9 × 10^{−16} against 60-digit arithmetic, whereas the textbook form loses digits to cancellation on short segments. The analysis indicates that the classical equivalent air depth is shallower than its alveolar-consistent counterpart by 6 to 15 cm, that the textbook blending formula yields fills about 0.3 percentage points richer than intended for a 32% mixture at 200 bar, and that ideal-gas planning overstates the usable gas of an air cylinder filled to 232 bar by about 5%. All 79 independent checks pass. The library serves teaching and planning and does not predict individual physiological risk.

Sedimentary rocks are the main archive of Earth history, yet most of the time they span is not represented by rock. Material deposited at any moment survives only if the depositional surface never later erodes below it, so the stratigraphic column keeps only the lowest levels that a fluctuating surface will reach in the future. We treat this rule as a filter on a randomly evolving surface and connect it to the statistical physics of records and first passage. The fraction of time that is preserved depends on a single ratio between the resolution of observation and a crossover time set by net accumulation and surface roughness. At fine resolution this dependence is universal, the same for erosion by many small events or by rare catastrophic ones, provided successive events are independent. The Sadler effect, the decline of apparent accumulation rate with measurement interval, is governed by the persistence of the surface and changes form only when erosion has memory. With net accumulation, the age of a column as a function of height advances in independent jumps, which yields the complete statistics of hiatuses and shows that the longest gap produced by ordinary fluctuations grows only slowly with the length of the record. The same description predicts that an astronomical cycle appears in depth broadened, shifted toward longer apparent periods, and coherent over a limited number of repetitions. These results provide null models for unconformities and quantitative limits on the timing information that sedimentary sequences retain.

Coral transplantation attaches fragments to a structure placed on the seabed, and that structure must stay put long enough for the fragments to fuse to it. We examine that requirement with an idealized model in which a transplant unit is a planar rigid body on a rigid bed under two unilateral frictional contacts, loaded through a Morison description of near-bed wave kinematics and integrated by a nonsmooth contact time-stepping scheme. No measurement enters the model and no coefficient is calibrated. Three closed-form results follow from the balance of forces at rest. Whether a unit slides or tips is decided by comparing the base half-width divided by the height at which the flow pushes hardest against the friction coefficient of the bed; lift cancels exactly, and no material or wave property enters. Material affects the thresholds only through the submerged weight, so changing it rescales every threshold by one factor and reorders nothing. A wave riding on a current drives a net drift per cycle rising as the square of the overshoot above threshold. Five reference structures carrying growing colonies are compared at four idealized Indonesian site classes. Every unit loses margin as its corals grow, so success in the biological sense erodes the margin that permitted it, and an internal solitary wave (ISW) at transplant depth triggers a sliding step rather than an overturning. Across samples varying every uncalibrated coefficient together, the ranking of the structures proves far firmer than the thresholds. The solver is verified against closed-form impact, sliding, and rocking results.

Tides entering a coastal aquifer weaken and lag the sea as they travel inland, and classical theory requires the two rates to be equal. Field records often show the amplitude decaying faster than the phase lag grows, which is usually attributed to geometry or leakage. We examine a third mechanism, the exchange of water between a conduit network and the matrix blocks it surrounds, and ask when this exchange makes the aquifer behave as a fractional medium in time. The study is purely theoretical. For each tidal constituent, the measured decay and lag are exactly equivalent to a complex storage capacity at that frequency, so a single constituent cannot separate memory from leakage. Passive storage exchange and leakage can never make the lag rate exceed the decay rate, and diffusive exchange with blocks of any sizes cannot reduce their ratio below a fixed bound close to two fifths. A power law distribution of block sizes produces a fractional medium over a band of frequencies, with an order between one half and one set by the exponent of the distribution. In the nonlinear unconfined aquifer, the period mean of the squared head is conserved with or without memory, and the mean rise of the water table depends on the decay rate alone. For a karstic reference aquifer, one month of four tidal constituents reliably separates memory from leakage even when the matrix stores a fifth as much water as the conduits. All closed forms are verified numerically.

Gas exhaled by open-circuit divers collects under the ceilings of submerged caves, migrates along the rock, and dislodges loose silt that then falls through the passage, a process that cave divers call percolation. This study develops an idealized model of the process. Buoyant gas under a self-affine rough ceiling is treated as a quasi-static sequence of pools that fill to their spill points, release gas that climbs to the next high point, and merge where their levels meet. Moving contact lines strip silt from the rock, and the released silt settles as a spectrum of grain sizes that reduces the distance at which a diver can see. The computation agrees exactly with an independent depression-filling algorithm, conserves gas volume to round-off, and reproduces the known exponents of invasion percolation in its capillary limit. A balance between the relief of the ceiling and its dip defines a pool scale that organizes where gas collects, and the area covered by gas from a single source grows more slowly than the volume supplied, as predicted by the self-affine geometry. The cutoff at the pool scale is soft, so large pools persist on steeper ceilings than the scale alone would suggest. In a reference passage, the lead diver of a team releases far more silt than the diver behind, and a team releases far less than the sum of its members acting alone, because the lead diver fills the pools and strips the paths that later divers reuse. This ordering holds across every detachment efficiency and ceiling geometry tested. Visibility toward the exit at eye level continues to decline for an hour or more after a team has passed, as fine silt descends from a nearly opaque layer beneath the ceiling. Absolute silt masses and sighting ranges depend on quantities that have not been measured in caves, and the results are best read as scaling relations and comparisons between scenarios.

Farmland loss around expanding Asian metropolitan regions is usually attributed to urban and industrial construction, and monitored by measuring built-up expansion. This study shows that in a coastal rice regency the dominant mechanism is different. Nine consecutive years of ten-metre annual land cover covering 2017 to 2025 were combined with the statutory regency spatial plan across 191,540 hectares and thirty sub-districts in Karawang, West Java, Indonesia’s foremost rice granary. Cropland declined by 6,952 hectares, or 6.0 per cent, at a Theil–Sen rate of 992 hectares per year, while built-up land grew by 5,208 hectares. Point-topoint transition accounting shows that conversion to water accounted for 4,485 hectares of cropland loss and conversion to builtup land for 4,468 hectares, two nearly equal pathways. The two are almost perfectly segregated in space. Nine coastal sub-districts, defined by their intersection with the coastal setback and protected mangrove designations, hold 39 per cent of the regency area and 47 per cent of its cropland, yet account for 76 per cent of all cropland loss and 97 per cent of cropland converted to water; their cropland fell by 9.6 per cent against 2.7 per cent inland, and their water area grew by 3,332 hectares. Inland sub-districts lost cropland almost exclusively to building. Only 55.6 per cent of built-up expansion complied with designations permitting construction, and river setbacks absorbed 1,121 hectares. Coastal cropland is therefore being converted into pond-capable water surface at a scale that spatial-planning monitoring does not record, creating both an unaccounted loss of food-crop land and an unplanned aquaculture resource whose management falls outside the instruments now applied to it.

A downward fin thrust near a cohesive seabed lofts sediment. Whether this cloud settles or organizes into a self-sustaining down-slope current determines if a diver loses visibility briefly or catastrophically. We reduce the layer-averaged balances of fluid mass, sediment mass, and momentum to a temporal slab of fixed thickness in the weakly entraining limit. This yields an autonomous planar vector field in dimensionless near-bed speed and suspended load, governed by three dimensionless groups: drag against settling, erosion strength, and near-bed concentration. The field possesses a quiescent equilibrium at the origin and, above a critical bed slope obtained in closed form as the ratio of near-bed concentration times drag-settling number to erosion-strength number, an interior saddle equilibrium. The saddle's stable manifold partitions the state space into basins of decay and unbounded growth, establishing the exact threshold between self-limiting and igniting disturbances. On a flat bed, the origin attracts globally for all admissible erosion laws. For representative silt, the ignition threshold is near a 17-degree bed angle. The closed-form structure is confirmed numerically to machine precision. A closure study demonstrates the critical slope is robust in existence but closure-dependent in value, identifying the linear erosion law as the conservative choice. The model thus isolates bed slope as the controlling parameter for ignition.

This study provides a statistical characterization of surface oceanographic variability in the Indonesian Maritime Continent (IMC) during the Last Glacial Maximum (LGM; 23-19 ka) and Late Holocene (LH; 4-0 ka). Using the lgmDA v2.1 paleoclimate data assimilation product, we analyzed sea surface temperature (SST), sea surface salinity (SSS), and seawater δ¹⁸O. Results indicate the LGM was significantly cooler, saltier, and isotopically enriched, with lower spatial heterogeneity compared to the LH. Comprehensive nonparametric testing confirmed these differences reflected fundamental changes in distributional properties, not merely mean-state shifts. The findings suggest a major oceanographic regime shift, likely driven by lower sea levels, a weakened Indonesian Throughflow (ITF), enhanced stratification, and a drier regional climate during the LGM. This work offers a statistical framework for understanding IMC sensitivity to glacial-interglacial forcing.